Sub-sampling of cues in associative learning

Abstract

AbstractTheories of learning distinguish between elemental and configural stimulus processing depending on whether stimuli are processed independently or as whole configurations. Evidence for elemental processing comes from findings of summation in animals where a compound of two dissimilar stimuli is deemed to be more predictive than each stimulus alone, whereas configural processing is supported by experiments employing similar stimuli that fail to find summation. However, in humans the summation effect is robust and impervious to similarity manipulations. In three experiments in human causal learning, we show that summation can be obliterated when partially reinforced cues are added to the summands in training and test (AXY+, BXY+, CXY-, DXY-; test with ABX and ABY). This lack of summation only holds when the partially reinforced cues are similar to the reinforced cues (Experiment 1) and seems to depend on participants sampling only the most salient cue in each trial (Experiments 2a and 2b). We propose a limited-sampling model that captures the present results and others from the animal literature where complex visual stimuli are employed and which have been usually interpreted as evidence in support of configural processing.