The temporal selectivity of additive factor effects on the reaction process revealed in ERP component latencies

An experiment was conducted to relate individual components of the event-related brain potential to specific stages of information processing in a two-choice reaction time (RT) task in a group of undergraduate students. Specifically, the latency of the P300 component and the lateralized readiness potential (LRP) were studied as a function of variations in stimulus degradation and response complexity. It was hypothesized that degrading the stimulus would delay the P300 and LRP to the same extent as RT, and that increasing response complexity would affect RT but not P300 latency. The extant literature did not permit any hypothesis regarding the effect of response complexity on LRP latency. The two task variables were found to have additive effects on RT. As predicted, variations in stimulus degradation influenced the latencies of both components, whereas alterations in response complexity had no effect on P300 latency. A significant new finding was that the onset latency of the LRP remained unchanged across levels of response complexity. The overall pattern of results supports the notion of temporal selectivity of stage manipulations that is derived from discrete stage models of human information processing. Furthermore, these results refine the functional interpretation of the LRP by indicating that within the conceptual framework of a stage model the processes this component indexes succeed the start of response choice but precede the start of motor programming.     

The WISC-III: A reality check

Although the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) is arguably the best instrument currently available for assessing students' intelligence, its use will present practitioners, especially school psychologists, with some unique challenges. Recent research suggests that significant reductions in special education students' WISC-III Verbal, Performance, and Full Scale IQ scores will be found, compared with their previous WISC-R results. This finding will have a profound impact on special education placement decisions. Specifically, students who were previously found eligible for learning disability programs may now no longer evidence the significant discrepancies necessary in order to receive continued services. Conversely, students earlier identified as “slow learners” may now be eligible to receive services for those classified under the category of educably mentally handicapped. In addition, the notion that the WISC-III may underestimate the ability of certain populations of students requires further exploration. This article will address these issues as well as implications for practitioners presently administering the WISC-III.     

Phenomenology and artificial intelligence: Husserl learns Chinese

For over a decade John Searle's ingenious argument against the possibility of artificial intelligence has held a prominent place in contemporary philosophy. This is not just because of its striking central example and the apparent simplicity of its argument. As its appearance in Scientific American testifies, it is also due to its importance to the wider scientific community. If Searle is right, artificial intelligence in the strict sense, the sense that would claim that mind can be instantiated through a formal program of symbol manipulation, is basically wrong. No set of formal conditions can provide us with the characteristic feature of mind which is the intentionally of its mental contents. Formally regarded, such intentionally is an irreducible primitive. It cannot be analyzed into non-intentional (purely syntactic, symbolic) components. This paper will argue that this objection is based on a misunderstanding. Intentionality is not simply something given which is incapable of further analysis. It only appears so when we mistakenly abstract it from time. When we regard its temporal structure, it shows itself as a rule-governed, synthetic process, one capable of being instantiated both by machines and men.     

Verbal reaction time patterns in aphasic adults: consideration for apraxia of speech

Verbal reaction time patterns were compared in aphasic adults presenting anterior and posterior left hemisphere lesions. Reaction Times were measured from simultaneous recording of the subjects' verbal responses and electromyographic activity from three oral-facial sites. Total Reaction Time was fractionated into Premotor Time and Motor Time components to assess latencies associated with motor speech planning and execution. The results suggested that only anterior lesions result in deficits in motor speech planning and/or execution while posterior lesion patients perform no differently than normal. The evidence supports traditional concepts regarding apraxia of speech as being associated with frontal lobe lesions.