Perceptual indices of performance: the measurement of 'inspection time' and 'noise' in the visual system

Memory capacity and intelligence: novel techniques for evaluating rival models of a fundamental information-processing mechanism

Data from a fundamental cognitive task in which participants discriminate the relative frequency of visual or auditory binary stimuli were examined. Accuracy on this task correlates well with psychometric intelligence. The experimental paradigm is highly tractable, lending itself to rigorous analyses of precisely defined simulation models. Numerous models are evaluated, using multiple comparisons between response patterns of individual (and pooled) participants and predictive measures based on simulations for each trial sequence. Implications for theoretical accounts of short-term memory, discrimination, and absolute judgement as well as the measurement of individual differences in cognitive ability, are discussed. The results suggest a reinterpretation of memory capacity and support a new kind of model (with a single estimable parameter) in which discrete, valued units of information are stochastically displaced by further input.

Reductionism and intelligence: the case of inspection time

Successes in science tend to be successful attempts at reduction and causal interaction. The reduction of the interaction of bodies to the laws of motion and the reduction of chemical phenomena to elements and their interactions are good examples. In these cases reductionism leads to observed phenomena being explained by a relatively small number of basic concepts and the laws which govern the interaction of the concepts. The spectrum of inquiry that stretches from common sense to scientific psychology is infused with a tendency toward reductionism. Hippocrates and Galen originated and developed, respectively, the notion that temperamental differences might be reducible to the amounts of four bodily fluids, or humours (black bile, yellow bile, blood and phlegm), that a person produced. Astrologers reduced stable personality differences to the positions of the stars and planets at the time of birth. And differential psychologists have reduced the personality trait adjectives contained in the lexicon to about five major dimensions.

Cerebral asymmetries in inspection time?

Recent studies have suggested that there are low-level processing asymmetries across the cerebral hemispheres, with a right visual field-left hemisphere advantage in tasks involving temporal resolution. In the present report, one such task, inspection time, was measured separately for each cerebral hemisphere in 10 right-handed male subjects over 5 days. A number of methodological improvements were made on previous studies in which a general right visual field-left hemisphere advantage had been found relative to the left visual field-right hemisphere in inspection time performance. The present results suggest that there is no general left hemisphere advantage in inspection time, although there might be asymmetries in practice effects across the hemispheres. The findings also suggest the existence of individual differences in the extent and direction of hemispheric specialisation for this task (ranging from left hemisphere dominance to marked right hemisphere dominance for some subjects) even in right-handed subjects.

The effect of nitrous oxide on the performance of psychomotor tests. A dose-response study

The effect of different nitrous oxide concentrations on the performance of psychomotor tests (inspection time, tapping frequency, critical flicker fusion, picture memory and time sense) was investigated in seven healthy volunteers. The results show a dose-related impairment of memory, a reduction in tapping frequency and an increase in inspection time. A paradoxical increase in critical flicker-fusion threshold was observed. There was no effect on critical fusion-flicker threshold or time sense. Recovery was incomplete for memory tests performed 20 min after withdrawal of nitrous oxide. Subjective effects persisted for several hours.

Effects of nicotine on perceptual speed

Two experiments investigating the effects of nicotine on performance in the inspection time (IT) procedure are reported. Experiment 1 compared ITs in smoking (0.8 mg nicotine cigarette), sham-smoking, and no-smoking conditions. IT was significantly shorter in the smoking condition as compared to both the no-smoking or sham-smoking conditions, suggesting that nicotine enhances early information processing. This result is of particular interest because of the correlation between IT and IQ reported in previous experiments. The nicotine related decrease in IT raises the possibility that nicotine enhances at least a subset of the physiological processes underlying intellectual performance. Experiment 2 examined the persistence of this nicotine related enhancement in IT, and investigated the effects of nicotine across 480 IT trials. Results suggested that ITs derived from the last third of the 480 trials were significantly shorter in the 0.8 mg cigarette condition than in no-smoking condition. The results from these two experiments, taken together with recent work examining the effects of nicotine on the string length measure of AEP waveform complexity and Hick decision time (DT), and studies investigating cognitive functioning and cholinergic system dysfunction in dementia, suggest a role of the cholinergic system in intellectual performance.

A Review of Three Approaches to Cognitive Assessment, and a Proposed Integrated Approach Based on a Unifying Theoretical Framework

In this article, the author reviews three traditions of cognitive assessment: the structural approach (based on factor analytic research), the information-processing approach, and the dynamic approach (based on learning theory). The theoretical background of each assessment approach is sketched and the advantages and disadvantages of each discussed. The author then proposes an integrated two-factor cognitive theory which accommodates all three traditions. Using this theory as a basis, he proposes a design for a test battery which would be appropriate for use in a multicultural context and would identify individuals likely to benefit from developmental opportunities.

Hemispheric asymmetries for an inspection time task: a general left hemisphere temporal advantage?

Two thematic versions of an inspection time task were administered to 18 normal, right-handed subjects. For both tasks, subjects were required to make a categorical discrimination related to the length of two lines. In one version of the task (time task), difficulty was manipulated by varying the exposure duration of the lines. In the other version (length task), difficulty was manipulated by varying the degree to which one line was shorter than the other. The time task was designed to measure the temporal acuity of the observer while the length task was used to gauge subjects' capacity for the same categorical discrimination; independent of temporal acuity. Thus, the two tasks were designed to dissociate the categorical and temporal aspects of the inspection time task. Divided visual field techniques revealed a significant left hemisphere (LH) advantage for the time task, but no asymmetry for the length task. These results could not be accounted for in terms of the categorical nature of the representation. A model, related to the LH's predisposition for the detection of fine temporal events provided a more satisfactory account of the results.

Nonstationarity and the measurement of psychophysical response in a visual inspection-time task

Inspection time (IT) is an index of speed of early visual processing that correlates significantly with measures of higher cognitive ability. An obstacle to the understanding of this important association is the lack of an agreed mechanistic model of the processes involved in IT performance. It is argued here that, whereas in current attempts to model IT processing, stationarity in IT performance is assumed, it is necessary to address this key issue empirically. Two practised subjects undertook 38,400 trials on a standard two-choice visual IT discrimination task. Testing was spread evenly over 60 days. Isotonic regression analysis revealed that both subjects showed nonstationarity in performance over very long periods. The results were not merely due to long-term practice effects; one subject improved in some durations but worsened at others. Therefore, current attempts at modelling in which stationarity in IT performance is assumed must be altered to incorporate the temporal dynamics of IT performance, which might have individual differences.

Age differences in sensitivity, response bias, and reaction time on a visual discrimination task

Twelve young adults (age 21-25 years) and twelve older adults (age 57-65 years) performed a visual discrimination task (parallel lines) in which the following factors were manipulated: the difference in the length of the lines (3% and 9%), signal exposure duration (150, 750, and 2000 ms), and presentation modality (simultaneous and successive). The effect of repeating the task over three blocks was also controlled. Reaction time, sensitivity (d'), the decision criterion (beta), and the level of confidence the subjects had in their responses were measured and analyzed. The reaction time of the older subjects was longer than for younger ones. The difference remained constant across conditions. Signal detection analysis indicated that the ability to discriminate, as measured by d', was the same, on the whole, in the two age groups, but the sensitivity of the older was more affected by signal exposure duration than that of their younger counterparts. Contrary to what might have been expected, the older subjects used a more risky decision criterion than the younger subjects (preferring false alarms to omissions) and did not have significantly less confidence in their responses. Task repetition led to reduced reaction times and to a slightly higher level of confidence, but no age-related effects were found. The findings suggest that, in addition to a perceptual compensatory component, the longer reaction times of the older subjects include a decision-making component not necessary for their level of discrimination accuracy. The outcome of a lower criterion in the older group supports other findings according to which a more conservative decision strategy is not a general, systematic feature of the aged.

Morbidity in nocturnal asthma: sleep quality and daytime cognitive performance

Most patients with asthma waken with nocturnal asthma from time to time. To assess morbidity in patients with nocturnal asthma nocturnal sleep quality, daytime sleepiness, and daytime cognitive performance were measured prospectively in 12 patients with nocturnal asthma (median age 43 years) and 12 age and intellect matched normal subjects. The median (range) percentage overnight fall in peak expiratory flow rate (PEF) was 22 (15 to 50) in the patients with nocturnal asthma and 4 (-4 to 7) in the normal subjects. The patients with asthma had poorer average scores for subjective sleep quality than the normal subjects (median paired difference 1.1 (95% confidence limits 0.1, 2.3)). Objective overnight sleep quality was also worse in the asthmatic patients, who spent more time awake at night (median difference 51 (95% CL 8.1, 74) minutes), had a longer sleep onset latency (12 (10, 30) minutes), and tended to have less stage 4 (deep) sleep (-33 (-58, 4) minutes). Daytime cognitive performance was worse in the patients with nocturnal asthma, who took a longer time to complete the trail making tests (median difference 62 (22, 75) seconds) and achieved a lower score on the paced serial addition tests (-10 (-24, -3)). Mean daytime sleep latency did not differ significantly between the two groups (2 (-3, 7) minutes). It is concluded that hospital outpatients with stable nocturnal asthma have impaired sleep quality and daytime cognitive performance even when having their usual maintenance asthma treatment.

Hemispheric differences in the rates of information processing for simple non-verbal stimuli

An inspection time task, used to gauge differences in speed of information processing between the hemispheres, was administered to 22 normal subjects. It was found that the left visual field-right hemisphere (LVF-RH) exhibited an inferior performance relative to the right visual field-left hemisphere (RVF-LH). These results were consistent with other studies which have found an RVF-LH advantage for the processing of temporal/serial information. The possible ramifications of these results for models of asymmetry which do and do not attribute the left hemisphere's preferential capacity for language to these fundamental processes are then discussed.

Inspection time and high-speed ball games

It has been suggested that successful batsmen in cricket are not distinguished by their fast speed of visual information intake. A study is presented in which a season's batting averages for twenty regular cricketers, all members of the same local team, were correlated with the cricketers' visual inspection times. The correlation was -0.63 (p less than 0.005), suggesting that the successful batsmen were faster at picking up information from briefly presented visual displays. When the age factor was eliminated, the partial correlation between inspection time and batting average remained significant at -0.52 (p less than 0.01). This finding is discussed with respect to the sources of information available from a ball in flight.

The neurophysiological bases of high IQ

It is suggested that the study of human intelligence must ultimately involve the study of brain processes which limit the availability of information. Consideration of EEG/intelligence studies suggests that inconsistent findings may have arisen partly from the expectation of simple rectilinear relationships where relationships are likely to be curvilinear. There are also theoretical and technical problems such that it is difficult to specify what conventional EEG procedures measure. The EEG evoked potential (EP) data described in this paper were obtained with a new and more powerful analytical procedure based on methods and concepts of systems analysis. With this procedure, EP responses are used to ascertain the relative values of parameters which quantify differences in the transmission characteristics of thalamocortical neuron populations. The results obtained from a study of 48 subjects indicate that high IQ is associated with combinations of neurological parameters which determine an intermediate degree of "arousability" in the cerebral cortex and related structures. This relationship is accounted for in terms of the generally optimal effect that an intermediate degree of arousability would have on different neurophysiological processes mediating the acquisition, retention and utilization of information. Thus, with some important qualifications, middling arousability can be conceived as the neurophysiological basis of high general intelligence or "g".

Smoking and human information processing

There is much evidence which indicates that smoking improves various aspects of human information processing (Wesnes 1987). The aim of the present study was to elucidate the stages of human information processing which are improved after cigarette smoking. Twelve regular smokers were tested on three cognitive tasks using a repeated measures design. Tasks used were: rapid visual information processing (RVIP), digit symbol substitution (DSST), and inspection time (IT). Performance parameters derived from these were intended to index different stages of the information processing sequence. Only those measures which involved a motor component were improved after smoking: response time on the RVIP task (P less than 0.025) and DSST performance (P less than 0.1). These findings suggest that central cholinergic pathways are involved in the late, response-related stages of the processing sequence.