Pavlovian and Instrumental Conditioning: Key Concepts, Sign/Goal Tracking, CTA, Eye Blink, and Modulators
Pavlovian Conditioning: Core Concepts, Variations, and Modulators
Core idea: a neutral stimulus (CS) becomes predictive of a biologically relevant outcome (US) and elicits conditioned responses (CR) that anticipate the US.
Distinguish between approach to the US (goal tracking) and approach to the predictor (sign tracking). The transcript emphasizes that learning can manifest as various conditioned approaches, not just one fixed form.
Approach, Sign Tracking, and Goal Tracking
Approach as a reflexive response reflecting the prediction of the US (the thing the organism wants).
Example: salivation as a general indicator of wanting; approach toward the food port when a CS predicts sucrose.
Case: chamber with sucrose in a food port; a CS (e.g., white noise) predicts sucrose, leading to increased approach toward the port following CS onset.
Dinner-bell analogy: a neutral cue (bell) predicts food; people run downstairs because the bell has become predictive of food.
Quail experiment (sex paradigm): a light (CS) becomes predictive of mate access (US). When the light turns on, the door opens soon after, and the quail approaches the door.
Basic learning outcome: the CS predicts the US, so the organism approaches the place/CS in anticipation of the US.
Two major strategy ends on a spectrum:
Goal tracking: approach the US itself (e.g., approach the food location or the mate).
Sign tracking (auto-shaping): approach the CS itself as if it were the US; the CS acquires incentive properties.
Terms to know (synonyms): sign tracking = auto-shaping; goal tracking = approach to the US.
Individual variation: within a species, some individuals consistently show sign-tracking, others show goal-tracking, and some show a mix.
Sign-tracking in pigeons: a tangible CS (a light) becomes predictive of food; some pigeons peck at the light as if it were food, and, after a CS → US reassignment (light predicting water), they continue sign-tracking as if the CS is the reward (pecking at the light as if drinking).
Lever-based examples: some rats that track the CS (lever) will engage with the lever itself (nibbling, biting) rather than only approaching the food; goal trackers go to the food site.
Practical takeaway: You cannot a priori predict whether a conditioned response will be sign-tracking or goal-tracking; responses are partly determined by the organism, the CS, and the context.
Relevance to human behavior and addiction: many addicts exhibit sign-tracking tendencies, focusing on cues/rituals (needle, spoon, tubing) that predict drug delivery, sometimes more than the actual drug itself.
Important caveat: variability exists across species and individuals; some show robust sign-tracking, others strong goal-tracking, and many show intermediate patterns.
Sign Tracking, Goal Tracking, and Cross-Species Evidence
Sign-tracking observed across multiple species (rats, pigeons, etc.) and various CS modalities (light, tone, lever).
Studies show that sign tracking can involve direct interaction with the CS (e.g., pecking a light or nibbling a lever) as if the CS were the US.
When CS → US associations are reversed (e.g., light predicting water instead of food), sidetracking can persist, illustrating the CS’s acquired incentive salience.
Classic sidetrack example in pigeons: some pigeons peck at a predictive light as if it were food; after CS→shock pairings, changes in the CS’s predicted outcome shift the behavior (pecking to “drink” the light when CS predicts water).
Animal sex-lab anecdote (rat example with a pine pylon): male rats show sidetracking by vigorously pursuing the CS (pylon) that predicts mating availability.
Sign-tracking vs. goal-tracking has practical implications for interpreting conditioned responses and for understanding individual differences in learning and addiction.
Instrumental Conditioning and Pavlovian–Instrumental Interactions
Instrumental (operant) conditioning basics: lever pressing to obtain a food reward.
In Pavlovian–instrumental transfer (PIT) experiments, a Pavlovian CS can modulate instrumental behavior (e.g., lever pressing) even when the CS itself is not delivering the US.
In fear conditioning and aversive PIT: a CS may predict an aversive US (shock), and during CS presentations, animals may suppress instrumental responding (fear-induced inhibition).
Suppression ratio as a fear index in PIT contexts:
Definition: the amount of instrumental responding during the CS relative to responding during a baseline/no-CS or total session.
Common formulation:
SR= rac{P{CS}}{P{CS}+P_{NoCS}}Here, P{CS} is the number of instrumental responses (e.g., lever presses) during the CS, and P{NoCS} (or the non-CS period) is the number of responses when the CS is absent.
Interpretation: As fear learning increases, lever pressing during the CS decreases, driving the suppression ratio toward 0. In the absence of fear, the ratio approaches 0.5 (no CS effect).
Phase structure in Pavlovian–instrumental protocols (example given in the transcript):
Phase 1 (Instrumental): animals learn to press a lever to obtain food (establish baseline instrumental responding).
Phase 2 (Pavlovian conditioning): a CS (tone or light) becomes predictive of an aversive US (shock).
Phase 3 (PIT test): CS is presented while the animal has access to the lever; the test measures how the CS modulates lever pressing in the absence/presence of the US.
Key observation: during CS presence, fear responses suppress lever pressing; during CS absence, lever pressing returns to baseline levels.
Distinction: this is an instrumental/operant phase (Phase 1) plus a Pavlovian phase (Phase 2) and a test phase (Phase 3) to examine interactions between the two systems.
Conditioned Suppression and Fear Learning
Suppression learning as a proxy for fear: lever pressing decreases when the CS predicts an aversive outcome.
Interpretation: suppression indicates that the organism anticipates the US and alters behavior accordingly to avoid the unpleasant outcome.
Aversive conditioning basics: conditioning can occur with neutral stimuli paired with aversive US (e.g., shock or odor with shock).
Counterbalancing and design notes (brief): studies are typically counterbalanced and/or reversed to control for order effects.
Conditioned Taste Aversion (CTA)
CTA is a robust form of Pavlovian conditioning where a flavor (CS) predicts sickness (US) and leads to avoidance of that flavor.
Classic Smith & Rawl (1967) style CTA design:
Control group: one exposure to a palatable flavor (e.g., juice) followed by a normal return to water; rats drink juice about 80% of the time.
Experimental group: one exposure to the flavor followed by sickness (induced nausea, e.g., X-ray exposure).
Test phase: preference between juice and water after conditioning.
Result: experimental rats avoid the juice (drink far less) compared to controls, even when the sickness occurs hours after tasting the juice.
Key twist: rats cannot vomit; sickness is inferred from avoidance behavior and tasting decisions.
Delay tolerance in CTA: researchers varied the delay between tasting the juice and induction of sickness (0, 1, 3, 6, 12, 24 hours).
Across delays, CTA persisted: rats avoided the juice regardless of delay, including long delays (up to 24 hours).
The long-delay CTA demonstrates the power of CTA to form associations over relatively long time gaps compared to other conditioning paradigms.
Real-world intuition: CTA is a strong adaptive mechanism for avoiding toxins after a single poor experience with a flavor.
Note on interpretation: people commonly relate post-ingestive illness to the flavor experienced hours earlier, illustrating human CTA-like reasoning, though real-world timelines for food poisoning are typically shorter than the longest CTA delays described here.
Mention of a cautionary comment about timing realism (not all sickness is due to a flavor; some explanations are more mundane): CTA emphasizes robust learning when the flavor reliably predicts illness.
Summary: CTA is a powerful example of how one trial can produce long-lasting, adaptive avoidance learning driven by the CS–US link.
Eye Blink Conditioning in Rabbits
Eye-blink conditioning (delay eyeblink conditioning) as an emblematic example of classical conditioning:
UR: reflexive blink to a puff of air.
CS: tone or light paired with the puff of air; after many pairings, the CS alone elicits a CR (anticipatory blink).
Key findings:
The CR (anticipatory blink) develops slowly with many trials and, over time, becomes faster, stronger, and longer in duration as the animal learns to anticipate the puff.
The brain regions generating the CR differ from those generating the UR blink, highlighting distinct neural substrates for anticipatory versus reflexive eye blinking.
Importantly: the CR can be slower to onset, but stronger and longer in duration compared to the UR, reflecting the anticipatory nature of the response.
Conceptual point: the CR does not have to be the same as the UR in timing or form; the CR is an anticipatory response that prepares the organism for the US.
Broader implication: anticipatory responses can involve different behaviors from reflexive responses, including avoidance or other preparatory actions.
Valence, Motivation, and Compensatory Responses
Anticipatory (CR) responses can be compensatory with respect to the US (e.g., drug tolerance):
A-process vs. B-process framework (opponent-process theory): when a drug is taken repeatedly, the body develops compensatory responses to stabilize physiology (e.g., heart rate changes).
If the body anticipates the drug, the physiological response can be attenuated (e.g., heart rate may slow in anticipation of adrenaline surges).
Real-world analogy: caffeine users develop physiological anticipations; if they skip their usual dose, withdrawal symptoms occur due to absence of the predicted stimulant effect.
The central idea: predictive cues can elicit physiological adjustments that buffer the upcoming US, contributing to tolerance and withdrawal phenomena.
Four Key Factors That Influence Pavlovian Conditioning
Number of pairings (frequency): more pairings strengthen the CS–US association.
Intensity/magnitude of CS and US: more salient, meaningful, or intense stimuli yield stronger learning.
Reliability/predictability: the CS–US relationship must be reliable; perfect predictability accelerates learning; partial predictability still supports learning but more slowly.
Example: a tone followed by shock on every trial yields stronger learning than a tone followed by shock on some trials only.
Timing (temporal contiguity): closer timing between CS and US facilitates learning; very long delays weaken learning for shorter-lived species.
Timed contiguity: cognitive systems are better at learning when the CS precedes the US by a short interval; longer delays (especially beyond species-specific limits) hinder learning.
Summary takeaway: stronger, more reliable, timely, and frequent CS–US pairings yield faster and stronger conditioning.
Individual Stimuli: Properties that Shape Conditioning
Initial value of CS and US:
CS should be neutral (initially meaning nothing) or relatively inconsequential to promote learning about the US.
US should be meaningful (salient) to ensure that the CS–US association is worth forming.
Discriminability: how easily the CS and US can be distinguished by the organism; greater discriminability facilitates learning.
Naturalistic relevance and novelty:
Stimuli that are ecologically relevant or naturally paired with the US are learned faster (e.g., dogs learning a bell as a predictor of food more readily than an arbitrary cue).
Novel stimuli (latent inhibition): prior exposure to the CS without the US can slow learning when the CS is later paired with the US (latent inhibition).
CS pre-exposure (latent inhibition): prior exposure to the CS without the US reduces the rate of future learning when the CS later becomes predictive.
US pre-exposure: pre-exposure to the US can reduce the ability to learn a CS predicts that US because the US is already predictable or familiar, reducing attention to the CS.
Belongingness or relevance (Garcia effect): learning is stronger when the CS and US naturally co-occur in a way that makes sense semantically or ecologically.
Garcia, Koelling, and colleagues demonstrated that some CS–US pairings are more readily learned than others due to “belongingness” or relevance (e.g., taste-flavor CS with sickness is especially strong; light/sound CS with shock is strong when ecologically plausible).
Garcia–Koelling (Belongingness) and Related Evidence
Experimental paradigm (Garcia & Koelling style): rats learn to associate flavors with sickness more readily than with other non-flavor CSs; sensory modalities have natural associations (taste with malaise; visual/auditory cues with shock), reflecting ecological validity in learning.
Experimental design (a representative version):
Water-deprived rats are exposed to a flavored water (CS) during drinking in a chamber with an audiovisual context.
After initial exposure, rats are divided into groups that receive sickness (e.g., lithium chloride) or shock as the US, paired with different CS modalities (taste flavor vs. audiovisual cue).
In testing, rats are exposed to the CSs again to observe which CSs elicit avoidance or reduced consumption, indicating which CS–US pairings were learned.
Key findings:
Flavor (taste) CSs robustly predict sickness, leading to conditioned taste aversion (CTA) and reduced intake of the flavored solution when tested.
Audiovisual CSs pair with shock, and they produce avoidance of the aversive context differently than taste-based CSs.
The belongingness principle explains why some CS–US pairings yield stronger learning when the CS naturally relates to the US (taste with sickness; shock with sudden aversive cues).
Practical implication: the ease of learning is not solely determined by generic salience; ecological fit and semantic relevance play crucial roles in Pavlovian conditioning.
Practical and Theoretical Implications
Learning can be adaptive and context-dependent: even a single trial can generate robust learning (CTA) under the right conditions, especially when the US is highly meaningful and the CS provides a clear predictive cue.
Sign-tracking vs. goal-tracking has important implications for understanding individual differences in addiction and cue-reactivity; cues can gain incentive salience and drive behavior independently of the primary reward.
Anticipatory (CR) responses can be functionally different from reflexive (UR) responses and can engage distinct neural circuits and behavioral strategies (e.g., slower, stronger CR in eye-blink conditioning).
The environment and EXOGENOUS factors (such as caffeine, drugs, or other substances) produce anticipatory physiological adjustments; when the environment predicts a substance, the body can compensate to maintain homeostasis, contributing to tolerance and withdrawal phenomena.
Ethical and practical relevance: understanding the mechanisms by which cues provoke craving or avoidance can inform interventions for addiction, phobias, and other conditions that involve conditioned responses to cues.
Quick Reference: Key Terminology
CS: conditioned stimulus; initially neutral cue that predicts the US.
US: unconditioned stimulus; inherently meaningful stimulus that naturally elicits a response.
CR: conditioned response; learned response to the CS that anticipates the US.
UR: unconditioned response; reflexive response to the US.
Sign tracking: approaching the CS itself as if it were the reward.
Goal tracking: approaching the location or outcome (the US) predicted by the CS.
CTA: conditioned taste aversion; learning to avoid a flavor after it predicts illness.
PIT: Pavlovian–instrumental transfer; a Pavlovian CS modulates instrumental responding.
Suppression ratio: a measure of fear or avoidance in a conditioning context, defined as
SR= rac{P{CS}}{P{CS}+P{NoCS}} where P{CS} is the instrumental response during CS and P_{NoCS} is the response when CS is absent.
References to Concepts Mentioned (In-Text Prompts)
Sign-tracking vs. goal-tracking across species (rats, pigeons, quails).
Light-predicts-mate paradigm in quails; CS can become a proximate target of approach.
Pigeons showing CS approach behaviors are examples of CS acquiring incentive value.
Lever-based tests differentiate sign-tracking (CS approach) vs. goal-tracking (US approach).
CTA paradigms with delayed sickness demonstrate long-delay learning advantages for certain CS–US relationships.
Eye-blink conditioning demonstrates distinct neural substrates for CR vs. UR and illustrates how anticipatory responses differ in timing and form from reflexive responses.
Garcia–Koelling experiments illustrate belongingness effects that influence CS–US pairing strength.
Four conditioning modifiers (frequency, intensity, reliability, timing) and several stimulus properties (neutrality, discriminability, novelty, pre-exposure effects) shape learning rates and outcomes.
Endnotes
The material links basic conditioning theory to real-world phenomena (drug cues, cravings, habit currents, and conditioned aversions) and emphasizes the variability across individuals and species.
Chapter and lecture cross-references (e.g., upcoming content on chapter six and lecture six) indicate that this is part of a broader curriculum integrating mathematical aspects of predictability and neurobiological substrates.