Extending continuous flow models of immediate decision reports to delayed decision reports

Continuous flow and evidence accumulation models have recently been combined to provide an integrated account of decision and motor mechanisms engaged in choice reaction time tasks. According to this account, muscle activation is essentially determined by the evidence accumulation decision variable through a continuous decision-to-motor transmission of information. However, it remains unclear whether and how this framework can be extended to situations that impose a time lag between the commitment to a choice and the expression of that choice through actions. Such situations have been studied using response signal (RS) decision tasks featuring a short delay between the offset of the stimulus and a signal to respond. The present work integrates recent developments in decision-making, working memory, and motor control research to extend models of immediate decision reports to delayed decision reports. We assumed that the evidence accumulation decision variable transitions to sustained activity after hitting a threshold to achieve the short-term maintenance of the selected choice. The level of sustained activity then constitutes the starting point for a second phase of accumulation, in which subjects sample evidence from the RS to activate the muscles. We tested predictions from the theory at the behavioral and muscle activation levels in three RS decision tasks featuring manipulations of stimulus duration, delay duration, and foreknowledge of the stimulus-response mapping. Muscle activation was measured using electromyography. The theory provided a unified account of empirical effects.