Transcript Chap3aAlt
PSY 402 Theories of Learning Chapter 3 – Nuts and Bolts of Conditioning (Mechanisms of Classical Conditioning) Classical vs. Instrumental The modern view is that these two types of learning involve similar learning processes, but differ in the following ways. 1. 2. In Classical conditioning, two stimuli are associated with each other but in Instrumental conditioning, a stimulus and a response are associated. In Classical conditioning, the response is a reflex or involuntary action but in Instrumental conditioning, the response is a voluntary, freely emitted behavior. Pavlov’s Conditioned Reflex Conditioning -- a stimulus that initially produces no response can acquire the ability to produce one. Learning occurs through pairing in time and place of one stimulus with another stimulus that produces an involuntary response. Terminology of Conditioning Unconditioned stimulus (US or UCS) Elicits a reflexive response without learning. Unconditioned response (UR or UCR) The response that occurs with a US, typically a reflex, emotion or drug state Involuntary and automatic. More Terminology Neutral stimulus Conditioned stimulus (CS) A stimulus not capable of producing an unconditioned response (before learning). A previously neutral stimulus that has acquired the ability to evoke a response. Conditioned response (CR) The learned response, often similar to the UCR, an involuntary reflex, emotion or drug state. Prior to conditioning Neutral stimulus (tone) (Orientation to sound but no response) UCS (food powder in mouth) UCR (salivation) During Conditioning Neutral stimulus CS (tone) + UCS (food powder) CR (salivation) After conditioning CS (tone) CR (salivation) Conditioning Processes Stimulus generalization – stimuli like the CS become able to evoke the conditioned response. Extinction – if the UCS and CS are not paired, the CS loses its ability to produce a conditioned response. Spontaneous recovery – an extinguished CS briefly returns but quickly goes away again. What is Learned? Pavlov believed the association was between the two stimuli (tone and meat powder), not between the tone and salivation. Either is possible Stimulus substitution Conditioning Situations Sign-tracking (autoshaping) – animals must recognize signs of food (UCS) and respond (UCR). Pigeons pecking at key. UCR, not an operant response, because behavior is specific to the stimulus. Eyeblink conditioning UCR is rapid, CR is slow. Many trials are needed (100 pairings) Conditioned Emotional Responses Fear is an anticipatory pain response based on past experience. Fear is conditioned (becomes a CR) whenever a CS is associated with an aversive (painful or undesirable) event. Fear motivates two responses: Escape (when pain is present) Avoidance (when pain is imminent) Fear conditioning Avoidance is not a good measure of fear. Suppression of an operant behavior occurs with a feared stimulus. First – an operant behavior is learned. Second – a CS is paired with an aversive UCS. Third – the CS is presented in the operant chamber and the effect on operant responding is measured. Suppression Ratio During CS Suppression Ratio = During CS + Without CS The amount of time during and without the CS is equal. The more fear, the lower the suppression ratio. Ratios typically fall between 0 and .5 This will be on the midterm Flavor Aversion Learning Garcia – rats will not drink water with saccharin if they get ill after drinking. Significant avoidance occurs after just one trial. Human food aversions are related to illness (89%). Even if illness occurs hours later it is linked to the previous meal. Not cognitive – you can know the food is not to blame and still feel an aversion to it. 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. Factors Affecting Conditioning Timing – how closely in time are the CS and UCS, and which occurs first. Novelty of the CS and UCS. Intensity (strength) of the CS and UCS. Consistency of the pairing between the CS and UCS. If one or the other appears alone then conditioning is weakened. Stimulus Presentation Paradigms Delayed conditioning – the CS onset precedes the UCS onset. Trace conditioning – the CS starts and ends before the UCS onset. Simultaneous conditioning – the CS and UCS occur together. Backward conditioning – the UCS starts and ends before the CS onset. These paradigms will be on the midterm Massed vs Spaced Trials Better learning occurs when trials are spaced out over time (spaced), rather than bunched together (massed). Memory consolidation or rehearsal may be needed between trials. The ratio between the exposure to the CS and the time in-between is the important factor. If both are the same duration, learning is weaker. Importance of Novelty Preexposure to the CS (before it is paired with the UCS) reduces learning. The same thing happens with preexposure to the US (before it is paired with the CS). Called latent inhibition because it inhibits learning of the CS-UCS association. Called the US preexposure effect Other, more novel stimuli are more likely to become associated with the UCS. Stimulus Intensity (Strength) The stronger the US (UCS), the faster the learning and the stronger the association. The stronger the CS, the better the learning. Salience – how attention-getting the stimulus is in relation to other stimuli in the environment. The most salient CS becomes associated with the UCS. An overpowering CS may elicit a response of its own, preventing learning. Pseudo-conditioning Responses to the CS may occur due to the strength of the UCS, not learning. Once air has been puffed at the eye, blinking may occur in response to any stimulus that comes next, without any learning. Sensitization resulting from an intense UCS may cause the response to a CS to be increased, even when there is not greater learning. A control group lets you tell the difference.