Inspection Time Performance Research Articles

Age-related decrease in motor contribution to multisensory reaction times in primary school children.

Traditional measurement of multisensory facilitation in tasks such as speeded motor reaction tasks (MRT) consistently show age-related improvement during early childhood. However, the extent to which motor function increases with age and hence contribute to multisensory motor reaction times in young children has seldom been examined. Thus, we aimed to investigate the contribution of motor development to measures of multisensory (auditory, visual, and audiovisual) and visuomotor processing tasks in three young school age groups of children (n = 69) aged (5−6, n = 21; 7−8, n = 25.; 9−10 n = 18 years). We also aimed to determine whether age-related sensory threshold times for purely visual inspection time (IT) tasks improved significantly with age. Bayesian results showed decisive evidence for age-group differences in multisensory MRT and visuo-motor processing tasks, though the evidence showed that threshold time for visual identification IT performance was only slower in the youngest age group children (5−6) compared to older groups. Bayesian correlations between performance on the multisensory MRT and visuo-motor processing tasks indicated moderate to decisive evidence in favor of the alternative hypothesis (BF10 = 4.71 to 91.346), though not with the threshold IT (BF10 < 1.35). This suggests that visual sensory system development in children older than 6 years makes a less significant contribution to the measure of multisensory facilitation, compared to motor development. In addition to this main finding, multisensory facilitation of MRT within race-model predictions was only found in the oldest group of children (9−10), supporting previous suggestions that multisensory integration is likely to continue into late childhood/early adolescence at least.

158 The Association Between Sleep Spindles and Cognitive Function in Middle-Aged and Older Men: A Population-Based Cohort Study

Abstract Introduction Sleep spindles are thought to play an important role in learning and memory. The association between sleep spindles and cognitive function and the potential confounding influence of obstructive sleep apnea (OSA) is uncertain. We examined the cross-sectional association between sleep spindles and cognitive function controlled for OSA in a sample of community dwelling middle-aged and older men. Methods Participants of the Florey Adelaide Male Ageing Study (n=477) underwent home-based polysomnography. These participants also completed the inspection time (IT) task, trail-making test part A (TMT-A) and part B (TMT-B), and Fuld object memory evaluation (FOME) test. Spindle metrics derived from sleep electroencephalography (n=356) included occurrence (total number) and fast (13-16 Hz) and slow (11-13 Hz) spindle density (number/minute) during N2 and N3 sleep. Linear regression models were adjusted for age, OSA, education, obesity, cardiovascular disease, diabetes, smoking, and alcohol risk. Results In covariate unadjusted analyses, higher spindle occurrence during N2 sleep was associated with better IT, TMT-A, TMT-B, and FOME performance (all p&amp;lt;0.05). Spindle density (fast and slow) during N2 and N3 sleep (slow spindles only) was associated with better inspection time, TMT-A, and TMT-B performance (all p&amp;lt;0.05). Fast spindle density during N2 sleep was also associated with better FOME performance (B=1.03, 95% CI [0.47, 1.59], p&amp;lt;0.05). In covariate adjusted analyses, higher spindle occurrence during N2 sleep was independently associated with better IT (B=-0.002, 95% CI [-0.004, 0.000], p=0.046), while fast spindle density during N3 sleep was independently associated with worse TMT-B performance (B=0.12, 95% CI [0.03, 0.21], p=0.011). Conclusion Specific sleep spindle metrics during N2 and N3 sleep were independently associated with better visual processing speed and worse executive attention, suggesting a differential association between cognitive function and spindles during N2 and N3 sleep. The utility of sleep spindles for predicting cognitive impairment needs investigation in prospective studies. Support (if any) National Health and Medical Research Foundation, Adelaide Institute for Sleep Health, Hospital Research Foundation, and ResMed Foundation.

Visual processing is diminished during movement execution.

Recent research has suggested that visual discrimination and detection may be enhanced during movement preparation and execution, respectively. The current study examined if visual perceptual processing is augmented prior to or during a movement through the use of an Inspection Time (IT) task. The IT task involved briefly presenting (e.g., 15–105 ms) a “pi” figure with differing leg lengths, which was then immediately masked for 400 ms to prevent retinal afterimages. Participants were subsequently required to choose which of the two legs was longer. In Experiment 1, participants (n = 28) completed the IT task under three movement conditions: no-movement (NM), foreperiod (FP), and peak velocity (PV). In the NM condition, participants solely engaged in the IT paradigm. In the FP condition, the IT stimulus was presented prior to movement execution when response planning was expected to occur. Finally, in the PV condition, participants made a rapid movement to a target, and the IT stimulus was presented when their limb reached peak velocity. In Experiment 2, participants (n = 18) also performed the IT task in the PV and NM condition; however, vision of the limb’s motion was made available during the PV trials (PV-FV) to investigate the potential influence of visual feedback on IT performance. Results showed no significant differences in performance in the IT task between the NM and FP conditions, suggesting no enhancement of visual processing occurred due to response preparation (Experiment 1). However, IT performance was significantly poorer in the PV condition in comparison to both the NM and FP conditions (Experiment 1), and was even worse when visual feedback was provided (Experiment 2). Together, these findings suggest that visual perceptual processing is degraded during execution of a fast, goal-directed movement.

Reversing the speed–IQ correlation: Intra-individual variability and attentional control in the inspection time paradigm

Elementary cognitive tasks (ECTs) are simple tasks involving basic cognitive processes for which speed of performance typically correlates with IQ. Inspection time (IT) has the strongest IQ correlations and is considered critical evidence for neural speed underlying individual differences in intelligence. However, results from Bors et al. [Bors, D.A., Stokes, T.L., Forrin, B. & Hodder, S.L., (1999). Inspection Time and Intelligence: Practice, strategies, and attention. Intelligence, 27, 111–129.] suggest task consistency may underlie this shared variance. One possibility is that performance consistency reflects attentional mechanisms, as previous research has shown relationships between attentional control and cognitive performance. In study 1, participants were administered the Raven's Advanced Progressive Matrices and performed an alternative version of the IT task to measure individual trial-by-trial consistency expressed as the standard deviation of IT (ITSD). The alternative procedure yielded IT–IQ correlations similar to those obtained in previous studies and ITSD accounted for the IT–IQ variance. A second experiment tested whether ITSD measures attentional control, as participants simultaneously performed the IT task and an attention-demanding verbalization task. Under these conditions, high IQ participants performed worse on IT. These results suggest IT performance may reflect individual differences in attentional control and that this variable may account for the variance shared between IT and IQ.

Inspection time in non-demented older adults with mild cognitive impairment

The aim of this study was to examine inspection time (IT) performance in older adults with mild cognitive impairment (MCI), who are at higher risk of developing further cognitive decline or dementia. IT is described as an index of speed of informational intake. IT correlates with measures of fluid intelligence and is possibly a marker for the integrity of the cholinergic system of the brain. IT may therefore be useful in aiding the diagnosis of early-stage progressive cognitive impairment. The current study compares IT in 28 people with MCI to 28 age, gender and education-matched controls. The computer-based, visual IT task required participants to discriminate between two visual stimuli that were presented for brief periods. Participants’ IT performance was compared to their performance on cognitive and memory tasks. Group comparison showed that participants with MCI performed significantly worse on IT than controls and was not affected by years of education. In combination with other clinical, neuropsychological and biological tests, IT may be a useful assessment tool for improving the identification of older adults at risk for clinically relevant cognitive decline.

Speed of processing and individual differences in IQ in schizophrenia: General or specific cognitive deficits?

Introduction. The aim of this study was to re‐examine the role of cognitive processing speed in the vulnerability to schizophrenia, using an inspection time (IT) task that does not require a speeded manual response. Since IT consistently correlates with intelligence, the relationship between IT and general intelligence was also explored. Correspondence should be addressed to Dr J. C. Badcock, Centre for Clinical Research in Neuropsychiatry, Private Mail Bag No 1, Claremont, Western Australia 6010; e‐mail: jobad@cyllene.uwa.edu.au. The research was supported by grants from the National Health and Medical Research Council and infrastructure funding from the Department of Health of Western Australia (CPP Grant 9937102 NHMRC, HP Grant 960579 NHMRC). We would, first and foremost, like to thank the patients, community volunteers, and their families who participated in this research. The assistance of nursing and medical staff at Graylands Hospital and related clinics, and their continuing support of our research, are gratefully acknowledged. Methods. Patients with schizophrenia were compared with unaffected siblings of schizophrenia patients and healthy controls on a visual IT task. Both speed and variability of IT performance were examined. Current intellectual ability (IQ) was estimated with the Shipley Institute of Living Scale (SILS), which yields separate assessments of verbal and abstraction abilities. Results. Schizophrenia patients produced ITs that were significantly slower and more variable than either unaffected siblings or healthy controls. These results are not related to demographic or clinical variables. A significant negative correlation was obtained between IT and IQ; specifically, longer IT values were associated with abstraction scores only. Conclusions. These findings confirm that basic cognitive processing efficiency is impaired in patients with schizophrenia. In contrast, ITs in unaffected siblings did not differ from healthy controls, in line with their better IQ test scores. Implica tions for models of general and specific heritable dimensions in schizophrenia are discussed.

An investigation of the relationship between trait emotional intelligence and emotional task performance

This study examined the relationships between trait emotional intelligence (EI) and tasks involving the recognition of facial expressions of emotion. Two facial expression recognition tasks using the inspection time (IT) paradigm assessed speed of emotional information processing. An unspeeded emotion recognition task was also included, and a symbol IT task was used to assess speed of processing of non-emotional information. It was found that scores on all three emotion-related tasks were strongly intercorrelated, as were scores on the three IT tasks. The two emotional IT scores remained significantly correlated when symbol IT performance was partialled out. This finding, together with the associations between the speeded (IT) and unspeeded face tasks suggests that the association between the emotional IT tasks is not entirely accounted for by general processing speed, and that a general emotion-processing ability also contributes to performance on these tasks. An EI subscale assessing Appraisal of Emotions was significantly correlated with performance on the emotional IT tasks, suggesting that self-reports of emotional perception ability do relate to performance measures.

Examining neurochemical determinants of inspection time: Development of a biological model

Inspection time (IT), an information-processing correlate of psychometric intelligence, has been extensively studied. Previous research has shown that IT is a reliable correlate of psychometric intelligence across different developmental periods, mirroring developmental trends of fluid intelligence. Despite this extensive previous literature, very little is known about the biological basis of IT. In the present review, we discuss recent results from our laboratories examining the neurochemical determinants of IT. In this review, we outline the significance of several studies in which performance on the IT task is measured before and after modulating key human central nervous system (CNS) neurotransmitters and receptor systems (e.g., cholinergic, serotonergic, noradrenergic, and dopaminergic systems). The results of these studies indicate a primarily cholinergic basis for IT, although other aspects of psychometric intelligence may have serotonergic and dopaminergic determinants in addition to a cholinergic basis. The results are consistent with data reporting cholinergic depletion and impaired IT performance in dementia of the Alzheimer's type (DAT). Speculatively, we propose that compounds that enhance the release of the neurotransmitter acetylcholine (Ach) will improve IT and the variance that IT shares with IQ test performance.

Strategy use and feedback in inspection time

There is a consensus that psychometric intelligence correlates significantly with inspection time (IT), a putative measure of the efficiency of the early stages of visual information processing. Controversy exists as to whether IT is a cause or a consequence of IQ differences. It has been suggested that individuals with a high IQ form macrolevel strategies which undermine the microlevel processing assumptions of IT testing, and that feedback given in the early stages of IT testing facilitates strategy formation. One such strategy involves detecting apparent movement in IT stimulus-mask displays. We manipulated feedback during IT testing and found: (1) no evidence that feedback encouraged the formation of strategies; and (2) that feedback did not aid performance on IT. Strategy users did not have superior IT performance. The overall level of strategy reporting was low, presumably because an effective backward mask was employed. These results do not support a causal role for strategies in the correlation between IT and psychometric intelligence; however, they are congruent with the notion that strategy reporting in the IT task is a verbal epiphenomenon. With appropriate stimulus presentation devices and an effective backward mask many of the stimulus-mask artefact problems that lead to strategies in the IT task may be avoided.

Visual information processing and intelligence

Measures of inspection time (IT) have robust, moderately-sized correlations with IQ-type test scores. However, the reason for the IT-IQ correlation is not understood. Although the original theory asserted that IT performance was based on a single parameter—essentially speed of visual processing—peculiarities of the task have afforded other interpretations of IT differences and the IT-IQ association. In the present report two new visual processing tasks, visual change detection (VCD) and visual movement detection (VMD) are found to be correlated at or above .4 with IT and with non-verbal scores from the Alice Heim 4 test of general intelligence. VCD and VMD, in common with IT, assess the stimulus duration that is required by subjects in order to make an accurate discrimination. VCD and VMD, however, require a broader attentional focus than IT and do not involve backward masking. Measures of contrast sensitivity, a difficult discrimination task in which stimuli are not time-limited, had near-to-zero correlations with other visual processing tasks and with IQ-type test scores. We tested the hypothesis that only the latent trait derived from the speeded visual processing tasks (rather than task-specific features) would correlate with cognitive ability, and this was supported. The present study adds weight to the view that it is the ability to make accurate discriminations in the face of limited stimulus time that causes IT to correlate with psychometric intelligence. The psychological correlates of VCD, in terms of neural circuits that detect “difference” suggest a new line of investigation into the psychobiological bases of human intelligence.

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.

Smoking, string length and intelligence

Over the last decade a number of studies have reported significant relationships between physiological and semi-physiological measures of performance—the string length measure of AEP waveform complexity, inspection time (IT) and reaction time (RT) and psychometric intelligence. At present, the neurophysiological mechanism(s) mediating this relationship are unknown. However, some recent smoking studies have reported that RT and IT performance is significantly enhanced in smoking (nicotine) conditions compared to sham smoking (no nicotine) or no-smoking conditions, which suggests performance on such tasks may be mediated by cholinergic systems. In order to further investigate this relationship, the string length which arguably provides the highest correlation with IQ was measured under smoking and non-smoking conditions. As predicted, string lengths were significantly increased in the smoking condition, suggesting that nicotine may enhance the neurophysiological processes underlying general cognitive ability.

The inspection time not studied: Processing speed ability unrelated to psychometric intelligence

In two experiments ( n = 178 and n = 190), spatial, quantitative, and verbal inspection-time (IT) and visual-search (VS) tasks were administered to the same subjects along with measures of general intelligence (IQ). IT tasks were length, numeracy, and letter-string classifications made difficult by backward masking. IT tasks used accuracy as a performance measure. VS tasks were searches of figural, numeric, or word targets in arrays of similar items. VS tasks used reaction time under a high accuracy set as a performance measure. In both experiments IT correlated significantly to both IQ and VS, and in both experiments the negative correlation of IT to VS was significant controlling for IQ. The results provide evidence that IT performance has a component related to IQ tests and an independent component related to other processing speed tests such as visual search.

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.

Inspection time in two childhood age cohorts: A constant or a developmental function?

The development trend of inspection time (IT) was investigated by comparing performances of eleven 5–6‐year‐olds and thirteen 11–12‐year‐olds, matched for IQ using Raven's Coloured Progressive Matrices (CPM). Initial age‐related differences in IT were substantially reduced by extended practice but remained statistically significant after practice across 20 and more successive estimates had reduced IT performance to asymptotic levels. Relative rate of improvement in IT performance was not related to CPM and consideration of attentional variability and possible fatigue effects suggested that these variables could not account for the final difference between the samples in mean IT. Early 1T‐CPM correlations within cohorts were above − .5 but after eight estimates diminished steadily, eventually to negligible proportions in both age samples. This outcome was interpreted as the consequence of a shift in the type of information being processed, since a majority of children in both age samples reported learning to use post‐stimulus cues of apparent movement. Overall, results supported the hypothesis that speed of central processing increases as a function of mental age; but also highlighted methodological shortcomings in IT as an index of mental speed free from the influence of cognitive strategies.

Blood lead levels, reaction time, inspection time and ability in Edinburgh children

The influence of blood lead levels on measures of inspection time (IT) and reaction time (RT) was studied in a sample of 501 6‐ to 9‐year‐old children. Both IT and RT performance were worse at higher blood lead levels, but the relationship was stronger for IT. The relationship between blood lead and RT was no longer significant after control for social and family background, whereas that between blood lead and IT remained significant. It is suggested that the IT task described here measures the ability to sustain attention, rather than perceptual speed per se.All the IT and RT measures correlated with ability and attainment, assessed by the British Ability Scales. The correlations with the combined ability score were modest, .31 for the IT error rate at long presentation times and .30 for median reaction time. The median reaction time and the IT error rates contributed independently to the prediction of the ability score. The influence of lead on the IT error rates no longer achieved statistical significance after control for ability, whereas the influence of lead on ability remained significant after control for IT error rates.

Visual and auditory inspection time: Their interrelationship and correlations with IQ in high ability subjects

Results from three visual inspection time (IT) tests and a new auditory IT test were correlated with psychometric measures of intelligence in an undergraduate population. The four IT tests correlated with each other at similar levels to the psychometric test intercorrelations. The range of raw IQ-IT correlations agreed with the predicted -0.35 that has been reported previously. Corrected correlations indicated that the true IQ-IT correlation is in the region of -0.55. This study corroborates the hypothesis that a substantial proportion of the IQ variance is located in individual differences in perceptual intake speed, both visual and auditory. The intercorrelation of the auditory and visual IT Tests indicates that IT is, in part, due to differences in nervous system functioning in general. The results do not support a specific strategy theory of IT performance.

The effect of attention on developmental differences in inspection time

Inspection time (IT), an estimate of the speed of perceptual encoding, has been shown to relate to IQ in adults and to differences in mental age in children. This paper investigates the possibility that older children have faster ITs because of improvements in attentional factors related to task performance rather than because of any age differences in processing speed. Attentional factors were manipulated in two ways. First the IT task was either self, or externally, paced. The hypothesis was that allowing the children to pace themselves should reduce the influence of distractibility on performance and reduce any age difference in IT. Second, the IT stimulus was presented after either a fixed, or a random, foreperiod. The hypothesis was that any advantage the older children have in involuntary attentional processes would be removed when the foreperiod was random, again reducing the age difference in IT. Seventy-two Ss. 40 12-yr-olds and 32 8-yr-olds, were given the task in one of four conditions, self or externally paced, with a fixed or random, foreperiod, and measures of IT were taken. There was an effect of age on one of the IT measures but it did not interact with any of the attentional variables. The random foreperiod produced significantly longer ITs in the externally paced condition. The normally robust relationship between MA, IQ and IT was either weak or absent in the data. The conclusion is that are attentional influences on IT performance but they detract from, rather than induce, the relationship between IT, age and intelligence.

Intelligence and inspection time in normal and mentally retarded subjects.

The present experiments explore the generality of some recent findings relating IQ to a measure known as Inspection Time (IT)--the exposure duration necessary to judge which of two briefly presented straight lines is the longer. In the first study IT and verbal and performance IQ scores were obtained from a large group of normal six- and seven-year-old children. In contrast to some previous suggestions verbal IQ and full-scale IQ did not correlate significantly with IT, and performance IQ showed only a weak correlation with IT (r = -0.29). In the second experiment IT was found to correlate much more highly with performance IQ in a sample of mentally retarded subjects (r = -0.71). Some possible implications of these results for theories of intelligence and of mental retardation are discussed.