Why Animals LearnWithin-Species Studies and the Evolution of

Learning

Garcia’s Rats: Tested response to “bright-noisy” water or “tasty” water and a negative stimuli: radiation, a toxin, immediate shock, or delayed shock.

Rats easily associated X-ray and toxin treatments with tasty water and immediate shock or delayed shock with bright-noisy water, but not vice versa. Why?

-Natural selection favored ability to pair flavor with internal discomfort

- Natural selection favored ability to pair visual cues with peripheral pain

Garcia also showed that learning in animals can occur even after delays of seventy-five minutes, when injections of noxious substances were paired with drinking flavored water.

Optimal Forgetting in Stomatopods: Is it beneficial for a forager to be able to remember the location and amount of food in patches?

Stomatopod crustacean (Gonodactylus bredini)

Male & female G. bredini share a nest cavity for a few days before they breed, & they actively repel all intruders.

Male leaves in search of a new mate shortly after mating.

Males & females remember each other for at least 2 weeks – maybe more.

Why would remembering a mate be beneficial to G. bredini?

Females guard their brood for 4 weeks, after which the young leave the cavity. If the male is aggressive toward the female during that 4 week period they could bring harm to their own young.

Population Comparisons & the Evolution of Learning

Learning, Foraging, & Group Living in Doves:

Animals in groups often find food faster and have more time available for foraging.

Zenaida doves (Zenaida aurita)Do animals that live in groups learn more quickly than territorial individuals?

16 doves from each situation were captured and subjected to an individual test – they had to operate an apparatus that required the birds to pull a metal ring to open a drawer containing food.

Evidence shows that not only do group-living doves learn more quickly, the more pronounced the between-population differences there were as the tasks became more difficult.WH

Y?

1. Animals may have already differed in foraging experience

2. Natural selection may have operated on learning ability across these populations.

Verdict is still out…

Learning and Antipredator Behavior in Sticklebacks: Stickleback fish (Gasterosteus aculeatus) live in both predator rich and predator poor lakes.

Individuals were raised in the lab that came from predator rich and predator poor populations, but were never exposed to predators during their development.

Sticklebacks were trained to associate one side of their tank with food.

No difference was observed regarding individual learning for either population.

Fish were subjected to a simulated attack from a heron predator to examine whether between-population differences emerged in how long it took to learn to avoid the side of the tank associated with the heron (the same side as the food)

1. Minimized the probability that individual experiences differed significantly across the populations

2. Did not find between-population differences in all learning contexts

Importanc

e?

A Model of the Evolution of LearningNatural selection should favor the ability to learn over the genetic transmission of a fixed trait in environments that changes often, but not to often.

When the environment rarely changes information is best passed on genetically.

If the environment is constantly changing there is nothing worth learning because what is learned is completely irrelevant in the next situation.Learning is favored when predictability within the lifetime of an individual is high, but environmental predictability between generations is low.

What Animals LearnLearning Where Home is Located

Fish migration:Evidence supports -

1. Use celestial & magnetic compasses

2. Use drifting currents

3. Physiological change (temp. or O2 change)

4. Learning

Juvenile salmon appear to learn odors of their natal streams – Learning takes place after parr stage (post-larval stage)

Learning About Your Mate

Male and female Mongolian gerbil’s (Meriones unguiculatus) associate odor cues with mates.

Hypothesis: Differences between male and female learning abilities should correlate with differences in parental investment-If both parents involved, learning ability should be strong for both

-If only female is involved, male should be better at learning location of mates

Females valuable resource for males (provide food for offspring). Thus, males are less valuable to females

Japanese quail – no male involvement

Gourami fish – parental invesement is shared

Learning About Familial Relationships

Long-tailed tits (Aegithalos caudatus) breed as soon as they can, but young often fall victim to predation.

The breeders then become helpers at nests of close genetic relatives.

How do the birds know kin?

Playback call experiments indicated the birds’ strong interest in calls made by their relatives.

Did they learn the calls?Cross-fostering the young revealed:

1. Foster siblings had about the same calls as related siblings

2. Biological siblings raised separate had dissimilar calls

3. Songs of foster parents and young were similar; songs of biological parents and their fostered young were dissimilar

Learning About Aggression

Intrinsic factor: Traits that correlate with an animal’s fighting ability

Extrinsic factor: Increased probability of winning an aggressive interaction based on past victories

Blue gourami fish were trained to associate light with either the presence of absence of an male intruder.

The control group saw a light & 6 hours later saw an intruder = no correlation. After training the fish were pitted against each other immediately after seeing the light

Overall the winners were trained fish. A second encounter 3 days later w/no light resulted in original winners winning again.

Molecular Genetics and Endocrinology of LearningMolecular Genetics of Learning in Rats

Over the course of 40 years rats had been selectively bred for best avoidance of shock (SHA) or poorest avoidance of shock (SLA).

SLA rats have shown higher levels of anxiety and poor learningSHA rats show “fearlessness” & are better at avoidance

The rats were killed & dissected – they found:SHA rats had gene expression in Velil, SLC3al, Ptpro, & Ykt6pSLA rats had gene expression in SLC6A4/5HTT, Aldhla4, Id3a, and Cd74

SLC6A4/5HTTAssociated with serotonin – correlates w/anxiety, depression & suicidal thoughts in humans

Endocrinology of Learning in Rats

Glucocorticoids are hormones that play a role in stress responses and learningTesting was done on rats to test various hormones.

-Open “field” test

-Water maze to find submerged platform

Low anxiety rats better at spatial learning tasks & had lower levels of glucocorticoid