One of the earliest attempts to make psychology scientific was based on the premise that mental activity is made up of a set of simple, elementary processes, just as the enormous variety of chemical compounds are composed from relatively few distinct chemical elements. In the last 100 years, this approach has been most successful in the study of “cognitive” processes, including recognising, remembering, reading, decision-making, and motor-control.
Professor Miller’s primary research interest is to characterise the time course of these processes when we carry out simple perceptual and decision-making tasks. In particular, he would like to find out in which cases the different mental processes operate in strict sequence, with each finishing before the next begins, and in which cases they operate in parallel (at least partly at the same time). This issue is important on theoretical grounds (what are the temporal relationships among the mental processing carrying out distinct information processing aspects of a task?), methodological grounds (what does a reaction time measurement reflect?), and applied grounds (how can we maximise performance by capitalising on the brain’s capacity to perform multiple operations in parallel?). To find out, he studies both behaviour (response time and accuracy) and psycho-physiological responses (EEG, EMG, response force). A variety of evidence already collected suggests that the answer is very complex: that processes operate sometimes in strict succession and sometimes in parallel.
Three secondary research questions have emerged from the above questions about the time course of information processing. First, does attention influence the various elementary mental processes themselves, or the overall time course of processing (serial versus parallel), and if so, by what mechanisms and in what manner? Second, how can the time course of processing best be described by formal mathematical models? Third, how should the statistical analysis of reaction time data be modified in the light of what we are now discovering about the sometimes sequential, sometimes parallel, arrangements of different mental processes?