07_learning '09

07_learning '09 - 9/14/2009 1 Mechanism Learning is a...

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Unformatted text preview: 9/14/2009 1 Mechanism Learning is a developmental process. Learning is a developmental process. It should also have a function. It should also have a function. Development Function Evolution natural selection What What are the are the relative costs relative costs and benefits of and benefits of learning and learning and instinct? instinct? Benefit of instinct Benefit of instinct Instincts are beneficial when mistakes are not an option. Example Hesitating instinctively at the edge of a cliff Hesitating instinctively at the edge of a cliff (ducklings, kittens, human infants) a visual cliff a visual cliff Example Instinctive startle response to predatory silhouette by chicks In each example, the first mistake could be your last Cost of instinct Cost of instinct Instinctive behavior is inflexible . This property is sometimes exploited by enemies! 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. Example . Code-breaking in brood parasites . Cowbirds and cuckoos lay eggs in nests of host birds. Host bird raises parasite young. male cowbird male cowbird P i t i h b k vireo feeding cowbird vireo feeding cowbird young young Parasite species have broken the code by which young are recognized. Code involves features of egg and gaping response of baby birds. 9/14/2009 2 Animal mimicry involves code Animal mimicry involves code-breaking to breaking to varying degrees. varying degrees. Eye mimics evoke startle response by bird predators. Sometimes code-breaking is solved. Male wasps are fooled at first by orchids that mimic female wasps. but eventually learn to avoid those orchids! Benefit of learning Benefit of learning Learning is beneficial when the environment changes unpredictably . Learning allows animal to modify behavior to suit the current environment. Learning enables environmental tracking . Habituation Habituation waning of response to a stimulus upon repeated presentation of the stimulus Example withdrawal response of sea anemone or hydra to disturbance Habituation allows animal to reduce responses to meaningless stimuli Associative Learning Associative Learning UCS: red meat CS: sound of bell pairing of neutral stimulus with nonneutral stimulus such that response to neutral stimulus is subsequently elicited Examples Pavlovs dog, honey bees, butterflies Associative learning permits animal to predict future events saves time and/or energy reduces risk of predation or parasitism 9/14/2009 3 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 Cost of Cost of being naive...
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07_learning '09 - 9/14/2009 1 Mechanism Learning is a...

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