Transcript LTJan10
Prior to conditioning Neutral stimulus (tone) (Orientation to sound but no response) UCS (food powder in mouth) UCR (salivation) Conditioning Neutral stimulus CS (tone) + UCS (food powder) CR (salivation) After conditioning CS (tone) CR (salivation) Watson & Raynor Human fears can be acquired through Pavlovian conditioning. Rat paired with loud noise Stimulus generalized to other white objects (white rabbit, white fur coat) Mary Cover Jones developed a technique for eliminating conditioned fears. Acquisition of fear-inhibiting response Modification of Instinctive Behavior Chapter 2 Instinctive Systems Lorenz & Tinbergen – evolution occurs when a species incorporates environmental knowledge into its genetic structure. Greylag goose and egg-rolling. Learning can sometimes modify instinctive behavior – even though the fixed action patterns are innate. Energy Model Action-specific energy builds up but is blocked (inhibited). The energy motivates appetitive (approach) behavior. Presence of a sign stimulus releases the energy by stimulating an innate releasing mechanism. The behavior occurs as a fixed action pattern (or chain of actions). Releasing Signs Releasing signs can be complex: Grayling butterfly signs include darkness of female, distance from male, and pattern of movement. Intensity of the sign influences the behavior but so does the amount of accumulated energy (time since the last response). Hierarchical System Specific behaviors are controlled by a central instinctive system. Energy can accumulate at each level in the system. Hormones generate energy. Release of energy at higher levels flows to lower levels. The sign stimulus determines which behavior will occur. Conflicting Motives If two incompatible signs appear at the same time, energy flows to a third instinct system. This third behavior is called displacement. Conditioning Affects Behavior Conditioning experiences can change sensitivity to releasing signs. Only the consummatory response at the end of a chain cannot be changed. Conditioning fine tunes the response to the environment and enhances survival. Criticisms of the Energy Model Best viewed as a metaphor. The brain does not literally accumulate energy in any centers and nothing flows. Willows & Hoyle – alternating contractions in sea slug allow it to escape from a starfish. Brain areas producing this response do not correspond to energy model. Acquired Changes in Response Habituation – response to a repeated stimulus decreases with experience. Sensitization – response to a repeated stimulus increases with experience. Examples: Ingestional neophobia, fear of new food Startle response Experimental Evidence Rats drink little saccharin water at first but increase over time. Loud tones (110 db) produce different responses depending on the background noise (60 vs 80 db). Habituation occurred at 60 db Sensitization occurred at 80 db A loud background is arousing, leading to greater reactivity, not less. Conditions Producing Change More intense (stronger) stimuli produce stronger sensitization, less likely to produce habituation. Greater sensitization and habituation occur when the stimulus is repeated frequently. Changes in the stimulus prevent habituation. Turkeys respond to shape changes. Conditions (Cont.) Sensitization can occur to many kinds of stimuli but habituation occurs only with innate responses. Habituation and sensitization are transient (go away after seconds or minutes between stimuli). Except long-term habituation. Dishabituation – response returns when a sensitizing stimulus occurs. Opponent-Process Theory An explanation for addictions. All experiences produce an affective reaction (pleasant or unpleasant) – A state. This reaction gives rise to its opposite – B state. B state is less intense and lasts longer. Over time, the A state diminishes and the B state increases. The Addiction Process Tolerance – diminished A state. Withdrawal – increased B state. Addictive behavior is a coping response to the change in B state. People try to enhance A state to offset the unpleasantness of the B state. Without withdrawal symptoms there is no addictive behavior. Time prevents B state strengthening. What Sustains Addiction? The B state is a non-specific aversive feeling. Anything similarly aversive will motivate the addictive behavior, even if it has no relation to the substance. Daily life stress produces a B state that results in behavior to create an A state. Parachute jumpers – create a B state in order to feel the A state.