Transcript PSY 402
PSY 402 Theories of Learning Chapter 2 – Learning and Adaptation Learning Enables Adaptation The ability to adapt to one’s environment with experience enhances survival. Those organisms able to adapt were more likely to survive and thus were selected by natural selection. Example of survival value of a behavior: Black-headed gulls and eggshells Kittiwakes who nest on cliffs don’t remove shells 2.1 Eggshell removal in herring gulls Fixed Action Patterns Fixed behavior sequences that are released by an environment signal. Triggered by a releaser, also called a sign stimulus Not learned – built in to the genes, innate Stereotyped – occur the same way each time and in each person or organism Eibl-Eibesfeldt considered smiling & eyebrow flashing to be a human fixed action pattern. 2.2 The eyebrow flash in Bali and Papua New Guinea Modification of Innate Behaviors Even behaviors that are innate can be modified through conditioning. Gull chicks get better at pecking at their parents’ beaks to get food – more accurate. Conditioning experiences can change sensitivity to releasing signs. Conditioning fine tunes the response to the environment and enhances survival. Acquired Changes in Response Habituation – response to a repeated stimulus decreases with non-threat experience. Sensitization – response to a variety of stimuli increases with a single threat experience. Examples: Ingestional neophobia, fear of new food Rats orient less toward light, startle decreases Chicks are less frightened by shadows flying overhead with repeated exposure. 2.3 Habituation occurs when exposure to a stimulus elicits a response (Part 1) 2.3 Habituation occurs when exposure to a stimulus elicits a response (Part 2) 2.3 Habituation occurs when exposure to a stimulus elicits a response (Part 3) Instrumental Adaptation Instrumental learning (S-R) occurs when a voluntary behavior (R) becomes associated with a stimulus (S) because of its effect. Consequences can be either rewards or punishments. Rewards and punishments are defined by their effect on behavior. A reward increases behavior A punishment decreases behavior. 2.4 The Law of Effect Reinforcement Reinforcement occurs when the association between a stimulus and a response to it is strengthened. Positive reinforcement occurs when a behavior is rewarded. Negative reinforcement occurs when a behavior results in avoidance or escape from a bad consequence. Shaping How can a behavior be reinforced if it never occurs naturally (or accidentally)? Shaping is a process where a complex or unnatural behavior is learned as a series of steps that are successively rewarded. By rewarding successive approximations to the desired behavior, eventually the target behavior is learned. 2.5 Shaping introduces new behaviors Classical Conditioning Adaptation Organisms learn to recognize and respond selectively to the signals that are important in their environment. Cues associated with food evoke digestion: salivation, gastric juices, insulin secretion. Taste aversion learning – illness makes us avoid foods that were eaten just prior to feeling sick. Food preferences are associated with nutrients. Examples of Conditioning Popcorn at the movies. Fear of flying -- stronger with more turbulence (a stronger UCS). An antelope shying away from low tree branches. Nausea at the smell of alcohol after a hangover. Territoriality Environmental cues can become associated with sexual rival males in gourami fish. Pairing the light with the rival signaled the other fish to prepare so it was able to be more aggressive. Presenting the light without pairing it with the rival had no effect. Courtship behavior can also be conditioned, leading to more successful nestbuilding, etc. Fear Conditioning Freezing is a universal response to threat. Animals that freeze are less likely to be attacked. Fear is an anticipatory pain response. It occurs in response to stimuli that have been aversive in the past and motivates escape or avoidance behaviors. Fear also releases endorphins in rats who are confronted by the smell or sight of a cat. Conditioning and Addictions Drugs can be associated with environmental cues present when the drugs are taken. Instead of the drug response being conditioned, an opposite adaptive response is conditioned that lessens the drug’s effect. This is called drug tolerance. Taking a drug under novel circumstances can produce a drug overdose because the compensatory effect is not present (no cues). 2.9 The development of drug tolerance Sign Tracking (Auto-Shaping) Sign tracking occurs when a stimulus (cue) in the environment is associated with reward or punishment. The sign stimulus motivates approach or avoidance behavior because of what it signals. Negative sign tracking occurs when a sign motivates withdrawal instead of approach. Some signs signal safety because they mean a bad thing is less likely to occur. 2.11 Sign tracking in Pavlovian learning Extinction Associations are learned when they enhance survival, but conditioning decreases when the expected consequence no longer occurs. Extinction occurs with both instrumental and classical conditioning. Spontaneous recovery occurs after extinction has been learned, but a break in exposure to the stimulus occurs. After spontaneous recovery, extinction returns. 2.12 Extinction occurs in instrumental conditioning (Part 1) 2.12 Extinction occurs in classical conditioning (Part 2) Timing of Stimuli The strength of both instrumental and classical conditioning depends on the timing of events. Reward or punishment must immediately follow the emitted response in order to strongly affect behavior. Two stimuli must occur close together in time in order for them to be associated with each other. 2.13 Reward and Punishment (Part 1) 2.13 Reward and Punishment (Part 2) 2.14 Classical conditioning is better when the interval between S and S* is minimal (Part 1) 2.14 Classical conditioning is better when the interval between S and S* is minimal (Part 2) 2.14 Classical conditioning is better when the interval between S and S* is minimal (Part 3) Size of the Stimuli The strength of both instrumental and classical conditioning also depends on the size of the stimuli. Larger rewards produce a stronger response than smaller ones. More intense stimuli are better signals and evoke greater conditioned responses. More fear, more saliva. 2.15 Bigger S*s cause better response learning (Part 1) 2.15 Bigger S*s cause better response learning (Part 2) 2.16 Bigger S*s cause better stimulus learning, too (Part 1) 2.16 Bigger S*s cause better stimulus learning, too (Part 2) Preparedness Affects Learning Both instrumental and classical conditioning are affected by preparedness (the innate nature of the organism). Flavor aversion learning is easier with taste cues than with visual cues, but not shock. Rooting behaviors interfere with learning for pigs trained to put a wooden coin in a “bank”. Some hamster behaviors are easier to learn. 2.17 Preparedness in classical conditioning 2.18 Preparedness in instrumental conditioning Humans Show Preparedness Humans show preparedness too, appropriate to our species. Nausea can be associated with tequila but not with friends or a shot glass. Snake and spider phobias may be especially prevalent due to preparedness. People associate shock with spiders or snakes more readily than with flowers or mushrooms.