In relation to psychology to pair by association is the action of associating a stimulus with an arbitrary idea or object, to elicit a response, usually emotional. This is done by repeatedly pairing the stimulus with the arbitrary object.
For example, repeatedly pairing images of beautiful women in bathing suits, elicits a sexual response in most men. Advertising agencies, for example, repeatedly pair products with attractive women in television commercials. This is with the intention of eliciting an emotional or sexually aroused response in the consumer.
This causes the consumer to be more likely to buy the product than when presented with a similar but competing product without such an association.
Behaviorists will often use paired association tests to determine the strength of verbal behavior, in particular, B.F Skinner's concept of the verbal response class called intraverbals.[1]