Using reaching trajectories to reveal the dynamics of stimulus categorisation

In categorisation tasks, such as lexical decision, the standard dependent measure in cognitive psychology is mean reaction time (RT). While mean RTs are certainly informative, they are relatively insensitive to the dynamics of the categorisation process under investigation. To address this, some researchers have begun using reaching trajectories as their dependent measure. The promise of this continuous measure is that it can reveal effects while stimulus processing is still unfolding. In this talk I will discuss a series of experiments in which we use reaching trajectories to investigate the effects of spatial and temporal attention in two different categorisation tasks: lexical decision and face (male/female) categorisation. Replicating earlier work, our results indicate strong modulatory effects of attention on stimulus categorisation. Looking at the time course of these modulatory effects, we see that they arise very early (~200 ms) and that they are remarkably short-lived.