Chapter 3. Development of Behavior Development is an interactive process in which the genes are turned on and off both in response to environmental

Chapter 3Chapter 3

Development of BehaviorDevelopment of Behavior

Development is an interactive process in Development is an interactive process in which the genes are turned on and off which the genes are turned on and off both in response to environmental change both in response to environmental change and simultaneously creating change.and simultaneously creating change.

This demonstrated by changes in behavior This demonstrated by changes in behavior shown by honeybees over the course of shown by honeybees over the course of their lives.their lives.


Honeybees when they emerge as adults Honeybees when they emerge as adults first work at cleaning cells then as they first work at cleaning cells then as they age they shift to other tasks. age they shift to other tasks.

Eventually at about age 3 weeks they Eventually at about age 3 weeks they begin foraging outside the hive.begin foraging outside the hive.


As the bee goes through these changes in As the bee goes through these changes in behavior it appears that predictable behavior it appears that predictable changes in the genes being actively changes in the genes being actively expressed occur.expressed occur.

Microarray technology makes it possible to Microarray technology makes it possible to scan for activity levels of many genes by scan for activity levels of many genes by detecting mRNA made when genes are detecting mRNA made when genes are turned on.turned on.


Comparisons of arrays of nurse and Comparisons of arrays of nurse and forager bees shows substantial differences forager bees shows substantial differences in genes turned on at each stage.in genes turned on at each stage.

(YN= young nurses, OF = older foragers)


Transition to worker role appears to be strongly Transition to worker role appears to be strongly influenced by level of a hormone called juvenile influenced by level of a hormone called juvenile hormone, which is produced by a gene. hormone, which is produced by a gene.

The juvenile hormone gene turns on apparently The juvenile hormone gene turns on apparently in response to activity of other genes during 1in response to activity of other genes during 1stst three weeks of adulthood , but can also be three weeks of adulthood , but can also be turned on in response to conditions in the hive.turned on in response to conditions in the hive.


If colonies are artificially made up of only young If colonies are artificially made up of only young workers some become foragers much sooner workers some become foragers much sooner and others remain as nurse bees much longer.and others remain as nurse bees much longer.

It may be social encounters that stimulate these It may be social encounters that stimulate these changes.changes.

Lack of encounters with older foragers appears Lack of encounters with older foragers appears to hasten nurse bees transition to forager role. to hasten nurse bees transition to forager role.


Adding numbers of older bees to hives Adding numbers of older bees to hives that contain only young bees reduces the that contain only young bees reduces the number of young bees that become number of young bees that become foragers.foragers.

In contrast, adding more young bees does In contrast, adding more young bees does not slow rate at which young bees become not slow rate at which young bees become foragers.foragers.


Inhibiting agent believed to be a chemical Inhibiting agent believed to be a chemical called ethyl oleate that foragers called ethyl oleate that foragers manufacture and store in their crop. manufacture and store in their crop.

When foragers transfer food to nurse bees When foragers transfer food to nurse bees they transfer the chemical, which slows they transfer the chemical, which slows the nurses transition to foragers. the nurses transition to foragers.


In honeybees, therefore, sequence of In honeybees, therefore, sequence of behavioral changes is determined by behavioral changes is determined by continuous interactions between genes continuous interactions between genes and both chemical and social and both chemical and social environments.environments.

Nature vs Nurture DebateNature vs Nurture Debate

Nature: genetic contribution to behavior.Nature: genetic contribution to behavior.

Nurture: environmental contribution to Nurture: environmental contribution to molding behavior.molding behavior.

There is a false dichotomy in popular There is a false dichotomy in popular discussions in which traits are considered discussions in which traits are considered to be genetically or environmentally to be genetically or environmentally determined.determined.


In reality, all traits are the product of In reality, all traits are the product of

gene-environment interactions.gene-environment interactions.

As we saw in the process of song learning As we saw in the process of song learning there is considerable gene-environment there is considerable gene-environment interaction.interaction.


Environmental or geneticEnvironmental or genetic differences differences among individuals can lead to differences among individuals can lead to differences in development and finally differences in in development and finally differences in behavior.behavior.

What causes individuals to develop What causes individuals to develop differently?differently?

Environmental differences and behavioral Environmental differences and behavioral differences.differences.

Many behavioral differences result from differences Many behavioral differences result from differences in experience.in experience.

For example, marsh tits fed whole sunflower seeds, For example, marsh tits fed whole sunflower seeds, which they can hide and later retrieve, develop a which they can hide and later retrieve, develop a larger hippocampus in their brain than birds fed larger hippocampus in their brain than birds fed only powdered sunflower seeds. Practice of storing only powdered sunflower seeds. Practice of storing and retrieving seeds alters brain development. and retrieving seeds alters brain development.

Learning of nestmates in Polistes Learning of nestmates in Polistes waspswasps

Polistes wasps learn to identify the smell Polistes wasps learn to identify the smell of their natal nest and tolerate individuals of their natal nest and tolerate individuals that smell like the nest (whether or not that smell like the nest (whether or not they are relatives).they are relatives).

Individuals with a different smell are Individuals with a different smell are attacked. Differences in how wasps attacked. Differences in how wasps behave towards each other thus are based behave towards each other thus are based on the smells they learned when young. on the smells they learned when young.

Similar discrimination between individuals Similar discrimination between individuals reared together versus apart has been reared together versus apart has been shown in Belding’s Ground Squirrels.shown in Belding’s Ground Squirrels.

Non-relatives reared together act nicely Non-relatives reared together act nicely towards each other. However, relatives towards each other. However, relatives reared apart also act nicely towards each reared apart also act nicely towards each other.other.

Ground squirrels apparently learn what Ground squirrels apparently learn what theythey themselves smell like and use this information to themselves smell like and use this information to evaluate their relatedness to other individuals.evaluate their relatedness to other individuals.

Trials in which squirrels provided with cubes Trials in which squirrels provided with cubes smeared with dorsal gland secretions of other smeared with dorsal gland secretions of other individuals respond more strongly to those of individuals respond more strongly to those of non-relatives and discriminate between different non-relatives and discriminate between different degrees of relatedness.degrees of relatedness.

Genetic differences and Genetic differences and behavioral differencesbehavioral differences

Breeding experiments can show whether Breeding experiments can show whether behavioral differences between behavioral differences between populations have a genetic basis. populations have a genetic basis.

Funnel Web SpidersFunnel Web Spiders

Spiders in different habitats differ in their Spiders in different habitats differ in their speed of reaction to food being caught in speed of reaction to food being caught in their webs.their webs.

Streamside spiders react slowly.Streamside spiders react slowly. Desert grassland spiders react quickly.Desert grassland spiders react quickly. Is difference largely environmental or Is difference largely environmental or

genetic?genetic?

Funnel Web SpidersFunnel Web Spiders

Spiders bred in lab.Spiders bred in lab. Offspring of both populations kept equally Offspring of both populations kept equally

well fed. Then offered food.well fed. Then offered food. Desert spider reaction time: 3s.Desert spider reaction time: 3s. Streamside spider reaction time: 60s.Streamside spider reaction time: 60s. Most of the difference in behavior Most of the difference in behavior

apparently due to genetic differences apparently due to genetic differences between populations.between populations.

Migratory behavior of European Blackcaps


Blackcaps are small European warblers, Blackcaps are small European warblers, most of which migrate to Africa to winter. most of which migrate to Africa to winter. However, some spend the winter in However, some spend the winter in Britain.Britain.

What causes this difference in behavior?What causes this difference in behavior?


Peter Berthold caught wintering blackcaps Peter Berthold caught wintering blackcaps in Britain.in Britain.

He then bred these birds in central He then bred these birds in central Germany in outdoor cages.Germany in outdoor cages.


In fall Berthold looked at migratory In fall Berthold looked at migratory direction selected by birds.direction selected by birds.

Used an Emlen funnel to record Used an Emlen funnel to record orientation.orientation.

Emlen Funnel

Blackcaps oriented in a westerly direction.

Conclusion? British birds from where?


Based on orientation birds not from Based on orientation birds not from Scandinavia or northern Britain.Scandinavia or northern Britain.

Birds probably from due east of Britain Birds probably from due east of Britain Belgium or Germany.Belgium or Germany.


Could environmental influences be Could environmental influences be responsible? responsible?

Perhaps, just being in Germany causes Perhaps, just being in Germany causes westward orientation.westward orientation.


To check birds from SW Germany were To check birds from SW Germany were bred in captivity.bred in captivity.

Migratory orientation was checked.Migratory orientation was checked.

SW German birds oriented southwest.


Differences in orientation between Differences in orientation between populations largely determined by genetic populations largely determined by genetic differences.differences.

Southwest German birds migrate SW Southwest German birds migrate SW traveling west of the Mediterranean via traveling west of the Mediterranean via Spain.Spain.


Andreas Helbig has shown that Blackcaps Andreas Helbig has shown that Blackcaps from Austria orient southeast.from Austria orient southeast.

They travel east of the Mediterranean via They travel east of the Mediterranean via Turkey and Israel.Turkey and Israel.


Helbig crossed birds from Austria with Helbig crossed birds from Austria with birds from southwest Germany.birds from southwest Germany.

What direction did they orient?What direction did they orient?

Mean orientation of offspring south.

Inner ring Adults.

Outer ring Offspring.


Due south is a poor choice. Requires bird Due south is a poor choice. Requires bird to cross the Alps and the make a long sea to cross the Alps and the make a long sea crossing over the Mediterranean.crossing over the Mediterranean.

Single gene effects on Single gene effects on developmentdevelopment

In theory a single gene difference could be In theory a single gene difference could be responsible for difference in orientation on responsible for difference in orientation on different Blackcap populations.different Blackcap populations.

Note a single gene does not encode Note a single gene does not encode migratory choices, but a change in a single migratory choices, but a change in a single gene can result in many gene-environment gene can result in many gene-environment effects and ultimately produce a large effects and ultimately produce a large behavioral difference. behavioral difference.

Rovers move a lot when feeding.Sitters move very little.

Sitter

Rover

Two strains of Drosophila differ in larval foraging behavior.

Rover/sitter behavior in Rover/sitter behavior in DrosophilaDrosophila

When the two strains were crossed in the When the two strains were crossed in the F1 generation all of the larvae were F1 generation all of the larvae were rovers.rovers.

A cross of members of the F1 generation A cross of members of the F1 generation produced a 3:1 ratio of rovers to sitters.produced a 3:1 ratio of rovers to sitters.


One gene appears to be responsible for One gene appears to be responsible for difference between phenotypes.difference between phenotypes.

The rover allele is dominant and the sitter The rover allele is dominant and the sitter allele is recessive. Gene that affects allele is recessive. Gene that affects rover/sitter behavior affects the olfactory rover/sitter behavior affects the olfactory system and may affect fly’s ability to sense system and may affect fly’s ability to sense its environment.its environment.


Many other single gene effects in Many other single gene effects in Drosophila.Drosophila.

E.g. E.g. StuckStuck: males don’t dismount after : males don’t dismount after normal 20 minutes of copulation.normal 20 minutes of copulation.

Coitus interruptusCoitus interruptus: male copulates for only : male copulates for only 10 minutes.10 minutes.

Single gene examples from lab Single gene examples from lab micemice

Mice homozygous for allele for defective form of calmodulin kinase have poor learning ability.

Single gene examples from lab Single gene examples from lab micemice

Mouse placed in water-filled container.Mouse placed in water-filled container. Submerged platform available for rest.Submerged platform available for rest. Normal and mutant mice tested with Normal and mutant mice tested with

platform in random locations and original platform in random locations and original testing position.testing position.

Time to find platform measured.Time to find platform measured.

When platform kept in same location as in training trials wild-type mice found platform much faster than mutant mice, but not if position of platform was randomized.

fosBfosB gene gene

In normal mice sniffing and touching pups In normal mice sniffing and touching pups causes changes in female’s brain that causes changes in female’s brain that prompt her to care for pups. prompt her to care for pups.

Mice homozygous for inactive Mice homozygous for inactive fosBfosB gene gene ignore their pups.ignore their pups.

Funtional Funtional fosBfosB gene usually activated in gene usually activated in hypothalamus by smell of newborn pups.hypothalamus by smell of newborn pups.

Pups

Female with active fosB

Female with inactive fosB

OxtOxt gene gene

Mice missing Oxt gene cannot produce oxytocin.

Mutant male mice cannot remember scent of females they recently interacted with.

A gene “for”A gene “for”

Remember that one gene Remember that one gene does not codedoes not code for a behavior.for a behavior.

One gene codes for one enzyme.One gene codes for one enzyme.

Bit a change in one enzyme can alter Bit a change in one enzyme can alter numerous gene-environment interactions numerous gene-environment interactions and produce a detectable difference in the and produce a detectable difference in the phenotype.phenotype.

A gene “for”A gene “for”

The phrase “a gene for” some behavior is The phrase “a gene for” some behavior is shorthand for: a shorthand for: a changechange in the gene leads in the gene leads to a to a changechange in behavior. in behavior.

All else being equal,All else being equal, a change in a gene a change in a gene can result in a detectable change in a can result in a detectable change in a phenotype.phenotype.

Evolution and behavioral Evolution and behavioral developmentdevelopment

Garter Snake

In California, coastal and inland populations of garter snakes differ in diet.

Coastal garter snakes feed on banana slugs.

Inland populations eat other foods e.g. fish and frogs.

Is there a genetic basis to the behavioral Is there a genetic basis to the behavioral differences in diet preference?differences in diet preference?

Steve Arnold studied populations to see ifthere were genetic differences between them.

Brought pregnant females into lab and reared babies in isolation.

Offered slug pieces to snakes.

Inland snakes usually ignored slugs, coastalsnakes usually ate it.

Then tested newborn snakes on response toodors.

Offered snakes flavored cotton swabs, counted number of tongue flicks made.

Coastal individuals responded much more strongly to slug odor.

Arnold carried out heritability studies.

Found little variation within either population.

Preference for slugs within a population largely fixed.

Crosses between populations produced individuals with wide variation in response to slugs.

Suggests differences between populations have strong genetic component.

What is evolutionary basis for difference between populations?Advantage to slug eating on coast is

obvious.

Rare gene for eating slugs would spread rapidly.

Artificial selection and Artificial selection and behavioral evolutionbehavioral evolution

Nest building in mice.Nest building in mice.

In starting population mice used 13-18 In starting population mice used 13-18 grams of cotton to line their nests.grams of cotton to line their nests.

Carol Lynch selected for “high”, “low” and Carol Lynch selected for “high”, “low” and “control” groups of mice.“control” groups of mice.

After 15 generations amounts of cotton After 15 generations amounts of cotton used by mice were: used by mice were: Controls 15g same as original population.Controls 15g same as original population. High 40gHigh 40g Low 5gLow 5g

Other examples of Artificial Other examples of Artificial SelectionSelection

William Cade has selectively bred crickets William Cade has selectively bred crickets to sing rarely or almost continuously. to sing rarely or almost continuously.

In only two generations of artificial In only two generations of artificial selection Pulido et al. showed that the selection Pulido et al. showed that the timing of migration in European Blackcaps timing of migration in European Blackcaps could be delayed more than a week.could be delayed more than a week.

Artificial SelectionArtificial Selection

Artificial selection experiments show that Artificial selection experiments show that (i) behavior is subject to selection and (ii) (i) behavior is subject to selection and (ii) populations contain sufficient genetic populations contain sufficient genetic variability to evolve rapidly. variability to evolve rapidly.

Adaptability of behavioral Adaptability of behavioral developmentdevelopment

As we have seen the development of As we have seen the development of behavior such as singing can be strongly behavior such as singing can be strongly influenced by environmental effects.influenced by environmental effects.

It is important for development of behavior It is important for development of behavior to be resilient to disturbance so that to be resilient to disturbance so that normal behavior can develop as often as normal behavior can develop as often as possible. possible.

Process of Process of developmental homeostasisdevelopmental homeostasis reduces effects of disturbance.reduces effects of disturbance.


Harlow’s “experiments” with Rhesus Harlow’s “experiments” with Rhesus monkeys showed that rhesus monkeys monkeys showed that rhesus monkeys entirely derived of contact with mothers entirely derived of contact with mothers and “reared” by artificial surrogates gained and “reared” by artificial surrogates gained weight and grew normally but behaviorally weight and grew normally but behaviorally developed abnormally (BIG surprise!) and developed abnormally (BIG surprise!) and were terrified of other monkeys if exposed were terrified of other monkeys if exposed to them.to them.


However, monkeys given even 15 minutes However, monkeys given even 15 minutes contact a day with other young monkeys contact a day with other young monkeys developed essentially normally.developed essentially normally.


As adults, these monkeys interacted As adults, these monkeys interacted normally with others unlike those normally with others unlike those individuals which had no social contacts individuals which had no social contacts as infants, which were withdrawn or very as infants, which were withdrawn or very aggressive.aggressive.

Read Dawkins chapters 4 and 5 for next Read Dawkins chapters 4 and 5 for next Friday.Friday.

First exam is Wednesday February 22First exam is Wednesday February 22ndnd..

Developmental homeostasis in Developmental homeostasis in human embryonic developmenthuman embryonic development

We saw in studies of songbirds that adult We saw in studies of songbirds that adult ability to learn and sing complex songs ability to learn and sing complex songs was affected by food deprivation during was affected by food deprivation during period of rapid nestling growth.period of rapid nestling growth.

In humans food deprivation of the mother In humans food deprivation of the mother during pregnancy appears not to have during pregnancy appears not to have major effects on the fetus’ intelligence. major effects on the fetus’ intelligence.

Developmental homeostasis in Developmental homeostasis in human embryonic developmenthuman embryonic development

Studies of children whose mothers were Studies of children whose mothers were food deprived during the Nazi transport food deprived during the Nazi transport embargo of Holland in late WWII showed embargo of Holland in late WWII showed that these children had comparable that these children had comparable intelligence scores and rates of mental intelligence scores and rates of mental retardation as children whose mothers retardation as children whose mothers were not food deprived.were not food deprived.

Symmetry and attractivenessSymmetry and attractiveness

Many organisms are influenced by how Many organisms are influenced by how symmetrical other individuals are when symmetrical other individuals are when making mate choices.making mate choices.

Asymmetries are believed to be caused by Asymmetries are believed to be caused by problems in development and symmetry problems in development and symmetry thus signals an ability to overcome thus signals an ability to overcome developmental challenges. developmental challenges.

Symmetry and attractivenessSymmetry and attractiveness

There is some evidence that humans There is some evidence that humans include symmetry in their ratings of an include symmetry in their ratings of an individuals’ attractiveness, but data are not individuals’ attractiveness, but data are not conclusive and there is considerable conclusive and there is considerable debate.debate.

Female brush-legged wolf spiders, Female brush-legged wolf spiders, however, are significantly more likely to however, are significantly more likely to mate with males whose foreleg hair tufts mate with males whose foreleg hair tufts are symmetrical than those who are not.are symmetrical than those who are not.

Study was carried out using video images Study was carried out using video images of spiders that were identical apart from of spiders that were identical apart from the digitally manipulated foreleg tufts.the digitally manipulated foreleg tufts.

PolyphenismPolyphenism

In many species multiple alternative In many species multiple alternative phenotypes occur in the same species (i.e. phenotypes occur in the same species (i.e. distinctly different body types occur). distinctly different body types occur).

These different phenotypes arise as a These different phenotypes arise as a result of environmental effects. The result of environmental effects. The environmental influence sends the environmental influence sends the developing organism down one or another developing organism down one or another distinct developmental pathway.distinct developmental pathway.

Developmental flexibility in Tiger Developmental flexibility in Tiger SalamndersSalamnders

Larvae live in ephemeral ponds.Larvae live in ephemeral ponds.

Most follow “normal” development and eat Most follow “normal” development and eat small invertebrates.small invertebrates.

But some become cannibals (bigger with But some become cannibals (bigger with larger teeth) and eat smaller salamanders.larger teeth) and eat smaller salamanders.

Normal formNormal form CannibalCannibal

What factors affect decision to What factors affect decision to become a cannibal?become a cannibal?

Ideas?Ideas?

What factors affect decision to What factors affect decision to become a cannibal?become a cannibal?

Relatedness of cannibal to others in pool.Relatedness of cannibal to others in pool. Density of salamandersDensity of salamanders Size distribution of salamandersSize distribution of salamanders

A salamander surrounded by lots of non-A salamander surrounded by lots of non-kin can benefit by becoming a cannibal.kin can benefit by becoming a cannibal.

By growing faster it can escape from the By growing faster it can escape from the pond sooner.pond sooner.

Developmental flexibility allows Developmental flexibility allows salamander to adjust its development if salamander to adjust its development if conditions are suitable, but not otherwise.conditions are suitable, but not otherwise.

Behavioral flexibilityBehavioral flexibility

Many animals choose among different Many animals choose among different behavioral phenotypes depending on behavioral phenotypes depending on environmental circumstances.environmental circumstances.

For example, in many fish males adopt different For example, in many fish males adopt different roles depending on their size and status. Large roles depending on their size and status. Large males defend territories but smaller satellite males defend territories but smaller satellite males act as sneakers darting in and releasing males act as sneakers darting in and releasing sperm whenever the dominant male mates with sperm whenever the dominant male mates with a female.a female.

Behavioral flexibility in Behavioral flexibility in HaplochromisHaplochromis burtoniburtoni

In cichlid fish In cichlid fish HaplochromisHaplochromis burtoniburtoni territorial males are brightly colored and territorial males are brightly colored and satellite males are dull.satellite males are dull.

Behavior is related to brain structure.Behavior is related to brain structure.

TerritorialTerritorialmalemale

SatelliteSatellitemalemale


GnRH (gonadotropin releasing hormone) GnRH (gonadotropin releasing hormone)

neurons in hypothalamus are 6-8 times neurons in hypothalamus are 6-8 times

larger in territorial males than in satellites.larger in territorial males than in satellites.

GnRH neurons stimulate testes GnRH neurons stimulate testes

development and aggressive behavior.development and aggressive behavior.


Interestingly, GnRH size is Interestingly, GnRH size is variablevariable..

If male loses territory his neurons shrink If male loses territory his neurons shrink

and he becomes dull colored.and he becomes dull colored.

If territory opens up, male enlarges If territory opens up, male enlarges neurons, switches to aggressive territorial neurons, switches to aggressive territorial mode mode


Unpredictable social environment favors

flexibility in Haplochromis.

Neuronal flexibility allows males to adopt

best strategy for conditions.

LearningLearning

Learning major element in behavioralLearning major element in behavioralflexibility. Ability to make use of flexibility. Ability to make use of experience in adjusting behavior can experience in adjusting behavior can be selectively very advantageous. be selectively very advantageous.

Learning in Australian Thynnine Learning in Australian Thynnine waspswasps

Males search for females based on Males search for females based on pheromones they produce.pheromones they produce.

Orchids attract males using a similar Orchids attract males using a similar scent.scent.

Orchid mimics female wasps appearance Orchid mimics female wasps appearance too. When male lands and attempts to too. When male lands and attempts to mate he gets a surprise. mate he gets a surprise.

Male tries to mate with “female wasp” Male tries to mate with “female wasp” on orchid, instead acquires a pollen sac. on orchid, instead acquires a pollen sac.

Female wasp Fake wasp

Pollinia onPollinia onwasp’s backwasp’s back

Wasps don’t learn to avoid orchids in Wasps don’t learn to avoid orchids in general. general.

But, do learn to avoid orchids they have But, do learn to avoid orchids they have visited before.visited before.

Learning in Australian Thynnine Learning in Australian Thynnine waspswasps

What do wasps learn?What do wasps learn?

Orchid’s location or orchid’s scent?Orchid’s location or orchid’s scent?

Speculation: If wasps could learn scent Speculation: If wasps could learn scent differences how plants benefit from having differences how plants benefit from having wasps revisit them?wasps revisit them?

Costs and benefits of learningCosts and benefits of learning

For learning and flexible behavior to For learning and flexible behavior to spread by natural selection, benefits must spread by natural selection, benefits must exceed costs.exceed costs.

Benefits are the ability to exploit the Benefits are the ability to exploit the environment more effectively.environment more effectively.

What are the costs?What are the costs?

Costs and benefits of learningCosts and benefits of learning

Costs: Major cost is additional energy Costs: Major cost is additional energy required to make/maintain neuronal required to make/maintain neuronal tissue.tissue.

Example of cost:Example of cost:

West coast marsh wrens sing more songs West coast marsh wrens sing more songs (100) than east coast marsh wrens (40).(100) than east coast marsh wrens (40).

Song system in brain weighs 25% more Song system in brain weighs 25% more in west coast birds.in west coast birds.

Costs of large brain in humansCosts of large brain in humans

In humans: Brain 2% of body weight.In humans: Brain 2% of body weight.

But requires 15% of body’s oxygen and But requires 15% of body’s oxygen and 20% of energy.20% of energy.

Other costs to large brains in humans?Other costs to large brains in humans?

Costs of large brain in humansCosts of large brain in humans

Difficulty in giving birth.Difficulty in giving birth.

Behavioral flexibility expensive.

Should only evolve when benefit outweighs cost.

Clark’s Nutcracker seed-storing specialist.Clark’s Nutcracker seed-storing specialist.

Much better at remembering Much better at remembering wherewhere Something is located than other crows.Something is located than other crows.

Not better at remembering colors, a non-Not better at remembering colors, a non-spatial task. Memory skills determined spatial task. Memory skills determined by bird’s needs.by bird’s needs.

Intraspecific variability in Intraspecific variability in learninglearning

Behavioral flexibility does not only differ Behavioral flexibility does not only differ between species.between species.

In species where males and females In species where males and females experience different selection pressures, experience different selection pressures, differences in learning ability occur. differences in learning ability occur.

Spatial learning in volesSpatial learning in voles

Male meadow voles are polygynous. Male meadow voles are polygynous. Their home ranges are 4X larger than Their home ranges are 4X larger than those of females.those of females.

Prairie voles are monogamous. Males Prairie voles are monogamous. Males and females have same size home rangesand females have same size home ranges


Spatial learning abilities of voles was Spatial learning abilities of voles was tested in mazes.tested in mazes.

Male meadow voles made significantly Male meadow voles made significantly fewer mistakes than female meadow fewer mistakes than female meadow voles, but there was no difference voles, but there was no difference between the sexes in the performance of between the sexes in the performance of male and female prairie voles.male and female prairie voles.


Male meadow voles have a large Male meadow voles have a large hippocampus than females and this area hippocampus than females and this area in the brain processes spatial information.in the brain processes spatial information.

However, the enlarged hippocampus only However, the enlarged hippocampus only develops during the breeding season.develops during the breeding season.

Spatial learning in cowbirdsSpatial learning in cowbirds

Female cowbirds parasitize other birds Female cowbirds parasitize other birds nests. They need to be able to remember nests. They need to be able to remember nest locations and monitor them over time.nest locations and monitor them over time.

Female cowbirds have a larger Female cowbirds have a larger hippocampus than males. No difference hippocampus than males. No difference between sexes in related, but non-between sexes in related, but non-parasitic grackles and red-winged parasitic grackles and red-winged blackbirds.blackbirds.

Operant conditioningOperant conditioning

Spatial learning not only behavior that has Spatial learning not only behavior that has clearly been shaped by selection.clearly been shaped by selection.

In operant conditioning (or trial and error In operant conditioning (or trial and error learning) an animal learns to associate an learning) an animal learns to associate an action with its consequences.action with its consequences.

E.g. a rat pushes a lever and gets a food E.g. a rat pushes a lever and gets a food pellet.pellet.

Operant conditioningOperant conditioning

Usually a behavior and its consequences Usually a behavior and its consequences must be closely linked in time for must be closely linked in time for conditioning to occur.conditioning to occur.

However, in rats tasting novel foods However, in rats tasting novel foods nausea that occurs several hours after nausea that occurs several hours after eating a food will be associated with that eating a food will be associated with that food, which in future will be avoided.food, which in future will be avoided.

Another example of operant conditioning is Another example of operant conditioning is that predators learn to recognize noxious that predators learn to recognize noxious prey after tasting them.prey after tasting them.

How does warning How does warning

coloration benefit coloration benefit

animal that is tasted animal that is tasted

if it is killed?if it is killed?

Does operant conditioning occur in humans?

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Chapter 3. Development of Behavior Development is an interactive process in which the genes are turned on and off both in response to environmental