Abstract
One of the most frequent assessments of the relationship between perceptual and motor processing consists in comparing their latencies as derived from Temporal Order Judgments (TOJ) and simple Response Times (RT), respectively. Most of these studies have yielded significant differences between these latencies and concluded in favor of at least a partial perceptual-motor dissociation. The comparison of these latencies remains debatable as the two tasks make use of dual (TOJ) and single (RT) stimulations, possibly entailing cognitive and sensory confounds. As an example of the latter, the rapid sequential stimulation in TOJ may yield the transient fading of the lower saliency stimulus and/or apparent motion. To avoid such hitches, we've replaced the TOJ with an anticipatory RT (ART) task based on the rationale that, like TOJ, ART mirrors the time needed by the internal response to reach a decision threshold and decreases with stimulus saliency. In randomly interleaved blocks of 50 trials (repeated twice), 7 Observers pressed a key either in synchrony with the third of a sequence of three equal contrast (not offset) stimuli appearing at a constant pace of 500 ms (ART), or in response to the onset of the last stimulus presented at a random interval (RT). Each block was also specified by one of four contrasts ranging between .1 and .8. Linear regressions on the ART-RT means and on their variances yield slopes below 1 (.85 and .3, respectively) supporting the notion that perceptual and motor decisions operate on the same internal signal but are based on distinct criteria with the perceptual criterion below the motor one. Relatively to RT, ART yield a significantly smaller variance than TOJ. This higher reliability together with it being more tractable and less time consuming than TOJ favor ART over TOJ as a better task for the assessment of perceptual latencies.