Table 1.

Definitions of specialized psychological and behavioral terms.

Term	Definition
Acquisition of a new instrumental response for conditioned reinforcement (ANR)	Behavioral procedure used to study appetitive conditioned reinforcement. Animals are presented with a CS (e.g. a tone) that is paired with an appetitive reinforcer (e.g. food) during pavlovian conditioning. The manipulandum for a new instrumental response (e.g. a lever) is then presented to the animal. Responding on one of the levers produces the CS; the other control lever has no consequence. If the CS is a conditioned reinforcer then it should support the acquisition of a new response even when the primary reinforcer (i.e. the food) is no longer presented.
Active avoidance	Behavioral procedure in which animals are trained to make an instrumental response in the presence of a discrete CS or context in order to avoid the presentation of an aversive reinforcer (e.g. an electric footshock). This procedure can be contrasted with “passive avoidance,” in which animals are required to remain where they are in order to avoid electric shock.
Autoshaping	Behavioral procedure used to study conditioned approach or appetitive conditioned direction. Animals are trained to associate a readily-localizable CS (e.g. a light-lever combination) with the presentation of an appetitive reinforcer through pavlovian conditioning. During training, the CS comes to elicit approach responses that may be directed towards the CS itself (termed sign-tracking) or towards the location in which the reinforcer is delivered (termed goal-tracking). Often a control CS, not associated with a reinforcer, is included in the procedure, and animals are considered to have acquired the association when they approach more during presentation of the reinforcer-associated CS than during the control CS.
Avoidance	An instrumentally conditioned action that prevents an aversive reinforcer from occurring.
Conditioned approach	The psychological process by which a CS acquires reinforcing properties that promote approach towards it; often the CS will also elicit responses that are appropriate to the reinforcer (e.g. a rat will lick a CS associated with a liquid reinforcer).
Conditioned direction	Our suggested term to encompass both conditioned approach and avoidance, since both processes depend upon the same neural circuitry and the CS performs the same directing function in both processes.
Conditioned freezing	The rodent-specific fear response of the cessation of all movement, except for respiration, in the presence of a fear-eliciting stimulus.
Conditioned inhibitor	A CS that suppresses or reduces the number or size of conditioned response that would be elicited by presentation of another CS. Conditioned inhibition is usually measured through “summation” tests (in which the excitor and inhibitor CS are presented simultaneously, and levels of responding compared to the presentation of the excitor CS alone) and in “retardation of acquisition” tests, in which the conditioned inhibitor is associated with another outcome, which produces delayed learning compared to control CSs that have not previously been trained as conditioned inhibitors.
Conditioned motivation	The psychological process by which a pavlovian CS affects levels of instrumental responding. This term is often used synonymously with pavlovian-instrumental transfer, but we suggest that this term should be used more generally to refer to both pavlovian-instrumental transfer and conditioned suppression.
Conditioned reinforcement	The psychological process by which a pavlovian CS acquires conditioned, or secondary, reinforcing properties that allow it to support instrumental responding (e.g. as measured using the ANR procedure). This term is often used to refer to the appetitive conditioned reinforcing properties of a CS, but we suggest that it should also refer to conditioned punishment, as both processes depend upon the same neural circuitry, and the CS is presented following the response, either as a positive reinforcer in appetitive conditioned reinforcement or as a negative reinforcer in conditioned punishment.
Conditioned punishment	The psychological process by which a pavlovian CS acquires conditioned, or secondary, aversive reinforcing properties (i.e. the stimulus becomes feared) such that it promotes avoidance of a particular instrumental response. We suggest that as conditioned punishment depends upon the same neural circuitry as appetitive conditioned reinforcement, that it is more parsimonious to term conditioned punishment “aversive conditioned reinforcement.”
CS-specific properties of an association	The sensory-specific properties of a pavlovian CS—for example, a specific frequency of tone or light—associated to a specific outcome or pavlovian US. The association of the sensory-specific properties of a pavlovian CS is hypothesized to depend upon the basolateral amygdala.
Conditioned stimulus	In pavlovian conditioning, a previously motivationally neutral stimulus that is associated with an unconditioned stimulus (reward or reinforcer).
Conditioned suppression	The capacity of an aversive pavlovian CS to suppress ongoing instrumental responding.
Devaluation	The reduction in value of a reinforcer by either associating the reinforcer with an unpleasant outcome (e.g. gastric malaise induced by lithium chloride injection for food reinforcers) or by reducing the motivation for the reinforcer (e.g. by allowing free access to the reinforcer prior to testing, as in sensory-specific satiety procedures).
Extinction	The process by which the response to a previously learned association (pavlovian or instrumental) is reduced. Procedurally, pavlovian extinction occurs through presentation of the CS without the US, and instrumental extinction occurs by omitting reinforcement following the previously-reinforced response. Importantly, extinction is not “unlearning” of the previously learned association, but instead reflects the formation of a new, inhibitory “CS-no US” or “action-no outcome” memory that inhibits the original memory in a context-specific manner.
Fear-potentiated startle	The increase in startle response produced by a stimulus (e.g. a loud noise) when it is presented in the presence of a fear-eliciting stimulus or an anxiogenic environment.
General properties of an association	The generalized motivational properties of a pavlovian association—for example, the association between a pavlovian CS and an appetitive motivational outcome, though not necessarily the association between the CS and a specific outcome. The encoding of the generalized properties of an association is hypothesized to depend upon the central nucleus of the amygdala.
General PIT	In pavlovian-instrumental transfer, the process by which any appetitive CS can enhance instrumental responding for an appetitive reinforcer (cf. specific PIT).
Goal-directed	In instrumental conditioning, the association by which an action that produces a particular outcome (or goal state) is represented. Responses are elicited depending upon the representation of the outcome, so that if the outcome is devalued then the action will not be elicited.
Goal-tracking	Conditioned approach towards the location in which the reinforcer is delivered when a pavlovian CS, associated with an appetitive reinforcer, is presented.
Instrumental conditioning	A type of learning in which the outcome is dependent upon the behavior of the individual. Learning can occur through positive reinforcement (increasing the number of responses that produce an appetitive reinforcer), negative reinforcement (increasing the number of responses that allow the individual to avoid an aversive reinforcer) or punishment (decreasing the number of responses that produce an aversive reinforcer).
Negative reinforcement	A type of instrumental conditioning procedure in which a particular behavior is increased in frequency due to the avoidance of an aversive outcome.
Pavlovian conditioning	A type of learning in which a previously motivationally neutral stimulus is paired in space and time with a motivationally relevant unconditioned stimulus. The behavior of the individual does not affect the contingency between the presentation of the two stimuli.
Pavlovian-instrumental transfer (PIT)	The behavioral procedure with which appetitive conditioned motivation can be assessed. Animals are trained separately on an instrumental association and a pavlovian association for the same reinforcer. Responses made in the presence of the pavlovian CS can be taken as a direct test of conditioned motivational properties of the CS (without the CS acting to induce retrieval of the instrumental action representation).
Pearce-Hall model of learning	A model of pavlovian conditioning which predicts that individuals pay greater attention to events that are surprising, which facilitates learning.
Prediction error	During a behavioral experience, the mismatch between what is expected based on prior experience and what actually occurs. Prediction error is hypothesized to drive learning in many theories, including the Rescorla–Wagner model of learning. Neurobiologically, prediction error correlates with levels of midbrain dopamine signaling.
Rescorla–Wagner model of learning	A model of pavlovian conditioning in which individuals are hypothesized to learn about the association between pavlovian CSs and USs based on prediction error (i.e. learning occurs when there is a mismatch between the prediction of, and the actual delivery, of the US). Changes in the prediction of likelihood (“associative strength,” ΔVx) are determined by the salience of the CS (α), the ease of learning about the CS (β) and the degree of learning about the US that has already occurred (i.e. the difference between the total amount of learning that could theoretically occur about the CS, λ, and what has been learned so far, Vtot). This is represented by the Rescorla–Wagner equation, ΔVx = αβ(λ – Vtot).
Safety signal	A pavlovian CS which, when presented, indicates that an aversive reinforcer will not be delivered.
Second-order schedule	Behavioral procedure often used to measure the conditioned reinforcing properties of a CS. Under a second-order schedule, animals are trained to associate an instrumental response with both an appetitive reinforcer and a pavlovian CS. During training, the response requirements are increased such that a certain number of responses will produce the CS, and a certain number of CSs, or responses within a certain period of time, will produce the reinforcer.
Sign-tracking	Conditioned approach towards the location of a pavlovian CS when the CS, associated with an appetitive reinforcer, is presented.
Specific PIT	In pavlovian-instrumental transfer, the process by which a CS associated with a specific appetitive reinforcer can enhance instrumental responding for the same reinforcer.
Stimulus-response	In instrumental conditioning, the association by which a pavlovian CS elicits a response, which is independent of the representation of the outcome. If responding is habitual (stimulus-response) then it will be maintained even if the outcome of the action has been devalued. Stimulus-response learning typically occurs following overtraining, or training in which the contingency between the response and the outcome is degraded (e.g. interval schedules).
Stimulus saliency	The capacity of a stimulus to direct attention. This could be due to the physical attributes of the stimulus (e.g. intensity) but is often also related to the motivational relevance of a CS.
Unconditioned stimulus	In pavlovian conditioning, a stimulus that is motivationally relevant to the individual (e.g. food, water, sex).

Each term is italicized in the text at its first appearance.