Perceptual learning transfer: Salience of the common element as a factor contributing to the intermixed/blocked effect.

Abstract

Rats received intermixed or blocked preexposure to 2 similar flavor compounds, AX and BX. Following preexposure, conditioning trials took place in which a novel compound stimulus NX was paired with an illness-induced unconditioned stimulus. Animals that were given intermixed preexposure to AX and BX showed lower generalization of the aversive response conditioned to NX to a new compound, ZX, than animals that were given blocked preexposure. The results support the proposal that intermixed preexposure reduces the salience of the common element X to a greater extent than blocked preexposure. The way in which current theories of perceptual learning can predict a differential salience of X after intermixed and blocked preexposure is discussed.

Perceptual learning transfer in an appetitive Pavlovian task

“…Increased attention paid to the unique features A and B could perfectly well account for the intermixed-blocked effect observed in this experiment without having to assume any role for the common element X. Artigas and Prados (2014) hypothesized that a common element X with a reduced salience would acquire less predictive value during the conditioning phase with AX, lowering the generalization (mediated by the common element) of the conditioned response to the BX element. Unfortunately, the contribution of the X element to the standard perceptual learning effect would be masked by the well-established contribution of the increased in salience unique elements A and B: On the one hand, A can be expected to acquire most of the predictive value during conditioning, overshadowing X; on the other hand, the presence of a salient B element would interfere with the retrieval of the conditioned response controlled by the X element at the time of the generalization test with BX (e.g., Artigas, Sansa, Blair, Hall, & Prados, 2006).…”

“…To go round this problem and assess the contribution of the X element to the perceptual learning effect, Artigas and Prados (2014) assessed the transfer of perceptual learning to novel compound stimuli sharing the X element in the absence of A and B. As previously described, they found, using a flavor aversion preparation that intermixed preexposure to AX and BX increased the discriminability of two novel compound stimuli, NX and ZX.…”

“…In the perceptual learning transfer test, N and Z are novel stimuli, identical for all the animals; therefore, the differences observed between the groups given intermixed and blocked preexposure should be attributed to the differential salience of the common element, X. Artigas and Prados (2014) suggested that the best way to account for the perceptual learning transfer, on the one hand, and the reduced conditioning of the X element observed by Mondragon and Murphy (2010;Mondragon & Hall, 2002), on the other, is by reference to the different representations that might arise from intermixed and blocked preexposure to AX and BX: elemental in the case of intermixed and configural in the case of blocked preexposure. The hypothesis is based upon the principles of the stimulus sample theory (Atkinson & Estes, 1963;Estes, 1959;McLaren & Mackintosh, 2000), which presume stimuli to be formed by elements that are sampled in every presentation.…”

“…However, assuming the existence of a second mechanism, reduced salience of X in the intermixed procedure, would extend the facilitatory effect of preexposure to similar compound stimuli containing new unique features (like NX and ZX, for example). Artigas and Prados (2014) recently reported some evidence for such a perceptual learning transfer effect using a flavor discrimination task. After receiving intermixed or blocked preexposure to AX and BX, rats were given conditioning trials with a novel compound stimulus, NX.…”

“…The aim of Experiment 1 was to obtain a double replica of this result by using a set of stimuli that were intended to be identical to those used by Mondragon and Murphy, as well as with a new set of stimuli. These two sets of stimuli were then used to explore the perceptual learning transfer effect reported by Artigas and Prados (2014) in a flavor aversion procedure using a more orthodox appetitive procedure.…”