Sequence Effects in Simple Cognitive Tasks: the Multiple-weighting-systems Hypothesis

What we did recently influences our current behavior substantially. For example, responses are speeded if observers are to discriminate an item based on its color twice (e.g., color – color discrimination in trials n-1 and n, respectively) compared to when the taskrelevant dimension changes across trials (e.g., orientation – color discrimination). The dimension repetition effect (or DRE) was explained in two mutually exclusive ways: (i) selection-based approach assumes that DREs are a consequence of visual selection processes, while (ii) response-based approach claims these effects to originate from the later processes of response selection. Importantly, neither of the accounts can fully explain available findings on DREs: (i) selection-based approach cannot explain strong DREs observed when visual selection is very easy and fast, while (ii) response-based account cannot explain strong DREs in paradigms where the sequence of perceptual dimensions is response-irrelevant. In my work, I focused on developing a theoretical framework which should account for all the available data by assuming existence of different dimension-sensitive mechanisms that affect different processing stages (visual selection, perceptual analysis). Additionally, a novel paradigm was developed in which two tasks, for which DREs were previously reported, alternated randomly across trials. Across two consecutive trials, the task could either repeat or change. Independently of the task sequence, the task-relevant dimension could either change or repeat. Different experiments used different tasks, that could, on the Multiple-WeightingSystems (or MSW) hypothesis, engage either the same (e.g., both tasks engaged the visual selection mechanism) or different DRE mechanisms. Behavioral and electrophysiological data showed: (i) significant DREs across task changes when the two tasks engaged the same hypothesized mechanism, (ii) no DREs across task changes when the tasks engaged different systems. Overall, the data support the MWS hypothesis, in contrast to the single-mechanism