What makes effective Conditioned and Unconditioned Stimuli? Classical conditioning procedures do not always result in learning Just pairing two stimuli together does not necessarily result in information being stored in the brain, depends on: – timing of stimuli – characteristics of the CS – characteristics of the US

Initial responses to the stimuli CS – does not elicit the CR initially (usually biologically weak) US – elicits the target response without any special training (usually biologically strong) Identification of CS and US can be relative – A particular event may serve as a CS relative to one stimulus and serve as a US relative to another stimulus – Sucrose food pellets – a tasty treat that rats like Sucrose food pellets can serve as the CS in a taste-aversion experiment where illness is the US The same sucrose food pellets could serve as the US in sign tracking – light ---> Saccharin pairings in a sign tracking procedure (in this case sweet taste is a proxy for food) – The animal would approach the light – Food is a special case because it has sensory cues, visual, odor, taste as well as biological consequences, nutrition, toxins and so on – Some stimuli are biologically weak Quiet sounds, dim light, constant touch

The Novelty of Conditioned and Unconditioned Stimuli The behavioral impact of a stimulus depends on its novelty Familiar stimuli do not elicit as vigorous a response as do novel stimuli (i.e., Habituation) Stimulus novelty is also important for classical conditioning If the CS and/or the US are familiar, conditioning proceeds more slowly than if they were novel (note: can still get conditioning) Testing the role of stimulus novelty involves 2 phases: – (1) preexposure of the stimulus only – (2) conditioning of CS – US

CS-Preexposure effect or Latent Inhibition Phase 1: Preexposure - Subjects are given repeated presentations of the CS alone – is similar to habituation because the repeated preexposure to the CS limits the processing of, or attention to the stimulus – is due to a stimulus-specific decline of attention – more processing of new inputs and less processing of older unimportant ones – helps preserve limited attentional resources Phase 2: Conditioning - Subjects are given pairings of the CS with the US – Preexposore of the CS retards learning Recent models of latent inhibition are based on retrieval competition concepts

Evidence That latent inhibition Is Modulated by Attentional Processes modulation of latent inhibition by attentional processes that are governed by attentional variables latent inhibition is reduced by manipulations that maintain or restore attention – a second, neutral, stimulus is paired with the target stimulus on each of its preexposure presentations (masking task) – salience of the stimulus CS-preexposure effect or Latent Inhibition

produce behavioral effects that are purportedly related to schizophrenia. behavioral tests have been latent inhibition, prepulse inhibition of the acoustic startle response, or social interaction latent inhibition measures for Schizophrenia based on the assumption that latent inhibition effects in animals and humans are governed by the same attentional processes selective attention disorder, as represented by high distractibility, is central to schizophrenia nonmedicated acute schizophrenia patients show reduced latent inhibition compared to normal subjects latent inhibition can be demonstrated with reaction time (RT) to a target stimulus (the US) which is predicted by a cue (the CS). healthy subjects show latent inhibition during the early stages of the formation of the cue–target associations and that latent inhibition would be attenuated with further cue–target pairings, chronic schizophrenia less have latent inhibition initially but have perseveration of latent inhibition Latent Inhibition Models of Schizophrenia

Nature of Attentional Dysfunction in Schizophrenia the amount of attention allocated to a stimulus is equivalent to the amount or depth of processing normal latent inhibition depends on a shift in processing mode from controlled to automatic The disrupted latent inhibition in schizophrenia patients is due to a failure to shift from controlled to automatic processing Latent Inhibition Models of Schizophrenia

US-preexposure effect Experiments on the importance of US novelty are designed in a similar way to CS novelty Phase 1: Preexposure - Subjects are given repeated presentations of the US alone Phase 2: Conditioning - Subjects are given pairings of the CS with the US The initial preexposure to the US usually retards subsequent Conditioning This may be due to conditioning of background cues during the preexposure phase Pre-exposure effects have two explanations – Associative Interference - stimuli are less able to form associations – Memory Interference - memory of preexposure interferes with memory of conditioning

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

CS and US Intensity and Salience Stimulus salience – refers to the significance or noticeability of the stimulus – Within limits Learning occurs more rapidly with more salient, or more noticeable stimuli – Intensity increases salience due to greater noticeability – Stimuli relevant to the biological needs of the animal (i.e., can increase the salience of a salt taste by depriving the animal of salt) CS Salience – A more intense CS also results in better conditioning This makes sense from an ecological point of view a more intense CS will be more salient than the background and will command more attention With CTA, a stronger concentration of flavor results in bigger taste aversions – using a CS similar to stimuli animals might encounter in the natural environment such as realistic quail models, see figure 4.2

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

CS-US Relevance, or Belongingness Rate of Classical Conditioning is also affected by the extent to which the CS is relevant to or belongs with the US – Some CS-US combinations are better than others i.e. – Genetic predisposition for selective associations between certain combinations of CSs and USs – The importance of stimulus relevance was demonstrated in an experiment by Garcia & Koelling (1966) see figure 4.3 and figure 4.4 They compared learning about peripheral pain (footshock) and learning about nausea type of illness In nature, rats are likely to get sick after eating poisonous food, but experience peripheral pain after an encounter with a predator Rats that got poisoned decreased saccharin consumption Rats that got shocked decreased consumption of the ‘bright and noisy’ water This experiment suggests that tastes are more readily associated with sickness than with shock (peripheral pain) and that audiovisual cues (LN) are more readily associated with pain/shock than with sickness We see evidence of this selectivity of association in other species – For example, certain birds locate food by its visual characteristics, rather than by its taste, rats find food mostly by odor, foxes use auditory information

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Learning without an Unconditioned Stimulus In the early research on classical conditioning the US - UR relationship was seen as essential for learning Some sort of physiological reflex or response system that could be conditioned with a sensory cue the CS This is OK for many basic examples such as salivary reflex, eyeblink or even nausea from eating bad food However there are applied situations that are more complex then this where identifying a US - UR relationship may not be possible Cues in the environment, such as sounds, odors or visual stimuli can be associated with each other. Wolves may detect an odor, hear a sound and see some movement while searching for food before actually getting contact with the food.

Higher-order Conditioning Historical background – CSs often elicit fewer and weaker responses than the US – Pavlov considered the difference in “biological strength” between CSs and USs to be necessary for their effectiveness as CSs and USs – Initially, the CS is weaker than the US – But after conditioning, the CS is strong and elicits a vigorous response – Could the strong CS now serve as a US? Procedure : See figure 4.5 – A stimulus (CS) that has become strongly conditioned may serve as a US – CS1(tone) - US(food); CS1(tone) -> CR (first-order) – CS2(light) - CS1(tone); CS2(light) -> CR (second-order) – CS3(buzzer) - CS2(light); CS3(buzzer) -> CR (third-order) Examples – Money is a powerful CS for humans although money is not always closely paired with a US buy some food and then eat the food later – Crowds can be a powerful fear stimulus (CS) for some people without ever being paired with an aversive US.

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.

Sensory Preconditioning Both stimuli elicit weak biological responses before conditioning See figure 4.6 – CS2(light) -> CS1(tone) sequential pairing – CS1(tone) -> US(food) -> CR – Test: CS2(light) -> CR – Note: the Domjan book example of vanilla - cinnamon in food is a confusing example because food can be a US and the flavors are presented simultaneously. This challenges the concept of differential biological strength Biological Strength as a facilitator of performance rather than learning In sensory preconditioning, the initial CS2->CS1 association is “mute” does not produce a response Making the CS1 biologically strong, allows expression of the association with CS2 Not all associations are directly evident in behavior

The Principles of Learning and Behavior, 7e by Michael Domjan Copyright © 2015 Wadsworth Publishing, a division of Cengage Learning. All rights reserved.