Why Learn? 10/11/2012. Benefit of instinct. Learning is a developmental process.

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Jeffrey Thornton
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Mechanism Development Benefit of instinct Instincts are beneficial when mistakes are not an option.

natural selection a visual cliff Example Instinctive startle response to predatory silhouette by chicks Why

Learning allows animal to modify behavior to suit the current environment.

The Problem with Instinct Instinctive behavior is inflexible. This property is sometimes exploited by enemies!

1 Learning is a developmental process. Developmental processes should also have a function and will evolve under selection. Mechanism Development Benefit of instinct Instincts are beneficial when mistakes are not an option. Example Hesitating instinctively at the edge of a cliff (ducklings, kittens, human infants) Function Evolution natural selection a visual cliff Example Instinctive startle response to predatory silhouette by chicks Why Learn? Learning is beneficial when the environment changes unpredictably. Learning allows animal to modify behavior to suit the current environment. In each example, the first mistake could be your last Learning enables environmental tracking. The Problem with Instinct Instinctive behavior is inflexible. This property is sometimes exploited by enemies! Animal mimicry involves code-breaking to varying degrees. Example. Code-breaking in colony parasites. Ants use tactile and chemical releasers to communicate with nestmates. A rove beetle parasite mimics those signals, thus breaking the code that ants use to identify nestmates. Eye mimics evoke startle response by bird predators. 1

2 Example. Code-breaking in brood parasites. Cowbirds and cuckoos lay eggs in nests of host birds. Host bird raises parasite young. male cowbird vireo feeding cowbird young Parasite species have broken the code by which young are recognized. Code involves features of egg and gaping response of baby birds. More code breaking: European Cuckoo removes host s egg. Why? Sometimes code-breaking is solved. Male wasps are fooled at first by orchids that mimic female wasps. but eventually learn to avoid those orchids! 2

Habituation waning of response to a stimulus upon repeated presentation of the stimulus Example withdrawal response of sea anemone or hydra to disturbance Habituation, a kind of non-associative

neutral stimulus is subsequently elicited Examples Pavlov s dog, honey bees, butterflies Learning has two potential costs Associative learning permits animal to predict future events saves time

3 Habituation waning of response to a stimulus upon repeated presentation of the stimulus Example withdrawal response of sea anemone or hydra to disturbance Habituation, a kind of non-associative learning, allows animal to reduce responses to meaningless stimuli UCS: red meat CS: sound of bell Associative Learning pairing of neutral stimulus with nonneutral stimulus, such that a response to neutral stimulus is subsequently elicited Examples Pavlov s dog, honey bees, butterflies Learning has two potential costs Associative learning permits animal to predict future events saves time and/or energy reduces risk of predation or parasitism Cost of being naïve Until learning occurs, behavior is a poor match to environment. E.g., the errors in trial-and-error learning Cost of becoming experienced The process of matching behavior to environment is costly. E.g., additional metabolically-expensive neural tissue Cost of being naive Even when a trait starts off as a product of learning, it does not have to remain so. Evolutionary theory, supported by computer simulations, has shown that when an environment is stable, there is a selective pressure for learned abilities to become increasingly innate. That is because if an ability is innate, it can be deployed earlier in the lifespan of the creature, and there is less of a chance that an unlucky creature will miss out on the experiences that would have been necessary to teach it. Steven Pinker (1994) The trouble with trial-and-error learning is the error. Ron Pulliam (1985) Bee trained to choose yellow over blue Proportion landings on yellow Acc d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d e m o d emodel m o Logistic d e m o y = A2 + (A1-A2)/(1 + (x/x0)^ Equation p) Reduced Chi-Sqr d e m o d e m o d e m o d e m o Visit Adj. R-Square Value Standard Error A d e m o d e m o d e m o d e m o A d e m o d e m o Acc d e m o x p d e m o EC d e m o d e m o d e m o EC d e m o Acc Logistic Fit of Sheet Arrow indicates cost of being naïve 3

Cost of becoming experienced Song learning involves specialized regions of brain.

Neural cost can vary with how much is learned West Coast marsh wrens have large song repertoires

Naïve host finding by cabbage whites cabbage white butterfly, Pieris rapae Former Papaj Lab

cues to locate host plant species on which they lay eggs.

Landings on hosts and non-hosts tallied according to color.

2 Green host Red host N = 60 females 0.5 0.4 0.3 0.2 0.

4 Cost of becoming experienced Song learning involves specialized regions of brain. Neural tissue is metabolically expensive! Learning may incur cost of additional neural tissue. Neural cost can vary with how much is learned West Coast marsh wrens have large song repertoires (100 songs); East Coast wrens have small ones (40 songs) West Coast wrens have larger song learning brain regions. Brain = 10-20% of metabolic expenditures Costs of Host Learning in Butterflies Cost of Being Naïve host finding by cabbage whites cabbage white butterfly, Pieris rapae Former Papaj Lab student, Emilie Snell-Rood Green host array Red host array Recall: Female butterflies use color cues to locate host plant species on which they lay eggs. A female placed on host and permitted to search for hosts over two days. Landings on hosts and non-hosts tallied according to color. Proportion Non-Host Landings on Green Foliage 1.0 Proportion Landings on Hosts Green host Red host N = 60 females Green host Red host N = 60 butterflies Day 1 Day Day 1 Day 2 Green bias at outset. Females in red host environment alight more on red with experience. Finding of red hosts improves more with time. Cost of being naïve thus greater on red hosts. Snell-Rood and Papaj, The American Naturalist,

Cost of Becoming Experienced neural costs in cabbage whites Innate

red host environments; Probably because green hosts are much more

mushroom bodies: brain region thought to be involved in learning in

on the cost of becoming experienced mushroom bodies Cross-section

Measure area of brain region. 2. Slice brain up. 3.

families (females within a family are full siblings).

5 Cost of Becoming Experienced neural costs in cabbage whites Innate green preference is maintained despite the cost of being naïve in red host environments; Probably because green hosts are much more common in cabbage white s range than are red hosts. mushroom bodies: brain region thought to be involved in learning in insects insect brain Whether host color learning persists, depends on the cost of becoming experienced mushroom bodies Cross-section through the brain, showing mushroom bodies 1. Dissect brains out. 4. Measure area of brain region. 2. Slice brain up. 3. Arrange slices, one brain per slide. Photo by E. Snell-Rood Photos by E. Snell-Rood Red host array Brains sampled for females from 12 families (females within a family are full siblings). Other full siblings from each family are assayed for learning ability and host finding success. mushroom bodies Genotypes that learn better emerge as adults with larger mushroom bodies, the brain region in insect involved in learning and memory in insects. = global cost, meaning cost of learning is paid whether learning takes place or not. 5

Also, mushroom body (MB) size increases more over lifetime for genotypes that are better at finding hosts Host-finding success 1 0.8 0.6 N = 6 families F = 32.

Estimates compared to those of siblings sacrificed at emergence. 0.4 0 0.001 0.002 0.

Snell-Rood, Papaj and Gronenberg, Brain, Behavior and Evolution, 2009 Operating costs found for chickadee species that store that store food TRADEOFF!

competitive ability index Do big brains in adult butterflies result in wimpy caterpillars? Hippocampus is involved in spatial memory.

6 Also, mushroom body (MB) size increases more over lifetime for genotypes that are better at finding hosts Host-finding success N = 6 families F = 32.5 P = Red host array Next, the females that learned are sacrificed, and estimates of brain size made. Estimates compared to those of siblings sacrificed at emergence Increase in relative MB volume over development = operating cost, meaning cost is paid to operate the learning/memory machinery. Snell-Rood, Papaj and Gronenberg, Brain, Behavior and Evolution, 2009 Operating costs found for chickadee species that store that store food TRADEOFF! In Drosophila strains selected for good learning ability as adults, the larvae are less competitive. competitive ability index Do big brains in adult butterflies result in wimpy caterpillars? Hippocampus is involved in spatial memory. As food is cached, hippocampus grows. Or, do adults themselves pay the cost? Adult cabbage whites pay a cost. Genotypes that learn better emerge with less well developed ovaries. Success in Finding Hosts immature ovaries mature ovaries The reproductive delay is a tradeoff associated with host-finding success, which in turn depends on effective learning. Snell-Rood, Davidowicz and Papaj, Behavioral Ecology, in press 6

7 Learning should evolve in relation to costs and benefits of learning. Does it? How might we find out? (think cuttlefish video ) If natural selection shapes learning, 1. species or populations might differ in learning, and 2. sexes might differ in learning. in ways explained by differences in ecology and life history. If natural selection shapes learning, 1. species or populations might differ in learning, and 2. sexes might differ in learning. in ways explained by differences in ecology and life history. Learning what s dangerous varies among populations in a species of stickleback. Stickleback populations vary greatly in intensity of predation. Low-predation and high-predation populations learn equally well to forage. But high-predation populations learn faster to avoid location associated with simulated predator. Differences are genetically-based. Seed-Caching in Jays Clark s nutcracker lives at treeline 100% of winter diet from caches* 33,000 seeds stored in 9,000 caches *cache = storage site Scrub jays live at lower altitudes just 60% of winter diet from caches 6,000 seeds stored in ca caches Mexican jays and pinyon jays also rely less on caching. 7

Clark s nutcracker shows superior spatial memory. Jays and Clark s nutcracker are in the Family Corvidae, along with crows and ravens. All considered to be smart.

Retention interval (sec) Retention interval (sec) Spatial task location of circle Nonspatial task color of circle Corvus moneduloides TED video by Joshua Klein YouTube

Why a requirement for such intelligence in such a place? Nobody knows. If natural selection shapes learning, 1. species or populations might differ in learning, and 2.

8 Clark s nutcracker shows superior spatial memory. Jays and Clark s nutcracker are in the Family Corvidae, along with crows and ravens. All considered to be smart. But none more so than the New Caledonian crow. Retention interval (sec) Retention interval (sec) Spatial task location of circle Nonspatial task color of circle Corvus moneduloides TED video by Joshua Klein YouTube videos by Russell Gray New Caledonian crows are found on the island of New Caledonia off the coast of Australia. Why a requirement for such intelligence in such a place? Nobody knows. If natural selection shapes learning, 1. species or populations might differ in learning, and 2. sexes might differ in learning. If natural selection shapes learning, 1. species or populations might differ in learning, and 2. sexes might differ in learning. in ways explained by differences in ecology and life history. in ways explained by differences in ecology and life history. 8

Spatial Memory Differences in Voles Male meadow voles have a larger hippocampus, consistent with their better spatial memory.

Meyers Meadow vole males are polygynous (= mate with multiple females) Males thus have large home ranges Pine vole males are monogamous (= mate with a single female) Hippocampal Vol.

9 Spatial Memory Differences in Voles Male meadow voles have a larger hippocampus, consistent with their better spatial memory. Home range size (m 2 ) males 600 females Meadow Pine Spatial Ability Rank Meadow Pine Both species and gender affect spatial ability. Rel. Hippocampal Size Meadow Pine males females Mating system drives differences in learning Tables are turned in cowbirds! P. Meyers Meadow vole males are polygynous (= mate with multiple females) Males thus have large home ranges Pine vole males are monogamous (= mate with a single female) Hippocampal Vol. (mm 3 ) Cowbird Red-Winged Blackbird males females Grackle Female cowbirds have larger hippocampi than males. WHY? Among jay species or gender, vole gender and stickleback populations, learning differs according to differences in the benefit of learning. But differences in costs could also affect patterns in learning. Understudied! Do different forms of learning have different costs? Can animals select form of learning that is of more benefit? e.g., personal learning versus social learning 9

Fig. 5.1 1950 s Koshima Islet Japan A Japanese macaque named Imo Other macaques copied sweet potato washing.

Later wheat washing Social Learning Observational Learning kind of learning in which animal learns behavior

animal learns something related to a behavior while observing another animal engage in that behavior

1992 Study Demonstrator octopus rewarded with fish for attacking red ball and with shock for attacking

10 Fig s Koshima Islet Japan A Japanese macaque named Imo Other macaques copied sweet potato washing. Soon many macaques washed sweet potatoes before eating. Later wheat washing Social Learning Observational Learning kind of learning in which animal learns behavior faster or exclusively in the company of other individuals involves model (or demonstrators) and observer(s) animal learns something related to a behavior while observing another animal engage in that behavior Involves demonstrators and observers Observational Learning in Octopus? 1992 Study Demonstrator octopus rewarded with fish for attacking red ball and with shock for attacking white ball. Observational Learning in Octopus cont d Next, observers watched demonstrators attack red ball (with neither observer or demonstrator being rewarded with fish). Hmm Demonstrator Observer 10

Observational Learning in Octopus cont d What happens when you put a red and white ball into the tank of an observer? Observer The observer attacked the red ball!

This question requires us to understand the ecology of a species. What are costs and benefits of social learning? Tool use involves observational learning Example.

11 Observational Learning in Octopus cont d What happens when you put a red and white ball into the tank of an observer? Observer The observer attacked the red ball! Learning was faster than for demonstrator! BUT First evidence of observational learning in an invertebrate If octopi aren t social, when are they watching each other? This question requires us to understand the ecology of a species. What are costs and benefits of social learning? Tool use involves observational learning Example. Chimpanzees fish for termites Why not just use trial-and-error learning? Tradeoff with Social Learning Benefit: Watching takes less energy than inventing the technique Benefit: And inventions are a rare thing Cost: But watching and remembering may require well-developed cognitive abilities. When to Copy 1. When observation of conspecifics is easy. 2. When asocial sampling is especially difficult or costly. 11

Who to Copy Show guppies (Poecilia reticulata) Use both personal and social information to learn location of feeders Rely more

Individuals you spend time with 2. Individuals with more experience (= older) 3.

Behavioral Ecology 2004 Apparently social learning and individual learning differ in costs and benefits.

12 Who to Copy Show guppies (Poecilia reticulata) Use both personal and social information to learn location of feeders Rely more on social information when gathering personal information is made riskier (= loss of contact with shoal) 1. Individuals you spend time with 2. Individuals with more experience (= older) 3. Individuals you can trust (= parents, other relatives) 4. Individuals who are successful Kendal et al. Behavioral Ecology 2004 Apparently social learning and individual learning differ in costs and benefits. Evening bats (Nycticeius humeralis) Raise young in communal nurseries Unsuccessful foragers follow successful ones to food sites Following results in better success in prey capture What about learning versus not learning (= instinct)? 12

We know that humans can learn

We know that humans can learn Learning in Animals Which animals are able to learn? (Hint: all animals have nervous systems) Reasonable guess: All animals can learn!! (Def.) Learning is a relatively long-lasting