The relevance of dissociations and the irrelevance of dissociationism: a reply to Schwartz and Pritchard

Parsing the late positive complex: mental chronometry and the ERP components that inhabit the neighborhood of the P300

Falkenstein, Hohnsbein, and Hoorman (1994) suggested that common measures of P300 latency confound a "P-SR" component whose latency corresponds to stimulus evaluation time and a "P-CR" component whose latency varies with response-selection time, thus casting doubt on work in mental chronometry that relies on P300 latency. We report here a replication and extension of Falkenstein et al. (1994) using a high-density 129-electrode montage with 11 subjects. Spatiotemporal PCA was used to extract the components of the ERP. A centroid measure is also introduced for detecting waveform-timing changes beyond just peak latency. In terms of componentry, we argue that the P-SR and the P-CR, correspond to the P3a/Novelty P3 and the P300, respectively. Conceptually, we dispute the proposed distinction between stimulus evaluation and response selection. We suggest a four-stage ERP model of information processing and place the P3a and the P300 in this framework.

Towards a process paradigm in psychophysiology

This article discusses a theory and method for classifying psychophysiological phenomena as processes prior to considering them as experimental responses. The initial aim then is to construe experimental units as continuous subject-centered processes whose beginning and end depends on the individuals' actions. Boundaries of such processes are systematically defined by first identifying the process as a dimension. Activities are then classified relative to this dimension. Process units are specified by considering two classes of activity which form opposite ends of the dimension of process. The two classes are equivalent in all respects save along the one dimension. These two classes are termed 'pro'- and 'null'-equivalence and are the process methods version of familiar H1 and H0 of hypothetico-deductive procedures. Proportional presence or absence of a parameter value during pro- and null-equivalence of a process is the basis for inferring that a particular measure does or does not typify the process. Actual parameter values of a measure can then form credible limits by which to classify other processes as equivalent or not. These limits can indicate for example whether two experimental effects are dealing with the same or a different process. There are some difficulties in applying this process method, but the general conclusion is that classifying psychophysiological responses at the outset in terms of process clarifies technical and inferential issues in experimentation.