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Learning Part I Learning Classical Conditioning

Study of learning Learning: process by which long-lasting changes occur in knowledge/behavior as a result of experience Has to be long-lasting: needs to reach a relatively permanent state. fatigue would be excluded. Has to be due to experience and not some physical change (hormones, injury, aging, etc)/

Two approaches to study learning Behaviorism (early 20th century) studied simple learning mechanisms introduction of stimulus-response theories focus on animal studies Cognitivism (1950s-present) introduction of complex mental processes (“inside the mind”) focus on human learning Behaviorists believed that animal learning allows researchers to study learning in a purer form, uncontaminated by culture and language Animal experiments were also subject to fewer ethical constraints Sea slugs have been used and are still used

Nonassociative forms of Learning Habituation: An organism’s response to a stimulus will decline following repeated presentations of a stimulus. Dishabituation Presentation of a novel stimulus leads to an increase in responsiveness Habituation, a decreased tendency to respond to stimuli that have become familiar, is perhaps the simplest form of learning, and it occurs at virtually all levels of the animal kingdom. It serves an important adaptive function by limiting the range of stimuli that provoke escape reactions from an organism. One is better able to focus on what is new if there is a way to ignore that which has already become familiar. Just as important for survival is dishabituation, an increase in responsiveness caused by the presentation of something novel. In addition to being an interesting form of learning, habituation has proved to be very useful as a means for studying the perceptual abilities of young infants. Habituation has both benefits and costs. Thanks to habituation, the bison of Wyoming’s Yellowstone Park have grown accustomed to the automobile traffic. This is helpful for the bison—but it may be less helpful for the traffic. Similarly, many city residents have become habituated to the sight of homeless people on the street—a sad fact that may undermine people’s motivation to help them.

Using habituation to study infant cognition 2-month old infant 4-month old infant Looking time Looking time No habituation habituation dishabituation Repeated observations of Object 1 Present Object 2 Repeated observations of Object 1 Present Object 2 With these techniques, it has been found that babies can discriminate between faces and voices. Within nine months, can tell difference between happy and sad faces. They know biological motion.

Video: habituation (40 secs) (for original video, see: http://www.youtube.com/watch?v=UiB2ZX1phmc&feature=related)

Classical Conditioning In classical conditioning, animals learn about the association between one stimulus and another. In classical conditioning is a type of learning, a neutral stimulus gets associated with a unconditioned stimulus and it gets to trigger a response (the unconditoned response). Examples of classic conditioning: Pavlov dogs / Little Albert / Being Disciplined (spanked). reflexive learning Pavlov was a physician that studied digestion. In contrast to habituation, in which the organism only learns to recognize an event as familiar, other forms of learning require the animal to form an association. Pavlov was one of the first to study such associations experimentally. His studies introduced the four major components of the classical conditioning procedure: the unconditioned stimulus (US), the unconditioned response (UR), the conditioned stimulus (CS), and the conditioned response (CR). The US elicits the UR automatically and without prior learning (e.g., food powder automatically elicits salivation). The CS initially elicits no response, but after repeating pairings of the CS and the US, the CS comes to elicit the CR. Classical conditioning has been demonstrated in a remarkable range of species (from cockroaches to octopi) and circumstances. An example in humans is the emotional experience triggered by certain smells or a familiar song. One of Pavlov’s dogs Ivan Pavlov 1849-1936 Nobel Laureate

Video (~3 min.) Tube collected saliva Presented meat powder and then measured the response in term of salivation Dog started to salivate not only in response to the meat powder but to other “neutral” stimuli. Such as guy bringing in food. Footsteps of the guy bringing in food.

Acquisition of a conditioned response Salivation is a physiological reflex to food. Unconditioned response A tone is presented at the same time as the food. An association between the tone and food is established. In contrast to habituation, in which the organism only learns to recognize an event as familiar, other forms of learning require the animal to form an association. Pavlov was one of the first to study such associations experimentally. His studies introduced the four major components of the classical conditioning procedure: the unconditioned stimulus (US), the unconditioned response (UR), the conditioned stimulus (CS), and the conditioned response (CR). The US elicits the UR automatically and without prior learning (e.g., food powder automatically elicits salivation). The CS initially elicits no response, but after repeating pairings of the CS and the US, the CS comes to elicit the CR. Classical conditioning has been demonstrated in a remarkable range of species (from cockroaches to octopi) and circumstances. An example in humans is the emotional experience triggered by certain smells or a familiar song. After training, the tone presented alone will elicit salivation. The UR and CR are similar, but not necessarily identical.

Acquisition and extinction of a conditioned response 7.8 Extinction of a classically conditioned response The figure shows the decrease in the amount of saliva secreted (the CR) with increasing number of extinction trials—that is, trials on which the CS is presented without the US. However, if the animal then spends a short amount of time away from the conditioning apparatus, the CR will reappear the next time the animal encounters the CS—a pattern known as spontaneous recovery. A conditioned response is not permanent. If the tone is repeatedly presented without food, the salivation response will gradually decay. These findings show that there are general laws of learning. Exposure therapy can seemingly extinguish a conditioned fear response but spontaneous recovery can occur. Therapy needs to generalize stimuli, context, environment. Important Question At some point, even spontaneous recovery will be completely extinguished. Has the association been erased? No. If the dog is reconditioned following complete extinction, fewer pairings of food (US) and tone (CS) will be required to reestablish the salivation response to tone alone.

Examples of US-UR pairings Stimulus (US) / Response (UR): Food / Salivation Electric shock / Pain reaction Food / Nausea Puff of air / Eye blink In classical conditioning, a response is elicited. In operant conditioning, a response “operates on the environment” Insulin injection / Lower blood sugar level

Video: conditioned eyeblink response (~2 min.) cerebellum is involved in the neuronal circuit Original video: http://www.youtube.com/watch?v=Xg3WuvCrIZg

Major Phenomena of Classical Conditioning Second-order conditioning Generalization Discrimination Temporal ordering Contingency Blocking

Second-order conditioning (1) US (food) paired with CS1 (metronome) (2) CS2 (light) is followed by CS1 (metronome) followed by no food (3) CS2 (light) alone elicits CR (salivation), although at a reduced level Learning is based on establishing associations Complex behaviors are assembled from simple ones

Generalization Training Pair a 1200 Hz tone with the US Testing Generalization Gradient Training Pair a 1200 Hz tone with the US Testing Measure the CR when tones with different frequencies are presented If an animal is presented with a stimulus that is sufficiently similar to the CS, there will be stimulus generalization: the animal will tend to make a CR to this new stimulus. The more the new stimulus differs from the original CS, the weaker the generalized CR will be. Generalization gradient of a classically conditioned response This figure shows the generalization of a conditioned blinking response in rabbits. The CS during the initial conditioning was a tone of 1,200 hertz, and the US was electric shock. After the conditioned response to the original CS was well established, generalization was measured by presenting various test stimuli and noting the percentage of trials in which the animals produced the CR. Food aversion and generalization gradient – what places/foods will you avoid after a stomach flu?

Temporal Ordering Green – CS Red - US What is the underlying cause of the association between the US and CS? Pavlov thought that temporal contiguity is the primary causal factor underlying the association. Although temporal contiguity is an important factor, it is not the primary cause. 7.10 The CS-US interval in classical conditioning The figure shows the results of a study of the effectiveness of various CS-US intervals in humans. The CR was a finger withdrawal response, the CS a tone, and the US an electric shock. The time between CS and US is plotted on the horizontal axis; negative values indicate that the CS arrived after the US. The vertical axis indicates the strength of conditioning.

Contigency The primary causal factor for establishing an association between the US and CS is contingency The CS should be informative about the arrival of the US

Contingency: an example US no US CS 40% 60% no CS 40% 60% Lack of Contingency: The CS is not informative and no conditioning occurs US no US CS 40% 60% no CS 20% 80% Shows that the CS should be informative In both cases, US follows CS in 40% of cases Positive Contingency: the US is more likely when the CS occurs and less likely when the CS does not occur. Conditioning occurs.

CS should provide new information about US: the blocking effect BLOCKING: Training Phase 1 Training Phase 2 Test Phase Pair CS1 with US Pair CS1 and CS2 with US Test CS2 alone (establish association) tone with shock tone and light with shock test light alone; no response (CR) There is no new or independent information provided by CS2. No conditioning occurs to CS2 .because it provides no new information about the arrival of the US.

What is the conditioned response (CR)? The CR may a version of the UR e.g. salivating to food might be the same as salivating to a bell The CR may also be quite different from the UR it might be a preparatory response to the US organism might prepare a response that is adaptive for the US

Compensatory conditioning Sometimes the preparation takes the form of a compensatory response Examples: drug addiction and drug tolerance The “pre-game jitters” often experienced by athletes may result from increased blood sugar levels, a conditioned response to the anticipation of intense physical activity. It is important to note that in conditioning, the CR is often similar but not identical to the UR. In the case of fear conditioning, for example, the CR is fearful anticipation rather than the UR to the unconditioned aversive stimulus. The CR is more likely to be a useful form of preparation for the arrival of the US. In some cases, such as certain drug reactions, this preparation is the very opposite of the UR and may represent a tendency to compensate for the effects of an anticipated UR, to help the system maintain homeostasis. This process is evident in how the body prepares for the effects of drugs, including insulin, caffeine, and morphine, and explains why people experience drug tolerance and cravings

Video: Little Albert (~3 min.) Conditioned Emotional Responses “little Albert’s” fear of rabbits fear of dentists ● treatment of phobias fear of snakes fear of heights ● marketing products are often paired with an attractive model John B. Watson 1878-1958 http://www.youtube.com/watch?v=0FKZAYt77ZM