Intelligence, reaction times, and peripheral nerve conduction velocity

Two studies (with sample sizes of 85 and 88) are reported that investigated relationships among measures of intelligence, speed of information processing, and peripheral nerve conduction velocity (NCV). In both studies, NCV was significantly correlated with IQ scores (rs = .42 and .48) and with reaction times (RTs; rs = −.28 and −.18): Thus, faster NCV was associated with higher IQ scores and faster speed of processing. In both studies, NCV and RTs contributed significantly, in combination, to the prediction of fullscale IQ (shrunken multiple Rs = .53 and .57), but the expected pattern of causal relationships between the variables was not borne out. The results are interpreted in terms of a “neural efficiency” model of intelligence, which has recieved support from other studies of physiological correlates of human intelligence.     

Anonymous Skeptics: Swinburne, Hick, and Alston

Book reviewed:
Lance Ashdown. Anonymous Skeptics: Swinburne, Hick, and Alston. Reviewed by John H. Whittaker     

Learning and locomotor reaction times

To help measure contributions by learning to latencies of complex locomotor responses, an operant stimulus-response unit was constructed and timed during human treadmill walking. A light flash served as discriminative stimulus (Sd) to produce electromyographic activity (EMG) of predefined filtered amplitude and duration by the leg muscle, rectus femoris (RF). A computer scored every EMG as successful or not (indicated by a high or low tone, respectively). The EMG burst also had to occur within successively shorter performance durations (PDUR), to a criterion of 80% successful responses. Among six adults, the shortest estimated reaction time was 110 msec. Relative strength of the operant unit was measured in relation to RF activity that occured in non-light step cycles or that was a by-product of the reinforcement regimen. It was proposed that operant latencies, after being minimized by specific conditioning regimens, can permit accurate timing of intervening neural events.     

John Hick, Philosophy of Religion, and the Clarity of God's Existence

Book reviewed in this article:
David Cheetham, John Hick: A Critical Introduction and Reflection     

Subjective expectancy and choice reaction times

Previous findings suggested that selective response times might be affected both by the inter-stimulus interval and by the probability of occurrence of the stimulus for reaction. These two factors have been tested independently and have been found to influence reaction times in a fashion that an expectancy hypothesis would predict.     

Visual and auditory choice reaction times

Choice reaction times are measured for three values of a priori signal probability with three well-practiced observers. Two sets of data are taken with the only difference being the modality of the reaction signal. In one set of conditions it is auditory, in the other, visual. The auditory reaction times are faster than the visual and in addition several other differences are noted. The latency of the errors and correct responses are nearly equal for the auditory data. Error latencies are nearly 30% faster for the visual data. Non-stationary effects, autocorrelation between successive latencies and non-homogeneous distribution of errors, are clearly evident in the visual data, but are small or non-existent in the auditory data. The data are compared with several models of the choice reaction time process but none of the models is completely adequate.     

Choice reaction times in children: Error and post-error responses,and the repetition effect

Analysis of the frequency and nature of error and post-error responses in the serial choice reaction times (RTs) of children between 5 and 12 years essentially replicate findings in adults. Errors are few and fast, tend to be made on fingers closely related to the correct responding finger, and are followed by a marked slowing in response rate. This pattern of results is interpreted in terms of a strategy to optimize performance with respect to instructions emphasizing both speed and accuracy. Importantly, this may be seen to reflect the activity, even in the youngest of children, of a finely-tuned feedback mechanism for error detection. Only the extent of immediate post-error slowing shows a decline with age, and is referred to improvements in response programming. Repetition RT is much faster than alternation RT (the “Repetition Effect”) and improves much less rapidly with age. Reduction of the Repetition Effect with age is consistent with theories of RT in which signals are categorized by retrospective search in short-term memory. The girls' advantage in gross RT is found to be confined to alternation RT only. The particular contribution of alternation RT both to the development of, and sex difference in, gross RT is related to the greater response organization involved in rapidly switching between fingers and hands.     

Choice reaction times and the theory of intermittency in human performance

One visual signal, drawn from two equi-probable alternatives, was followed at a variable interval by a similar signal, also drawn from two equi-probable alternatives. The relationship between reaction time to the second signal and the interval between signals was studied under the following conditions: (1) Subjects were trained from the beginning to regard the first signal as irrelevant. (2) Subjects were asked to report on the nature of the first signal after they had responded to the second. The interval between signals was one of the five values, 50, 100, 150, 200, 250 millisec. In the regular interval situation the same interval was used over a block of 20 trials. In the random interval situation the values of the interval were randomly arranged, with equal frequency within each block of 20 trials.

The results showed: (1) In the random interval situation there was a definite disturbing effect of the first signal on the reaction time to the second, despite the fact that subjects were trained to disregard the first signal. However, the delays in reaction time were significant only at the shortest interval, 50 millisec. (2) In the regular interval situation this disturbing effect was not evident. (3) The additional requirement of having to report on the nature of the first signal produced no consistent increase in reaction time to the second signal. Some implications of these results for the conception of the human operator as a channel of limited capacity are discussed.     

Phonatory initiation,termination, and vocal frequency change reaction times of stutterers

Four types of voice reaction times were investigated for eight adult stutterers and eight control subjects using a vocal shadowing paradigm. These were voice initiation and termination reaction times (VIT and VTT, respectively) and voice frequency-shift intiation and termination reaction times (SIT and STT, respectively). Results indicated that the stutterers were slower in VIT, but were as fast as their control subjects in VTT, SIT, and STT. It was suggested that a laryngeal discoordination problem of stutterers lies primarily in the stage of adduction (turning on the voicing) rather than in the stage of abduction (turning off the voicing) or in finer frequency control at the larynx.     

Manual reaction times and error rates in stutterers.

In this study 18 stutterers and 18 nonstutterers were presented trials on which they should press a button as fast as possible, intermixed with trials which required no responding. Stutterers had slightly faster reaction times but also made slightly more errors, that is, they tended to press the button when they should not have done so. As neither difference was significant, it was concluded that stutterers did not differ from normal speakers in manual reaction speed, nor did they choose a different speed-accuracy trade-off criterion for the given task.     

Simple reaction times to the onset,onset, and contrast reversal of sinusoidal grating stimuli

Response latencies to the onset, offset, and contrast reversal of sinusoidal gratings over a range of spatial frequencies were measured. For gratings of constant physical contrast, RT was monotonically related to spatial frequency regardless of presentation mode. Comparison of RTs to 1.0- and 9.0-cycle/deg gratings adjusted to equal apparent contrast showed that the RT shifts cannot be directly attributed to contrast sensitivity differences. It is concluded that spatial-frequency-dependent processing delays occur regardless of which temporal property of the stimulus the subject must respond to.     

Suitability of the IBM XT,AT, and PS/2 keyboard,mouse, and game port as response devices in reaction time paradigms

The IBM PC keyboard is a convenient response panel for subjects in a reaction time task when the stimuli are presented on the same machine. However, there is a mean delay of about 10 msec and a random error of ±7.5 msec (±5 msec on the AT or PS/2). Our analyses show that for typical single response experimental situations, this added variance is acceptable. With mouse buttons, timing resulted in a delay of 31 ±2 msec if the mouse ball was steady but 45 ±15 msec if it was moving, and a 25-msec refractory period before a second response could be detected. With keys connected to the game port, timing was accurate to 1 msec. For timing the interval between two nearly simultaneous responses, only the game port method is recommended. Any research application should provide an external check on reaction timing accuracy and should correct any mean error.     

Methodological issues in measures of imitative reaction times

Ideomotor (IM) theory suggests that observing someone else perform an action activates an internal motor representation of that behaviour within the observer. Evidence supporting the case for an ideomotor theory of imitation has come from studies that show imitative responses to be faster than the same behavioural measures performed in response to spatial cues. In an attempt to replicate these findings, we manipulated the salience of the visual cue and found that we could reverse the advantage of the imitative cue over the spatial cue. We suggest that participants utilised a simple visuomotor mechanism to perform all aspects of this task, with performance being driven by the relative visual salience of the stimuli. Imitation is a more complex motor skill that would constitute an inefficient strategy for rapid performance.     

Hemispheric equality in reaction times to emotional and non-emotional nouns

Twenty presentations of 6 emotional and 6 non-emotional words in mixed random orders were monaurally presented to the right or left ear. Using the left hand, subjects pushed one of two response buttons indicating type of word heard. Performance improved in later trials and emotional words were recognized more quickly regardless of ear presentation. No differences were associated with the separate ear presentations. Equivalent hemispheric performance indicates equal processing sensitivity to four-letter emotional and non-emotional nouns and substantiates the right hemisphere's verbal processing capability for simple nouns.