Simultaneous pairing increases evaluative conditioning: Evidence for the role of temporal overlap but not of onset synchrony

Evaluative conditioning (EC), a change in valence of a stimulus due to its co-occurrences with other stimuli, is frequently used to study attitude formation. The present studies investigate whether EC is influenced by whether the co-occurring stimuli have their onset at the same (vs. different) time, i.e., their onset (a)synchrony. To this end, we introduce a novel and sensitive measure which tests EC effects immediately after their assumed origin, i.e., after the co-occurrence of two stimuli in the conditioning phase. A pretest supported the validity of this measure. Study 1 showed that EC effects assessed during conditioning were smaller when paired stimuli had asynchronous onsets and a smaller temporal overlap. Yet, onset synchrony did not affect EC effects in Study 2 when temporal overlap of stimuli was held constant. Together these results suggest that EC is not affected by stimulus onset synchrony but might be affected by the amount of temporal overlap of the paired stimuli. Neither study showed effects of these pairing manipulations on EC effects assessed after the conditioning phase. Still, EC effects observed during conditioning strongly predicted EC effects observed after conditioning. Together our studies establish the new online measure and its usefulness in investigating theoretical questions of EC. Our findings extend previous research on the benefits of temporal contiguity of stimulus co-occurrences and provide new insight into the relation of post-conditioning EC and single stimulus co-occurrences during the conditioning phase.