Exploring the relationship between response time, sensitivity and bias in categorical and coordinate visuospatial processes: Evidence for hemispheric specialisation

Right visual field-left hemisphere (RVF-LH) and left visual field-right hemisphere (LVF-RH) specialisations found for categorical and coordinate visuospatial judgements, respectively, are thought to demonstrate two different perceptual processes. In the current experiment, we used signal detection theory to investigate categorical and coordinate processes, and to explore the relationship between response time (RT), sensitivity and bias measures. We found a LVF-RH advantage for the processing of categorical spatial relations when this effect was indexed by sensitivity. We also found that task influenced response bias in RVF-LH trials, but not in LVF-RH trials. Increased sensitivity was correlated with faster responses in the coordinate task but slower responses in the categorical task, and faster RTs when responding liberally in RVF-LH but not LVF-RH categorical trials. By analysing signal detection measures alongside RT, the findings suggest that differences in sensitivity and response bias may contribute to typical task by hemisphere effects in RT.