Latent inhibition and learned irrelevance in human contingency learning

Abstract

Introduction To say that latent inhibition (LI) is a well-established phenomenon of animal conditioning is a serious understatement. Since its first demonstration 50 years ago, the finding of a retardation in conditioning following nonreinforced preexposure to a stimulus has been reported countless times across species from sheep to snails, and from goats to goldfish. Given the ubiquity of LI in animal conditioning, and the suggestion that, under some circumstances at least, a common associative mechanism might also underlie human contingency learning (the acquisition of knowledge about the predictive relationship between a cue and an outcome; Dickinson, Shanks, & Evenden,1984), we might expect a search of the contingency learning literature to reveal many demonstrations of LI in humans. The conclusions to be drawn from such a search depend largely on whether an empirical or theoretical approach to LI is taken. An empirical approach to LI If we define LI empirically, as the experimental observation of a retardation in the development of conditioned responding to a stimulus resulting from nonreinforced preexposure to that stimulus, then we must conclude that LI has been demonstrated many times in human contingency learning (e.g. De la Casa, Ruiz, & Lubow, 1993b; Ginton, Urca, & Lubow, 1975; Gray, N.S., et al ., 2001; Lubow, Ingberg-Sachs, Zalstein-Orda, & Gewirtz, 1992). For example, during Ginton et al .'s preexposure phase, participants were required to report the number of repetitions of a list of nonsense-syllables (a masking task; see below). The to-be-conditioned stimulus (CS), a burst of noise, was interspersed throughout presentation of this list.