Fractionning Reaction Time to probe the validity of the Drift Diffusion Model parameters

  • Weindel Gabriel
  • Anders Royce
  • Alario F.-Xavier
  • Burle Boris

  • Pre-motor time
  • Electro-myography
  • Decision making
  • Drift Diffusion Model
  • Speed Accuracy trade-off
  • Non-decision time
  • Motor time


We designed a two-alternative forced choice experiment in which the by-trial reaction times could be fraction-ated into pre-motor (PMT) and motor times (MT), based on the onset of muscular activity from the electromyo-graphic (EMG) recordings (Figure 2c). We then compared this empirical decomposition to the decomposition performed by the Drift Diffusion Model (DDM, Ratcliff, 1978). Using these two decompositions, we show that the non-decision time parameter of the DDM is highly correlated with the Motor Time that was recorded when the participants stressed Accuracy over Speed. Furthermore, we show that fitting the by-trial Pre-Motor Time with the DDM mainly modulated the non-decision time parameters. The relative contribution of decision time and motor time components in the overall Reaction Time (based on speed versus accuracy instructions) was observed. Correlation analyses between speed instructions on empirical data suggest that their could be a change in the architecture of cognitive processes rather than a quantitative change between Speed-Accuracy tradeoff (SAT) levels.