Classical conditioning

Learning a relation between a cue and an outcome. Prediction-error models explain why a new cue may acquire little value when an established cue already predicts the outcome, the phenomenon of blocking.

Acquisition of a response through observing another individual's reaction to a stimulus. The recipient's later behavior can be tested without the demonstrator present, distinguishing learning from an immediate reaction to the demonstrator.

Transfer of a learned response to stimuli differing from the original cue. Similarity and context determine what is being generalised; a response to a reminder does not require literal identity with the original stimulus.

A model associated with Allan R. Wagner in which stimulus elements occupy an inactive state $I$, primary activation $A_1$, or secondary activation $A_2$. External presentation recruits inactive elements into $A_1$; activity then passes through $A_2$ to inactivity. Learned associates can recruit elements into $A_2$. These are functional states, not established neuronal or receptor identities.

Represent a three-state probability distribution by occupancy fractions $\mathbf{p}=(p_I,p_1,p_2)$ in $I,A_1,A_2$. A nonnegative transfer $f_{ij}\le p_i$ subtracts the same amount from donor $i$ that it adds to recipient $j$. The total therefore remains $p_I+p_1+p_2=1$. If all simultaneous outflows from a state sum to at most its old occupancy, each occupancy remains nonnegative. This elementary conservation argument makes a proposed numerical realization checkable; it does not identify the states with biological compartments.

A development of the model by Allan R. Wagner and Susan E. Brandon distinguishing sensory-specific and emotive components of outcome representations, with potentially different activation time courses and response consequences. It allows one cue to influence multiple response systems differently without requiring contradictory values in one undifferentiated representation.

An extension allowing association changes involving associatively activated, physically absent cues. In the common symmetric formulation, matched $A_1/A_1$ and $A_2/A_2$ states support excitation, while mismatched $A_1/A_2$ and $A_2/A_1$ states support inhibition. The extra rules allow forms of retrospective revaluation; neural reactivation alone does not verify their signs.

A change in responding to an absent target cue after new experience with its previously associated cues. It constrains accounts that permit changes only when the target is physically present.

Training a relation between initially neutral cues before giving one cue biological significance. Responding to the other cue can then depend on inference through the learned structure rather than direct cue–outcome reinforcement.

Reduced learning about an added cue when another cue already predicts the outcome. Control conditions must match exposure and outcome history; blocking in learning is distinct from blocking in experimental design.

Learning through which a cue signals an outcome’s absence or reduction relative to expectation. Summation and retardation tests can help distinguish inhibition from simple low excitatory strength.

Retarded conditioning to a previously nonreinforced cue relative to an appropriately matched novel cue. Changes in attention, retrieval and context can contribute, so it is not uniquely diagnostic of one mechanism.

A response expressed to a cue after learning. It need not be a literal copy of the response directly elicited by the outcome.

An outcome that can elicit a response without the particular cue–outcome learning under study. The term does not imply that every property of the response is immune to previous experience.

A cue whose relation to another event is learned in a conditioning procedure.

Learning through which a cue associated with an aversive event later evokes measured defensive responses. The learned response, the aversive event and subjective experience must be distinguished.

Enhancement of the acoustic startle reflex in the presence of a cue associated with threat. It operationalizes a defensive response rather than directly reading subjective fear.

A defensive response learned through a relation between a cue and an aversive outcome. Laboratory cue responses and the complex fears involved in a clinical anxiety disorder require an explicit translational bridge.

Learning during presentations of a previously predictive cue without the expected outcome. Reduced responding need not mean that the original association has been erased. Context, delay and subsequent experience can alter which association is retrieved.

Retrieval of learning established during extinction, often tested after a delay. Successful immediate extinction need not guarantee later retrieval under different temporal or contextual conditions.^[ref]

Recovery of a conditioned response when the context differs from the context of extinction. It shows that performance after extinction can depend on retrieval conditions.

Pattwell and colleagues compared conditioned responding and extinction across human developmental groups, with parallel mouse investigations. Skin-conductance responses indexed human fear learning. The developmental laboratory pattern motivates clinical hypotheses but does not directly estimate the efficacy of exposure therapy for adolescents.^[ref]

Reappearance of fear after it has decreased. It can reflect a change in retrieval conditions without implying that no useful learning occurred during treatment.

Return of conditioned responding when testing occurs in a context different from the extinction context. It motivates tests of generalisation beyond the treatment setting.