15.11.1: Innate Behavior - Biology

15.11.1: Innate Behavior - Biology

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Behavior is action that alters the relationship between an organism and its environment. Behavior may occur as a result of

  • an external stimulus (e.g., sight of a predator)
  • internal stimulus (e.g., hunger)
  • or, more often, a mixture of the two (e.g., mating behavior)

It is often useful to distinguish between

  • innate behavior = behavior determined by the "hard-wiring" of the nervous system. A salamander raised away from water until long after its siblings begin swimming successfully will swim every bit as well as they the very first time it is placed in the water. Clearly this rather elaborate response is "built in" in the species and not something that must be acquired by practice.
  • learned behavior = behavior that is more or less permanently altered as a result of the experience of the individual organism (e.g., learning to play baseball well).
  • However, careful analysis often reveals that any particular behavior is a combination of innate and learned components.

Examples of innate behavior:

  • taxes
  • reflexes
  • instincts


Some organisms respond to a stimulus by automatically moving directly toward or away from or at some defined angle to it. These responses are called taxes. They are similar to tropisms in plants except that actual locomotion of the entire organism is involved. Link to a detailed discussion.


The Withdrawal Reflex

When you touch a hot object, you quickly pull you hand away using the withdrawal reflex.

These are the steps:

  • The stimulus is detected by receptors in the skin.
  • These initiate nerve impulses in sensory neurons leading from the receptors to the spinal cord.
  • The impulses travel into the spinal cord where the sensory nerve terminals synapse with interneurons.
    • Some of these synapse with motor neurons that travel out from the spinal cord entering mixed nerves that lead to the flexors that withdraw your hand.
    • Others synapse with inhibitory interneurons that suppress any motor output to extensors whose contraction would interfere with the withdrawal reflex.

The Stretch Reflex

The stretch reflex is examined (with a diagram) on a separate page. Link to it.


Instincts are complex behavior patterns which, like reflexes, are inborn, rather inflexible, and valuable at adapting the animal to its environment. They differ from reflexes in their complexity. The entire body participates in instinctive behavior, and an elaborate series of actions may be involved.

The scratching behavior of a dog and a European bullfinch, shown here, is part of their genetic heritage. The widespread behavior of scratching with a hind limb crossed over a forelimb in common to most birds, reptiles, and mammals. (Picture courtesy of Rudolf Freund and Scientific American, 1958.) So instincts are inherited just as the structure of tissues and organs is. Another example.

  • The African peach-faced lovebird carries nesting materials to the nesting site by tucking them in its feathers.
  • Its close relative, the Fischer's lovebird, uses its beak to transport nesting materials.
  • The two species can hybridize. When they do so, the offspring succeed only in carrying nesting material in their beaks. Nevertheless, they invariably go through the motions of trying to tuck the materials in their feathers first.

Foraging Behavior

Foraging for food is a crucial behavior for animals. Like all behavior, it requires the interaction of many components. Nonetheless, it turns out that in some animals, at least, foraging behavior can be altered by a single gene.

Drosophila melanogaster

The discovery of the genetic control of foraging in Drosophila began with the observations of Marla Sokolowski when she was an undergraduate biology student at the University of Toronto.

She noticed that Drosophila larvae, feeding in her culture vessels, displayed one of two distinct feeding patterns:

  • "rovers" who moved rapidly over the surface of the culture medium
  • "sitters who fed at a much more leisurely pace

She went on to find that this "bimodal" pattern of behavior

  • continued when the larvae became adults
  • was present in populations of wild fruit flies, not just in her laboratory colonies

After further years of research, she has shown that the behavior is under the control of a single gene, named for ("foraging"). Two alleles are present, at almost equal frequencies, that is, for is polymorphic.

  • forR, which is dominant
  • fors, the recessive
  • About 70% of natural populations are rovers being either homozygous for forR or heterozygous (forR/fors).
  • Sitters are homozygous for fors

Both alleles encode a PKG, a protein kinase (an enzyme that attaches phosphate groups to target proteins) that is activated by the "second messenger" cyclic GMP (cGMP). The enzyme encoded by the forR allele is more active than that encoded by fors. She and her colleagues have succeeded in inserting forR DNA into sitters who promptly become rovers.

Why this polymorphism? Why should alleles for two such different behaviors be maintained at such high frequency in the population?

One possible answer: it permits the population to thrive under varying food conditions:

  • sitters are favored when food is abundant
  • rovers are favored when competition for food is strong, such as in crowded cultures


Honeybees have their version of the for gene, called Amfor ("Apis mellifera for"). It, too, encodes a cGMP-dependent protein kinase (PKG). When worker bees first hatch, they remain in the hive tending to various housekeeping chores, such as feeding the larvae. But when they are 2–3 weeks old, they leave the hive and begin foraging for nectar and pollen. This change in behavior coincides with the increased expression of Amfor. When newly-hatched workers are treated with cGMP, the amount of PKG in their brains goes up and they quickly begin foraging instead of doing housekeeping.

Interaction of Internal and External Stimuli

Instinctive behavior often depends on conditions in the internal environment. In many vertebrates courtship and mating behavior will not occur unless sex hormones (estrogens in females, androgens in males) are present in the blood. The target organ is a small region of the hypothalamus. When stimulated by sex hormones in its blood supply, the hypothalamus initiates the activities leading to mating. The level of sex hormones is, in turn, regulated by the activity of the anterior lobe of the pituitary gland.

The above figure outlines the interactions of external and internal stimuli that lead an animal, such as a rabbit, to see a sexual partner and mate with it.

Releasers of Instinctive Behavior

Once the body is prepared for certain types of instinctive behavior, an external stimulus may be needed to initiate the response. N. Tinbergen (who shared the 1973 Nobel Prize with Konrad Lorenz and Karl von Frisch) showed that the stimulus need not necessarily be appropriate to be effective.

  • During the breeding season, the female three-spined stickleback normally follows the red-bellied male (a in the figure) to the nest that he has prepared.
  • He guides her into the nest (b) and then
  • prods the base of her tail (c).
  • She then lays eggs in the nest.
  • After doing so, the male drives her from the nest, enters it himself, and fertilizes the eggs (d).
  • Although this is the normal pattern, the female will follow almost any small red object to the nest, and once within the nest, neither the male nor any other red object need be present.
  • Any object touching her near the base of her tail will cause her to release her eggs.

It is as though she were primed internally for each item of behavior and needed only one specific signal to release the behavior pattern. For this reason, signals that trigger instinctive acts are called releasers. Once a particular response is released, it usually runs to completion even though the stimulus has been removed. One or two prods at the base of her tail will release the entire sequence of muscular actions involved in liberating her eggs.

Chemical signals (e.g., pheromones) serve as important releasers for the social insects: ants, bees, and termites. Many of these animals emit several different pheromones which elicit, for example, alarm behavior, mating behavior, and foraging behavior in other members of their species.

The mammary glands of domestic rabbit mothers emit a pheromone that releases immediate nursing behavior by their babies (pups). A good thing, too, as mothers devote only 5–7 minutes a day to feeding their pups so they had better be quick about it.

The studies of Tinbergen and others have shown that animals can often be induced to respond to inappropriate releasers. For example, a male robin defending its territory will repeatedly attack a simple clump of red feathers instead of a stuffed robin that lacks the red breast of the males.

Although such behavior seems inappropriate to our eyes, it reveals a crucial feature of all animal behavior: animals respond selectively to certain aspects of the total sensory input they receive. Animals spend their lives bombarded by myriad sights, sounds, odors, etc. But their nervous system filters this mass of sensory data, and they respond only to those aspects that the evolutionary history of the species has proved to be significant for survival.

15.11.1: Innate Behavior - Biology

Behavior is the change in activity of an organism in response to a stimulus. Behavioral biology is the study of the biological and evolutionary bases for such changes. The idea that behaviors evolved as a result of the pressures of natural selection is not new. For decades, several types of scientists have studied animal behavior. Biologists do so in the science of ethology psychologists in the science of comparative psychology and other scientists in the science of neurobiology. The first two, ethology and comparative psychology, are the most consequential for the study of behavioral biology.

One goal of behavioral biology is to distinguish between the innate behaviors , which have a strong genetic component and are largely independent of environmental influences, from the learned behaviors , which result from environmental conditioning. Innate behavior, or instinct, is important because there is no risk of an incorrect behavior being learned. They are “hard wired” into the system. On the other hand, learned behaviors, although riskier, are flexible, dynamic, and can be altered according to changes in the environment.

This is not a reference to our behavior (although, of course, some people do act like animals). It is a reference to the fact that humans are biological creatures, as much as crocodiles, cougars, and capybara. We are the product of millions of years of evolution, our physical make-up changing to make us fitter to survive and reproduce.

However, although humans are animals, we also have something that no other animal has: the most complex social structure on Earth. We gather in families, tribes, clans, nations. We have an incredibly sophisticated method of interacting -- speech. We can communicate over time and distance through printing and broadcasting. Our memories are the longest, our interactions the most intricate, our perception of the world simultaneously the broadest and most detailed.

The combination of biology and society is what makes us what we are and do what we do. Biology guides our responses to stimuli, based on thousands of generations of ancestors surviving because of their responses. Our social structures dictate restrictions on and alterations in how we carry out our biological responses.

Neither biology nor society stands without the other. For some people, this is a contradiction -- either nature (biology) controls people, or nurture (society) does. But in fact we filter everything through both to determine how we react to stimuli. The following is a discussion of the two sides of human nature: first, the biological basis of our responses to the world around us, and second, the social factors that affect those responses and make us human.


The three main elements biology contributes to human behavior are: 1) self-preservation 2) the reason for self-preservation, reproduction and 3) a method to enhance self-preservation and reproduction, greed. I will discuss each in turn.

Self-preservation is keeping yourself alive, either physically or psychologically. The latter includes mentally or economically healthy. (Since human beings are very social creatures, we may also apply self-preservation to other people, such as our families. However, I will discuss that in the next chapter.)


A lioness slowly, stealthily, works through the tall grass toward the herd of wildebeest. A doe, unaware of the danger lurking in the grass, separates slightly from the herd. With a rush, the lioness bursts into a run to take down the doe. The startled doe bounds away, running and swerving, trying to escape. The lioness, unable to keep up the pace, gives up, and the doe escapes back into the herd.

A zebra is not so lucky, and the pride feasts.

The Donner Party was a group of settlers trekking to California in 1846. Trapped by snow in the Sierra Nevada Mountains , they survived as best they could. This included resorting to cannibalism when they ran out of food, eating the bodies of those who had died.

To be successful as a species, the members of that species must have a desire to survive long enough to pass on their genes to offspring. A species with a death-wish dies out rather quickly. Those species that don't die out have members that have devoted some attention to staying alive long enough to have young. It is from those individuals and therefore species that all living things are descended.

The desire to stay alive is an instinctive one, built into the psyche of the organism. The organism will seek those elements of its environment that will enhance its chances for survival. These include food, water, oxygen, and periods of rest to allow the body to repair any wear and tear on the tissues.

Alternately, it will avoid or evade those elements that might reduce its chances for survival. Such dangers include predators, starvation, dehydration, asphyxiation, and situations that can cause damage to the body.

These seek or avoid drives influence the behavior of organisms: iron seeking bacteria will move toward magnetism, gnus will migrate hundreds of miles to find new pastures, a human will resort to cannibalism an amoeba will flow away from an electric current, an antelope will run from a lion, a human will obey a killer or withstand torture.

The desire to stay alive is also a selfish instinct, since it is personal survival that the organism is seeking. The reason for that is explained under REPRODUCTION.

Survival Through Evolution

A phrase that has often been misquoted, "Survival of the Fittest," actually means survival of the fit. By fit, I mean an organism has those attributes that allow it to get the most out of its environment: gather food, drink, oxygen, rest, sex. The better it is at doing this, the more fit it is.

At this point I should discuss the niche. A niche is a position within an environment that calls for certain attributes to exploit that environment. An environment can contain any of a variety of elements: amount of water, from ocean to desert type of land, from marsh mud to solid rock amount of vegetation, from none (the Arctic and Antarctic) to abundant (rainforests). It can also contain animal life, from the tiniest insects to blue whales and everything in between. It is the combination and degree of each of these elements that create niches.

As an example, let's look at just one of these elements. Say there are many small animals, like mice, in an area. A small carnivore like a wildcat could find a lot of food. Thus, it would fit into this niche and thrive. However, when the number of mice decreases, the wildcat can find less food, and has a lesser chance of survival.

If the wildcat has competition from other small carnivores, like foxes, the one that is particularly good as a predator, through cunning or speed or some other attribute, will catch more food. This lessens the amount of food available for the competition, and thus drives the competition out. If the fox is better at catching mice (that is, more fit) than the wildcat, the wildcat will either die or have to move to another niche in which it will be the better predator.

On the other hand, if there are no small animals but many big animals, like antelope, neither a fox nor a wildcat would have much success preying on them. Thus, they wouldn't fit in such a niche. However, large carnivores such as lions would.

Of course, nothing stays the same forever. Niches alter through geologic, climatic and, in the present day, man-made changes in land, water and air. A volcano can create a new island. An ice age can lock up huge quantities of water in ice caps and glaciers, creating areas of land where oceans once rolled. Continental drift can push seabeds to the tops of mountains. Humans can chop down forests and build cities. All these changes alter the niches, the environmental conditions under which the life in those niches live.

Of course, this means the life has to change as well, to match the new conditions. If it doesn't, it dies. An example is a moth in England . It was originally a mottled white, which allowed it to blend into the light bark of the trees in its area. However, in the 19th century factories in this area began to belch out soot from their chimneys that settled on the trees, changing the tree bark from mottled white to mottled black. The moth could no longer blend in and thus was easy prey to birds. However, some of the moths were darker and thus less noticeable. After a few generations of these darker moths surviving and passing on their genes, the standard color changed to mottled black, and the moth, now blending into the dark bark, survives.

Note that such changes are not conscious decisions made by the organism: the moth did not say to itself, "The bark is getting dark--I'd better change color, too." It is simply that there are variations between individuals in any species (an advantage of sexual reproduction and its combining of genes). Some of those variations are detrimental: the dark moth variations were easy prey when the tree bark was light. However, as the conditions in a niche change, those same variations can become advantageous, enhancing rather than weakening chances for survival.

Such changes in an organism's physical characteristics are, of course, accidental. If no variations exist in a species that contribute to survival when conditions change, or if conditions change too quickly for advantageous variations to be passed on to enough descendants,(1) the species can die out.

Survival Through Strategy

Other changes in an organism can develop over time. These are survival strategies, rather than physical changes, that improve the organism's chances for survival. For example, some animals have perfected the technique of hibernating during periods when the food supply is low. Marmots have developed a social structure that provides lookouts who watch for predators and sound a warning when one appears. Prairie dogs dig their burrows with multiple entrances and exits so if a predator comes in one door, the dogs can leave through another.

These survival strategies are adaptations to niche conditions, but unlike physical changes are not necessarily genetic changes. Such strategies as hibernation, of course, require genes that alter the animal's physiology to slow heartbeat, lower body temperature, and otherwise decrease its metabolism. Others are instinctive, hardwired genetically into the animal's brain, such as a fawn's curling up and freezing when predators are about.

However, some survival strategies are learned behaviors. That is, the young learn them from older animals that learned them from their ancestors. For example, most predators teach their young the techniques of successful hunting. In general, it appears the higher the complexity of the nervous system of the animal, the more likely strategies are learned rather than instinctive. Sharks, with a relatively simple nervous system, hunt by instinct and need no instruction on how to go about it. Lions, with a complex system, must learn the techniques of stealth, stalk, and attack.

Again, in most animals, the strategies are not conscious decisions, but responses to stimuli such as hunger, thirst, asphyxiation, fear, or exhaustion. If conditions change so the instinctive strategy is dangerous rather than beneficial, the animal can die. For example, the fawn's freeze response to fear would be deadly if there was no cover to hide in while frozen. The musk ox strategy is to form a stationary circle with the young in the center and the older members facing outward, rather than running away. This is excellent against wolves, but deadly when faced with spears and guns (perfect, however, for the human survival strategy of group hunting with weapons). The musk ox cannot consciously decide that this strategy isn't working and that they must try another.

The combination of genetic and learned responses to stimuli creates an animal's reaction to stimuli. For example, the genetically dictated instinctive reaction to a threat to self-preservation is the "fight or flight" syndrome. When threatened, an animal undergoes several physiological changes that have become genetically hardwired into the animal's body. The changes include an increased rate of respiration to provide more oxygen to the muscles, an accelerated heart beat to speed up the blood flow, a lessening in sensitivity to pain, and changes in the blood stream, including an injection of adrenalin and diversion away from the organs to the muscles. These physiological changes prepare the animal to either fight for survival or run away from danger.

However, learned responses can mitigate the instinctive, depending on the complexity of the animal's nervous system. That complexity increases an animal's options in reacting to stimuli. For example, an amoeba will avoid an electric field automatically -- an instinctive reaction unmitigated by a survival strategy. A starving rat, however, will run across an electrified grid that gives it painful shocks if there is food on the other side. It can learn a survival strategy -- the shocks, though causing the instinctive fight-or-flight physiological changes, aren't going to kill it. Starvation will.


All the above applies to humans as much as any other animal: humans desire personal survival seek food, drink, rest, sex fit into niches must adapt to changing conditions.

Humans are subject to the same stimuli and reactions as any other animal. Hunger, thirst, asphyxiation, fear, and exhaustion are physical sensations that cause instinctive physical reactions. Most of these reactions are unpleasant, and people avoid the stimuli that cause them, or, if they're unavoidable, take actions to reduce them. Thus you eat when hungry, drink when thirsty, fight for air, run from dangerous situations, sleep. In any case, the reactions are good in that they tell you you're in a situation that could result in injury or death. These responses are instinctive, and we have no more control over them than we do over our eye color.

Actually, we do have control over our eye color. The reason we do is why our approach to self-preservation is different from all other creatures. We have a brain that is capable of perceiving and solving problems. We change our eye color with contact lenses. We react to a threatening situation through applying our brains to the problem and finding a solution to it.

The difference between humans and other animals is that, unlike any other animal (as far as we know), we can and do consciously respond or alter our response to a stimulus. The greatest example lies in the existence of amusement parks, where people deliberately subject themselves to stimuli that any other creature on earth would go to great lengths to avoid. Imagine, if you can, the reaction of a dog to a roller coaster. If it didn't leap out at the first movement, it would cringe in bottom of the car until it probably had a heart attack. Yet, humans go on such rides for fun, our minds accepting that the ride is safe, and thus control the terror such a thing would cause in any other creature.

Indeed, the physical manifestations of the stress of the workplace, such as ulcers, headaches, nervous breakdowns, is often considered a result of the fight or flight syndrome at work on the body, while the mind is required to remain under stimuli that no other creature would willing accept. For example, being bawled out by your boss would, in another animal, cause a fight or the chastised to run. Humans, though, stand, listen, nod their heads, say "yes, I understand" and go back to work (probably muttering uncomplimentary comments about the boss under their breath).

Even more, humans can alter rather than merely adapt to the environments in which we find ourselves to enhance our chances for survival. The invention of agriculture and the domestication of animals improved the food supply the building of dwellings enhanced shelter from the elements science and medicine have greatly increased human lifespan and the quality of that life. Human ingenuity has altered every aspect of the world to enhance the human life.(2)

However, humans live in an extremely complex society. Thus, self-preservation is a much more complicated proposition than among other animals. Eating to satisfy hunger is more than just finding proper vegetation or hunting shelter for rest and recuperation is more than finding a convenient cave or nest avoiding predators is difficult because it is often hard if not impossible to tell what is a predator (the only real predators on humans are other humans). Even avoiding dangerous situations (such as car crashes) is difficult because of human technology. Things can happen so quickly danger isn't apparent until it's too late to do anything about it.

To deal with the complexity, human society has become, to a large extent, an economic one. That is, the connections between unrelated people is often based on distribution of resources (related people connect more through personal attachment). I will discuss these social factors in human self-preservation in the next chapter.

The above quote is from the popular movie, WALL STREET , starring Michael Douglas. When it was spoken in the movie, it was used as an ironic counterpoint: the character who said it was very successful following the credo, but ultimately it was his downfall. The audience may have though it was poetic justice. The credo, however, is merely a statement of biological necessity.

Greed has an extremely negative connotation for most people. It conjures up images of Ebenezer Scrooge and Shylock, chortling over their gold and ignoring the plights and miseries of others. However, it is actually the gathering of resources, the more the better. Biologically, for any organism that is successful greed is good.

Any form of life must gather resources that allow it to survive and reproduce. The resources may be food, water, sunlight, minerals, vitamins, shelter. Without these things, the organism dies. Since the two most basic purposes of life are to live and to reproduce, it should do everything it can to avoid dying through a lack of resources.

Greed is one organism getting a larger piece of the pie, more of the necessary resources, than other organisms. For example, in the Amazonian rain forest, an occasional tree dies and falls. This leaves an opening to the sun in the continuous canopy of foliage. Plants and trees race each other to grow into that opening. The winners in the race fill the hole the losers die through lack of sunlight. (Attenborough, 1990) The greed for sunlight means life.

Again, as for self-preservation and sex, greed is an instinctive reaction. When presented with resources, the instinct is to grab them, use them, take advantage of them. This isn't a conscious decision. An animal, when starving, wants more food when thirsty, more water. If it means taking it from another animal, that's what it does if it can.

You may ask, what about those animals who feed their offspring, though they're starving themselves? Remember that the second purpose of life is to reproduce. This requires not only producing the young. Once it's born it must be kept alive until it's self-sufficient. If it dies, then all the time, effort and energy to produce it must be repeated to produce another one. However, once it reaches self-sufficiency the parent's genes will, most likely, be passed on to another generation. Keeping the offspring alive, even at the expense of the parent dying, is of paramount importance. Thus, a parent caring for its young at its own expense is not an act of selflessness it's an act of genetic selfishness.

You may also point out that humans avoid being greedy. In fact, being greedy is something that is scorned, something to be ashamed of. Once again, as for self-preservation and reproduction, it's because humans are unique -- we have a conscious mind that influences their biological instincts. How that works is the topic of the next chapter.


1There is a theory of critical mass, that the gene pool for a species must be large enough (that is, the breeding population must be large enough) to provide enough variations to counter adverse conditions or events. For example, the African cheetah population appears to be descended from only a few individuals apparently most of the species fell prey to a disease that only a few survived because of a genetic immunity. Those few represented a gene pool too small to provide much in the way of variation, and there is a fear that something, perhaps another disease to which the current population has no genetic immunity, will kill off the remaining cheetahs.

2 Of course, we can also argue that this same ingenuity has enhanced human life to the point that human life, and all other life on earth, is threatened. The human ability to alter the environment to help people survive has allowed so many people to survive that the Earth itself, which is need to support them, many not survive.

E3 Innate & Learned Behaviour

Cuckoos take advantage of reed warblers’ innate caring for chicks – to offload childcare!

TED Talk: I am my Connectome. How do we learn? How does that mould who were are? What is going on inside that brain of ours? Find out:

Here’s a nice TED Talk on how games reward the brain. Think about how your game-playing (or other immersive pastimes) motivate you through rewards and reinforcement.

Which is more intelligent – a dog or a baby?

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Hi Stephen,
I use your powerpoints and Essential Bio study guides to review in my Bio HL class…THANK YOU! I’m starting to teach the Option E this week, but the files on slideshare for all except the E3 topic are damaged and I couldn’t download them. Could you email them to me or I guess try to re-upload to slideshare?
I’d really appreciate it, I love all of your links and photos and haven’t taught this Option in the past so need all the resources I can get my hands on.
Thanks so much,

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3. Innateness and genetics

During the 2008 US presidential election journalists frequently referred to a candidate's characteristic beliefs or attitudes as &lsquopart of their political DNA&rsquo. This is an example of how in contemporary English &lsquoin the DNA&rsquo or &lsquoin the genes&rsquo has come to replace older phrases like &lsquoin the blood&rsquo. But if genetics can be used to elucidate the innate/acquired distinction it is certainly not because some traits, the innate ones, are caused by the genes whilst others, the acquired ones, are caused by the environment. While the difference between two individuals can be caused by a genetic or an environmental difference between them, the development of any trait in an individual depends on both genes and environment. Every aspect of development, including learning, consists in the regulated expression of the genome. Conversely, innumerable aspects of the environment are required at each stage in the life of the organism to keep development on its normal course, or, in other words, to ensure that the right genes are expressed in the right cells at the right time. Thus, all traits develop through the interaction of genome and environment. Philip Kitcher has referred to this as the &lsquointeractionist consensus&rsquo (Kitcher 2001).

But if all traits depend on genes, it may still be that some traits depend on them in a special way. If asked about phrases like &lsquoin the DNA&rsquo or &lsquoin the genes&rsquo, most people would probably refer to the idea that the genes contain instructions or a program. After all, everyone knows that there is a genetic code, so it must be coding for something. Perhaps genes &lsquocode for&rsquo innate traits but not for acquired ones. However, as Peter Godfrey-Smith has noted, &lsquoAll the genes can code for, if they code for anything, is the primary structure (amino acid sequence) of a protein&rsquo (Godfrey-Smith 1999, 328). Considered as a language, the genetic code can only refer to the twenty-three standard amino acids and can only say which order to put them in. The only exceptions to this are the &lsquostart&rsquo and &lsquostop&rsquo codons which affect where DNA transcription begins and ends. Many other things happen as a downstream causal consequence of the order of amino acids, but to paraphrase Godfrey Smith's argument, genes do not &lsquocode for&rsquo these downstream causal consequences for the same reason that President Nixon's order to cover up the Watergate scandal was not an &lsquoorder&rsquo to get him impeached by Congress. &lsquoCoding for&rsquo, like &lsquoordering&rsquo and other semantic locutions, is not merely another name for &lsquocausing&rsquo. The idea that the &lsquogenetic program&rsquo or &lsquogenetic instructions&rsquo for phenotypes are literally written in the genetic code is a continuing barrier to the public understanding of genetics, one that is reinforced every time a journalist reports that scientists have &lsquodecoded&rsquo the gene for something. In reality there are no tiny &lsquotraitunculi&rsquo hidden in the genome awaiting a sufficiently powerful genetic microscope to read them (Schaffner 1998).

But although the sequences of nucleotides in the genome do not literally &lsquocode for&rsquo phenotypic traits, they are, of course, amongst the causes of phenotypic traits. Several philosophers and scientists have introduced senses of &lsquogenetic information&rsquo based on these causal relationships in order to explicate the intuitive idea that genes carry information about phenotypes. These proposals are discussed in more detail in the entry Biological information. Here I will simply make two points about these proposals. The first point is that there are some very straightforward senses in which genes &lsquocarry information&rsquo about phenotypes. The human Y chromosome carries information about sex in the same way that &lsquosmoke means fire&rsquo: one can be predicted from the other. In addition, the SRY region on the Y-chromosome is an adaptation for making organisms into males, so we can apply a version of &lsquoteleosemantics&rsquo, an approach which defines information in terms of adaptation, to this piece of DNA (Millikan 1984 Sterelny, Dickison et al. 1996 and see the entry on teleological theories of mental content). The second point is that these straightforward senses of &lsquoinformation&rsquo also seem to be applicable to environmental causes in development (Oyama 1985 Griffiths and Gray 1997 Griffiths and Knight 1998 Griffiths and Gray 2005). Mammals have a chromosomal system of sex-determination. But many reptiles use temperature, an environmental signal, to switch genetically identical eggs between male or female developmental pathways. Other reptiles have a genetic system which can be overridden by an environmental signal. Some fish even switch sex in adulthood in response to environmental cues. These environmental signals carry information about sex in the unproblematic &lsquosmoke means fire&rsquo sense. Moreover, the behaviours that parents use to give appropriate cues to their eggs, and some of the products of those behaviours, such as nests of rotting vegetation which maintain a suitable temperature range, are designed by natural selection to ensure the correct sex-ratio in offspring, so the teleosemantic program can be applied to them too. The idea that genes &lsquocarry information&rsquo about phenotypes in a special sense which distinguishes them from other causes is not the piece of common-sense it is often taken to be, but rather a highly contested idea that is the focus of current research in the philosophy of biology (Oyama 1985, Maynard Smith 2000, Griffiths 2001, Robert 2004).

If all traits are caused by both genetic and environmental factors, then reconstructing the innate/acquired distinction in genetic terms means distinguishing different ways in which genes interact with the environment. The pattern of interaction between gene and environment is commonly represented using &lsquonorms of reaction&rsquo &mdash graphical representations of a phenotypic variable as a function of genotypic and environmental variables. These diagrams were introduced at around the same time as the idea of the gene and the distinction between genotype and phenotype (Sarkar 1999) and have long been advocated as the clearest way to think about the role of genes in development (Hogben 1933 Lewontin 1974 Gottlieb 1995 Kitcher 2001). Suppose, for example, that with respect to some environmental variable (E) an organism with a given genotype (G1) will develop the same phenotype (P) way no matter what value the environmental variable takes (Figure 1).

Figure 1. A norm of reaction in which the phenotype P is &lsquogenetically determined&rsquo

If a norm of reaction has this shape, we can say that P is &lsquogenetically determined&rsquo even though it has an environmental factor as one of its causes. Philip Kitcher suggests that some norms of reaction may have this form, but only in some limited, but perhaps contextually important, range of environments (Kitcher 2001). For example, a disease caused by the loss of one or both normal copies of a gene might develop in every environment except those specifically structured as clinical interventions to cure the disease.

Another norm of reaction is one in which genetic and environmental factors interact &lsquoadditively&rsquo (Figure 2). Genotype makes a constant difference across some range of environment. While the genetic variable does not determine the actual value of the trait in each individual, it does determine the differences between individuals. Moreover, when the norms of reaction have this form, heritability scores become relevant to the question of whether and how much a phenotype can be altered by environmental intervention, as discussed in the previous section. A famous diagram in the early days of behaviour genetics depicted the relationship between IQ (P), genotype (G) and the &lsquoenrichment&rsquo of the environment (E) as having roughly this form (Gottesman 1963a). If correct, this would mean that educational enrichment would cause everyone to get higher test scores, but would not change the ordering of their scores.

Figure 2. Purely additive interaction between genotype and environment

In perhaps the most famous paper on this topic the geneticist Richard Lewontin (1974) argued that actual norms of reaction are likely to be non-additive (Figure 3). In that case, it makes no sense to talk of a particular genotype &lsquodetermining&rsquo a phenotypic difference. Genotype and environment jointly determine the outcome in the straightforward sense that the effect of each factor on the outcome is a function of the particular value taken by the other factor. Whether norms of reaction are typically non-additive and exactly what this implies is the subject of an extensive scientific and philosophical literature on &lsquogene-environment interaction&rsquo, as discussed in the previous section.

Figure 3. Non-additive interaction between genotype and environment

Philip Kitcher has argued that &lsquogenetic determinism&rsquo should be understood as the claim that many norms of reaction have roughly the &lsquodeterminist&rsquo shapes depicted in Figures 1 and 2 (for an alternative view, see Griffiths 2006). In Section 4.3 I discuss a recent proposal to define &lsquoinnate&rsquo in the same spirit.

Interaction of Internal and External Stimuli

In many vertebrates courtship and mating behavior will not occur unless sex hormones (estrogens in females, androgens in males) are present in the blood.

The target organ is a small region of the hypothalamus. When stimulated by sex hormones in its blood supply, the hypothalamus initiates the activities leading to mating.

The level of sex hormones is, in turn, regulated by the activity of the anterior lobe of the pituitary gland.

The drawing outlines the interactions of external and internal stimuli that lead an animal, such as a rabbit, to see a sexual partner and mate with it.


E. O. Wilson defined sociobiology as "the extension of population biology and evolutionary theory to social organization". [3]

Sociobiology is based on the premise that some behaviors (social and individual) are at least partly inherited and can be affected by natural selection. [4] It begins with the idea that behaviors have evolved over time, similar to the way that physical traits are thought to have evolved. It predicts that animals will act in ways that have proven to be evolutionarily successful over time. This can, among other things, result in the formation of complex social processes conducive to evolutionary fitness.

The discipline seeks to explain behavior as a product of natural selection. Behavior is therefore seen as an effort to preserve one's genes in the population. Inherent in sociobiological reasoning is the idea that certain genes or gene combinations that influence particular behavioral traits can be inherited from generation to generation. [5]

For example, newly dominant male lions often kill cubs in the pride that they did not sire. This behavior is adaptive because killing the cubs eliminates competition for their own offspring and causes the nursing females to come into heat faster, thus allowing more of his genes to enter into the population. Sociobiologists would view this instinctual cub-killing behavior as being inherited through the genes of successfully reproducing male lions, whereas non-killing behavior may have died out as those lions were less successful in reproducing. [6]

The philosopher of biology Daniel Dennett suggested that the political philosopher Thomas Hobbes was the first sociobiologist, arguing that in his 1651 book Leviathan Hobbes had explained the origins of morals in human society from an amoral sociobiological perspective. [7]

The geneticist of animal behavior John Paul Scott coined the word sociobiology at a 1948 conference on genetics and social behaviour which called for a conjoint development of field and laboratory studies in animal behavior research. [8] [9] With John Paul Scott's organizational efforts, a "Section of Animal Behavior and Sociobiology" of the Ecological Society of America was created in 1956, which became a Division of Animal Behavior of the American Society of Zoology in 1958. In 1956, E. O. Wilson came in contact this emerging sociobiology through his PhD student Stuart A. Altmann, who had been in close relation with the participants to the 1948 conference. Altmann developed his own brand of sociobiology to study the social behavior of rhesus macaques, using statistics, and was hired as a "sociobiologist" at the Yerkes Regional Primate Research Center in 1965. [9] Wilson's sociobiology is different from John Paul Scott's or Altmann's, insofar as he drew on mathematical models of social behavior centered on the maximisation of the genetic fitness by W. D. Hamilton, Robert Trivers, John Maynard Smith, and George R. Price. The three sociobiologies by Scott, Altmann and Wilson have in common to place naturalist studies at the core of the research on animal social behavior and by drawing alliances with emerging research methodologies, at a time when "biology in the field" was threatened to be made old-fashioned by "modern" practices of science (laboratory studies, mathematical biology, molecular biology). [10] [9]

Once a specialist term, "sociobiology" became widely known in 1975 when Wilson published his book Sociobiology: The New Synthesis, which sparked an intense controversy. Since then "sociobiology" has largely been equated with Wilson's vision. The book pioneered and popularized the attempt to explain the evolutionary mechanics behind social behaviors such as altruism, aggression, and nurturance, primarily in ants (Wilson's own research specialty) and other Hymenoptera, but also in other animals. However, the influence of evolution on behavior has been of interest to biologists and philosophers since soon after the discovery of evolution itself. Peter Kropotkin's Mutual Aid: A Factor of Evolution, written in the early 1890s, is a popular example. The final chapter of the book is devoted to sociobiological explanations of human behavior, and Wilson later wrote a Pulitzer Prize winning book, On Human Nature, that addressed human behavior specifically. [9] [11]

Edward H. Hagen writes in The Handbook of Evolutionary Psychology that sociobiology is, despite the public controversy regarding the applications to humans, "one of the scientific triumphs of the twentieth century." "Sociobiology is now part of the core research and curriculum of virtually all biology departments, and it is a foundation of the work of almost all field biologists" Sociobiological research on nonhuman organisms has increased dramatically and continuously in the world's top scientific journals such as Nature and Science. The more general term behavioral ecology is commonly substituted for the term sociobiology in order to avoid the public controversy. [12]

Sociobiologists maintain that human behavior, as well as nonhuman animal behavior, can be partly explained as the outcome of natural selection. They contend that in order to fully understand behavior, it must be analyzed in terms of evolutionary considerations.

Natural selection is fundamental to evolutionary theory. Variants of hereditary traits which increase an organism's ability to survive and reproduce will be more greatly represented in subsequent generations, i.e., they will be "selected for". Thus, inherited behavioral mechanisms that allowed an organism a greater chance of surviving and/or reproducing in the past are more likely to survive in present organisms. That inherited adaptive behaviors are present in nonhuman animal species has been multiply demonstrated by biologists, and it has become a foundation of evolutionary biology. However, there is continued resistance by some researchers over the application of evolutionary models to humans, particularly from within the social sciences, where culture has long been assumed to be the predominant driver of behavior.

Sociobiology is based upon two fundamental premises:

  • Certain behavioral traits are inherited,
  • Inherited behavioral traits have been honed by natural selection. Therefore, these traits were probably "adaptive" in the environment in which the species evolved.

Sociobiology uses Nikolaas Tinbergen's four categories of questions and explanations of animal behavior. Two categories are at the species level two, at the individual level. The species-level categories (often called "ultimate explanations") are

  • the function (i.e., adaptation) that a behavior serves and
  • the evolutionary process (i.e., phylogeny) that resulted in this functionality.

The individual-level categories (often called "proximate explanations") are

Sociobiologists are interested in how behavior can be explained logically as a result of selective pressures in the history of a species. Thus, they are often interested in instinctive, or intuitive behavior, and in explaining the similarities, rather than the differences, between cultures. For example, mothers within many species of mammals – including humans – are very protective of their offspring. Sociobiologists reason that this protective behavior likely evolved over time because it helped the offspring of the individuals which had the characteristic to survive. This parental protection would increase in frequency in the population. The social behavior is believed to have evolved in a fashion similar to other types of nonbehavioral adaptations, such as a coat of fur, or the sense of smell.

Individual genetic advantage fails to explain certain social behaviors as a result of gene-centred selection. E.O. Wilson argued that evolution may also act upon groups. [13] The mechanisms responsible for group selection employ paradigms and population statistics borrowed from evolutionary game theory. Altruism is defined as "a concern for the welfare of others". If altruism is genetically determined, then altruistic individuals must reproduce their own altruistic genetic traits for altruism to survive, but when altruists lavish their resources on non-altruists at the expense of their own kind, the altruists tend to die out and the others tend to increase. An extreme example is a soldier losing his life trying to help a fellow soldier. This example raises the question of how altruistic genes can be passed on if this soldier dies without having any children. [14]

Within sociobiology, a social behavior is first explained as a sociobiological hypothesis by finding an evolutionarily stable strategy that matches the observed behavior. Stability of a strategy can be difficult to prove, but usually, it will predict gene frequencies. The hypothesis can be supported by establishing a correlation between the gene frequencies predicted by the strategy, and those expressed in a population.

Altruism between social insects and littermates has been explained in such a way. Altruistic behavior, behavior that increases the reproductive fitness of others at the apparent expense of the altruist, in some animals has been correlated to the degree of genome shared between altruistic individuals. A quantitative description of infanticide by male harem-mating animals when the alpha male is displaced as well as rodent female infanticide and fetal resorption are active areas of study. In general, females with more bearing opportunities may value offspring less, and may also arrange bearing opportunities to maximize the food and protection from mates.

An important concept in sociobiology is that temperament traits exist in an ecological balance. Just as an expansion of a sheep population might encourage the expansion of a wolf population, an expansion of altruistic traits within a gene pool may also encourage increasing numbers of individuals with dependent traits.

Studies of human behavior genetics have generally found behavioral traits such as creativity, extroversion, aggressiveness, and IQ have high heritability. The researchers who carry out those studies are careful to point out that heritability does not constrain the influence that environmental or cultural factors may have on those traits. [15] [16]

Criminality is actively under study, but extremely controversial. [ citation needed ] Various theorists have argued that in some environments criminal behavior might be adaptive. [17] The evolutionary neuroandrogenic (ENA) theory, by sociologist/criminologist Lee Ellis, posits that female sexual selection have led to increased competitive behavior among men, leading to criminality in some cases. In another theory, Mark van Vugt argues that a history of intergroup conflict for resources between men have led to differences in violence and aggression between men and women. [18] The novelist Elias Canetti also has noted applications of sociobiological theory to cultural practices such as slavery and autocracy. [19]

Genetic mouse mutants illustrate the power that genes exert on behaviour. For example, the transcription factor FEV (aka Pet1), through its role in maintaining the serotonergic system in the brain, is required for normal aggressive and anxiety-like behavior. [20] Thus, when FEV is genetically deleted from the mouse genome, male mice will instantly attack other males, whereas their wild-type counterparts take significantly longer to initiate violent behaviour. In addition, FEV has been shown to be required for correct maternal behaviour in mice, such that offspring of mothers without the FEV factor do not survive unless cross-fostered to other wild-type female mice. [21]

A genetic basis for instinctive behavioural traits among non-human species, such as in the above example, is commonly accepted among many biologists however, attempting to use a genetic basis to explain complex behaviours in human societies has remained extremely controversial. [22] [23]

Steven Pinker argues that critics have been overly swayed by politics and a fear of biological determinism, [a] accusing among others Stephen Jay Gould and Richard Lewontin of being "radical scientists", whose stance on human nature is influenced by politics rather than science, [25] while Lewontin, Steven Rose and Leon Kamin, who drew a distinction between the politics and history of an idea and its scientific validity, [26] argue that sociobiology fails on scientific grounds. Gould grouped sociobiology with eugenics, criticizing both in his book The Mismeasure of Man. [27]

Noam Chomsky has expressed views on sociobiology on several occasions. During a 1976 meeting of the Sociobiology Study Group, as reported by Ullica Segerstråle, Chomsky argued for the importance of a sociobiologically informed notion of human nature. [28] Chomsky argued that human beings are biological organisms and ought to be studied as such, with his criticism of the "blank slate" doctrine in the social sciences (which would inspire a great deal of Steven Pinker's and others' work in evolutionary psychology), in his 1975 Reflections on Language. [29] Chomsky further hinted at the possible reconciliation of his anarchist political views and sociobiology in a discussion of Peter Kropotkin's Mutual Aid: A Factor of Evolution, which focused more on altruism than aggression, suggesting that anarchist societies were feasible because of an innate human tendency to cooperate. [30]

Wilson has claimed that he had never meant to imply what ought to be, only what is the case. However, some critics have argued that the language of sociobiology readily slips from "is" to "ought", [26] an instance of the naturalistic fallacy. Pinker has argued that opposition to stances considered anti-social, such as ethnic nepotism, is based on moral assumptions, meaning that such opposition is not falsifiable by scientific advances. [31] The history of this debate, and others related to it, are covered in detail by Cronin (1993), Segerstråle (2000), and Alcock (2001).

Animal Communication and Living in Groups

Animals communicate using signals, which can be chemical (pheromones), aural (sound), visual (courtship displays), or tactile (touch).

Learning Objectives

Differentiate among the ways in which animals communicate

Key Takeaways

Key Points

  • Animals need to communicate with one another in order to successfully mate, which usually involves one animal signaling another the energy-intensive behaviors or displays associated with mating are called mating rituals.
  • Animal signaling is not the same as the communication we associate with language, which has been observed only in humans, but may also occur in some non-human primates and cetaceans.
  • Animal communication by stimuli known as signals may be instinctual, learned, or a combination of both.

Key Terms

  • pheromone: a chemical secreted by an animal that affects the development or behavior of other members of the same species, functioning often as a means of attracting a member of the opposite sex

Innate behaviors: living in groups

Not all animals live in groups, but even those that live relatively-solitary lives (with the exception of those that can reproduce asexually) must mate. Mating usually involves one animal signaling another so as to communicate the desire to mate. There are several types of energy-intensive behaviors or displays associated with mating called mating rituals. Other behaviors found in populations that live in groups are described in terms of which animal benefits from the behavior. In selfish behavior, only the animal in question benefits in altruistic behavior, one animal’s actions benefit another animal cooperative behavior occurs when both animals benefit. All of these behaviors involve some sort of communication between population members.

Communication within a species

Animals communicate with each other using stimuli known as signals. These signals are chemical ( pheromones ), aural (sound), visual (courtship and aggressive displays), or tactile (touch). These types of communication may be instinctual, learned, or a combination of both. These are not the same as the communication we associate with language, which has been observed only in humans and, perhaps, in some species of primates and cetaceans.

A pheromone is a secreted, chemical signal used to obtain a response from another individual of the same species. The purpose of pheromones is to elicit a specific behavior from the receiving individual. Pheromones are especially common among social insects, but they are used by many animal species to attract the opposite sex, to sound alarms, to mark food trails, and to elicit other, more-complex behaviors. Even humans are thought to respond to certain pheromones called axillary steroids. These chemicals influence human perception of other people. In one study, they were responsible for a group of women synchronizing their menstrual cycles. The role of pheromones in human-to-human communication is still somewhat controversial and continues to be researched.

Songs are an example of an aural signal: one that needs to be heard by the recipient. Perhaps the best known of these are songs of birds, which identify the species and are used to attract mates. Other well-known songs are those of whales, which are of such low frequency that they can travel long distances underwater. Dolphins communicate with each other using a wide variety of vocalizations. Male crickets make chirping sounds using a specialized organ to attract a mate, repel other males, and to announce a successful mating.

Courtship displays are a series of ritualized visual behaviors (signals) designed to attract and convince a member of the opposite sex to mate. These displays are ubiquitous in the animal kingdom. They often involve a series of steps, including an initial display by one member followed by a response from the other. If at any point the display is performed incorrectly or a proper response is not given, the mating ritual is abandoned and the mating attempt will be unsuccessful.

Courtship displays: A male peacock’s extravagant, eye-spotted tail is used in courtship displays to attract a mate.

Aggressive displays are also common in the animal kingdom. As, for example, when a dog bares its teeth to get another dog to back down. Presumably, these displays communicate not only the willingness of the animal to fight, but also its fighting ability. Although these displays do signal aggression on the part of the sender, it is thought that they are actually a mechanism to reduce the amount of fighting that occurs between members of the same species: they allow individuals to assess the fighting ability of their opponent and thus decide whether it is “worth the fight.”

Distraction displays are seen in birds and some fish. They are designed to attract a predator away from the nest that contains their young. This is an example of an altruistic behavior: it benefits the young more than the individual performing the display, which is putting itself at risk by doing so.

Many animals, especially primates, communicate with other members in the group through touch. Activities such as grooming, touching the shoulder or root of the tail, embracing, lip contact, and greeting ceremonies have all been observed in the Indian langur, an Old World monkey. Similar behaviors are found in other primates, especially in the great apes.

15.11.1: Innate Behavior - Biology

Ethology is the zoological study of animal behavior. The word "ethology", derived from the Greek "ethos," meaning "character", and "logia," meaning "the study of", was coined to describe a sub-topic of zoology - the scientific study of animal behavior. American biologist William Morton Wheeler, who specialized in the study of ants (a myrmecologist), first popularized the term in 1902.

More specifically, ethologists are primarily interested in behaviors that are genetically ingrained within animals - their instinctual behavior - rather than any learned behavior animals may obtain from their parents or other creatures. This is how ethologists differ from "animal behaviorists." Animal behaviorists are primarily interested in studying learned behaviors. Additionally, animal behaviorists are generally trained in psychology, while ethologists are considered zoologists.

The behavioral "programs" that animals inherit through their parents are affected by the process of natural selection and can change over time as animals evolve and change to better fit their environment. Therefore, these innate behaviors can be traced back through time providing an evolutionary history for the behavior.

Researchers study these behavioral changes in other primates, such as chimps, to determine how they may relate to the biological basis of human behavior. This type of study, called phylogenetics is the study of evolutionary relatedness among groups of organisms.

The origins of ethology date back to Charles Darwin's work with the so-called "expressive movements" of man and animals. He was the first naturalist to utilize the comparative phylogenetic method in the study of animal behavior. His book on the subject, The Expression of the Emotions in Man and Animal, influenced many future ethologists.

Early ethologists Julian Huxley and Oskar Heinroth specialized in studying animal behaviors that are considered instinctive, or "natural." These are behaviors that are found to occur naturally (as opposed to learned) in all members of a given species. Huxley and Heinroth developed a tool called an "ethogram" which they used at the beginning of each behavioral study of a new species. The ethogram is a detailed description of the main types of natural behavior noted along with the frequencies of the behavior's occurrence.

The modern history of ethology began in the 1930s with the work of biologists Nikolaas Tinbergen, Konrad Lorenz, and Karl von Frisch. These three men shared the 1973 Nobel Prize in Physiology or Medicine and are generally accepted as the "fathers of ethology."

Lorenz is known for his identification of "fixed action patterns," or FAPs. An FAP is an action patter that is an instinctive response that occurs reliably when an animal is exposed to certain identifiable stimuli (sometimes called sign or releasing stimuli).

Once FAPs are documented, they can be compared between different species, making it simpler to identify the similarities and differences between behavior that may then be more easily compared with the similarities and differences in animal morphology. Work by Karl von Frisch built on FAPs in his study of the "dance language" used by bees as a communicative device.

Another well-known ethologist, Irenus Eibl-Eibesfeldt, successfully applied ethological methods such as FAPs to human behavior. Eibl-Eibesfeldt's best known work was the study and recording of communication between humans using a side-viewing camera that allowed him to study his subjects without them knowing they were being observed. He then compared FAPs, like gestures and body language, across various cultures and was able to identify many behavior patterns in humans that are considered to be innate rather than learned.

A now well-recognized and respected scientific discipline, ethology is now studied by many biologists, primatologists, zoologists, and anthropologists as well as by veternarians and physicians! In fact, most ethology researchers obtain advanced degrees in one of these science specialties before beginning their studies in ethology.

Following is a listing of many of the scientists, past and present, who have made notable contributions to the study of ethology:

- Robert Ardrey
- John C Angel
- George Barlow
- Adrian Simpson
- Patrick Bateson
- John Bowlby
- Donald Broom
- Dorothy Cheney
- Raymond Coppinger
- John H. Crook
- Marian Stamp Dawkins
- Richard Dawkins
- Irenäus Eibl-Eibesfeldt
- John Endler
- Jean-Henri Fabre
- John Fentress
- Dian Fossey
- Karl von Frisch
- Douglas P. Fry
- Jane Goodall
- James L. Gould
- Judith Hand
- Clarence Ellis Harbison
- Heini Hediger
- Oskar Heinroth
- Robert Hinde
- Bernard Hollander
- Sarah Hrdy
- Julian Huxley
- Lynne Isbell[11]
- Julian Jaynes
- Alex Kacelnik
- Erich Klinghammer
- Peter Klopfer
- Otto Koehler
- John Krebs
- Paul Leyhausen
- Konrad Lorenz
- Aubrey Manning
- Eugene Marais
- Patricia McConnell
- Desmond Morris
- Martin Moynihan
- Caitlin O'Connell-Rodwell[12]
- Manny Puig
- Irene Pepperberg
- George Romanes
- Thomas A. Sebeok
- Edward Selous
- Robert Seyfarth
- B. F. Skinner
- Barbara Smuts
- William Homan Thorpe
- Niko Tinbergen
- Jakob von Uexküll
- Frans de Waal
- William Morton Wheeler
- E. O. Wilson
- Amotz Zahavi

Content copyright © 2021 by Deborah Watson-Novacek. All rights reserved.
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Researchers Show How The Brain Turns On Innate Behavior

UCR researchers have made a major leap forward in understanding how the brain programs innate behavior. The discovery could have future applications in engineering new behaviors in animals and intelligent robots.

Innate or "instinctive" behaviors are inborn and do not require learning or prior experience to be performed. Examples include courtship and sexual behaviors, escape and defensive maneuvers, and aggression.

Using the common fruit fly as a model organism, the researchers found through laboratory experiments that the innate behavior is initiated by a "command" hormone that orchestrates activities in discrete groups of peptide neurons in the brain. Peptide neurons are brain cells that release small proteins to communicate with other brain cells and the body.

The researchers report that the command hormone, called ecdysis-triggering hormone or ETH, activates discrete groups of brain peptide neurons in a stepwise manner, making the fruit fly perform a well-defined sequence of behaviors. The researchers propose that similar mechanisms could account for innate behaviors in other animals and even humans.

Study results appear as the cover article in this week's issue of Current Biology.

"To our knowledge, we are the first to describe how a circulating hormone turns on sequential steps of an innate behavior by inducing programmed release of brain chemicals," said Young-Joon Kim, a postgraduate researcher in UCR's Department of Entomology working with Michael Adams, professor of cell biology and neuroscience and professor of entomology, and the first author of the paper. "It is well known that such behaviors -- for example, sexual behavior or those related to aggression, escape or defense -- are programmed in the brain, and all are laid down in the genome. We found that not only do steps involved in innate behavior match exactly with discrete activities of the neurons in the brain but also that specific groups of peptide neurons are activated at very precise times, leading to each successive step of the behavioral sequence."

In their experiments, which involved state of the art imaging techniques that helped the researchers see activated neurons light up in the fruit fly brain, the researchers specifically focused on arthropods, such as insects. Insects pass through multiple developmental stages during their life history. Each transition requires molting, a process in which a new exoskeleton (or cuticle) is produced and the old is shed. Insects shed the old cuticle by performing an innate behavior consisting of three distinct steps lasting about 100 minutes in total.

First, the researchers described the ecdysis sequence, an innate behavior that insects perform to escape their old cuticle, and showed that the insect initiates behavior shortly after appearance of ETH in the blood. The researchers then demonstrated that injection of the hormone into an animal generates the same behavior. To investigate mechanisms underlying this hormone-induced behavior, they used real-time imaging techniques to reveal activities in discrete sets of peptide neurons at very precise times, which corresponded to each successive step of the behavioral sequence. The researchers confirmed the results by showing that behavioral steps disappear or are altered upon killing certain groups of brain neurons with genetic tools.

"Our results apply not only to insects they also may provide insights into how, in general, the mammalian brain programs behavior, and how it and the body schedule events," said Adams, who led the research team. "By understanding how innate behavior is wired in the brain, it becomes possible to manipulate behavior -- change its order, delay it or even eliminate it altogether -- all of which opens up ethical questions as to whether scientists should, or would want to, engineer behavior in this way in the future."

The fruit fly is a powerful tool and a classic laboratory model for understanding human diseases and genetics because it shares many genes and biochemical pathways with humans.

Besides Kim and Adams, UCR's Dusan Zitnan, C. Giovanni Galizia and Kook-Ho Cho collaborated on the study which was supported by a grant from the National Institutes of Health and a Rotary Foundation Ambassadorial Scholarship to Kim.

Watch the video: Behavior Introduction to Ethology and Innate behavior (September 2022).


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