Michele Scaltritti, principal investigator of the research project 79/20 - Redefining the boundaries between cognition and action through the psychophysiological investigation of binary decisions, supported by the BIAL Foundation, published in the Journal of Experimental Psychology: Human Perception and Performance the article Redefining the Decisional Components of Motor Responses: Evidence From Lexical and Object Decision Tasks. The research team aimed to evaluate whether motor-response execution is or is not part of the decisional process. They have exploited the electromyographic (EMG) signal to partition the reaction time (RT) into a premotor time (PMT), capturing the time from stimulus onset until the onset of the EMG activity, and a motor time (MT), reflecting the time from the onset of the EMG burst until the button press, to assess whether decision processes terminate before response initiation or, instead, whether they are still at play during motor-response execution. The results supported the latter perspective, that is, motor-response execution is not segregated from ongoing decisional dynamics.
ABSTRACT
Models of decision making focusing on two-alternative choices have classically described motor-response execution as a nondecisional stage that serially follows the termination of decision processes. Recent evidence, however, points toward a more continuous transition between decision and motor processes. We investigated this transition in two lexical decisions and one object decision task. By recording the electromyographic (EMG) signal associated with the muscle responsible for the manual responses (i.e., button press), we partitioned single-trial reaction times into premotor (the time elapsing from stimulus onset until the onset of the EMG burst) and motor times (the time elapsing from the onset of the EMG burst and the button press), with the latter measuring response execution. Responses were slower for pseudowords and pseudo-objects compared to words and real objects. Importantly, these effects were reliable even at the level of motor time measures. Differently, despite the reliable effect at the level of reaction times and premotor times, there was no difference in motor times between high- and low-frequency words. Although these results, in line with recent evidence, challenge a purely noncognitive characterization of motor-response execution, they further suggest that motor times may selectively capture specific decisional components, which we identify with late-occurring verification and/or control mechanisms.
