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P300 event-related brain potential (ERP) measures are affected by target stimulus probability, the number of nontargets preceding the target in the stimulus sequence structure, and interstimulus interval (ISI). Each of these factors contributes to the target-to-target interval (TTI), which also has been found to affect P300. The present study employed a variant of the oddball paradigm and manipulated the number of preceding nontarget stimuli (0, 1, 2, 3) and ISI (1, 2, 4 s) in order to systematically assess TTI effects on P300 values from auditory and visual stimuli. Number of preceding nontargets generally produced stronger effects than ISI in a manner suggesting that TTI determined P300 measures: Amplitude increased as TTI increased for both auditory and visual stimulus conditions, whereas latency tended to decrease with increased TTI. The finding that TTI is a critical determinant of P300 responsivity is discussed within a resource allocation theoretical framework. Disciplines Arts and Humanities | Life Sciences | Medicine and Health Sciences | Social and Behavioral Sciences Publication DetailsThis article was originally published as Gonsalvez, CJ and Polish, J, P300 amplitude is determined by targetto-target interval, Psychophysiology, 39, 2002, 388-396 AbstractP300 event-related brain potential~ERP! measures are affected by target stimulus probability, the number of nontargets preceding the target in the stimulus sequence structure, and interstimulus interval~ISI!. Each of these factors contributes to the target-to-target interval~TTI!, which also has been found to affect P300. The present study employed a variant of the oddball paradigm and manipulated the number of preceding nontarget stimuli~0, 1, 2, 3! and ISI~1, 2, 4 s! in order to systematically assess TTI effects on P300 values from auditory and visual stimuli. Number of preceding nontargets generally produced stronger effects than ISI in a manner suggesting that TTI determined P300 measures: Amplitude increased as TTI increased for both auditory and visual stimulus conditions, whereas latency tended to decrease with increased TTI. The finding that TTI is a critical determinant of P300 responsivity is discussed within a resource allocation theoretical framework.

Emotional Stroop tasks have gained wide interest in scientific literature in the last two decades. Although no direct measure of attention is employed, these studies infer the presence of preferential processing of threatening information based on reaction time (RT) impairment in a competing task. Because event-related potential (ERP) measures are sensitive to both the extent (amplitude) and speed (latency) of cerebral processing, they are valuable tools with which to examine more directly the claim that threatening stimuli are associated with enhanced attention. Twenty-two students rated a pool of words to identify those that were personally disturbing. Two word types (threat and neutral) were then compared in two tasks (color relevant, in which the color ink of words was identified, and word relevant in which words were classified as threatening or not). No emotional Stroop effect was observed in terms of longer RTs to identify the colors of threat words. ERP results provided valuable information about threat processing which was not observed with behavioral measures. Threat content was associated with larger P2 amplitude in the right than left hemisphere, and larger P3 amplitude, across tasks. The results indicate strong evidence for enhanced processing of threat-related stimuli in healthy individuals. It is concluded that ERPs are a sensitive measure of processes underlying emotional Stroop performance, which can be used to elucidate attentional biases in healthy and clinical populations.

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This study draws attention to the very real possibility that supervisors' assessments are not as reliable or valid as professional psychology assumes. The study examines end-placement reports accrued over a 12-year period from 130 supervisors who rated performance in 291 field placements completed by 131 clinical psychology trainees. It is likely that supervisor ratings are affected by a leniency bias. Further, earlier placement ratings are poor predictors of subsequent placement ratings by different supervisors. Ratings on the 11 broad performance dimensions yield a single clinical skills factor within which items congregated into two clusters: Assessment and Intervention; and Interpersonal and Professional skills. Factors that contribute to supervisor bias and strategies to reduce bias and to enhance the value of supervisor ratings are discussed.