A review on mental imagery in fear conditioning research 100 years since the 'Little Albert' study.

Since the seminal 'Little Albert' study by Watson and Rayner (1920), fear conditioning has become one of the most commonly used paradigms for studying the etiology of anxiety-related disorders. In a fear conditioning procedure, a (neutral) conditioned stimulus (CS) is paired with an aversive unconditioned stimulus (US), resulting in fear-related conditioned responses (CRs) to the CS. Whereas fear conditioning research initially focused on observable elements in the environment (i.e., CSs, USs, and their contingency) and their effects (i.e., CRs), subsequent research indicated that attention should also be given to unobservable mental events (e.g., intrusive memories of aversive outcomes) to more fully account for the symptomatology of anxiety disorders. In this paper, we review the research relating to four major research questions on the relationship between mental imagery and fear conditioning: (1) Can mental imagery substitute for actual stimulus administration? (2) Can mental imagery inflate CRs? (3) Can fear conditioning result in the installment of mental images as CRs (i.e., intrusions)? (4) Can mental imagery-based interventions reduce CRs? For all these research questions, tentative confirmatory evidence has been found and these findings corroborate contemporary conditioning theories. Nonetheless, we point to several open questions and methodological issues that require further research.