Nicholas R. Burns

Inspection Time in the Structure of Cognitive Abilities: Where Does IT Fit?.

Abstract Inspection time (IT) correlates with IQ. This study had four aims: to locate IT within a hierarchical model of cognitive abilities; to test if IT has properties not tapped by other backward masking tasks; to test whether decision time (DT) from ‘odd-man-out’ (OMO) reaction time (RT) measures the same basic process as IT; and to test whether Wechsler performance IQ (PIQ) measures fluid ability (Gf). A battery of psychometric and chronometric tests was administered to 90 adults. Exploratory factor analysis showed that IT loaded on a general speediness factor and a higher-order general ability factor (G) but not on Gf. The results were similar for an alphanumeric pattern backward masking task suggesting that IT does not have special status as a backward masking task. DT and IT measured different processes and PIQ did not measure Gf. Confirmatory factor analyses compared results across alternative models of cognitive abilities but without differentiating one above the others. We conclude that IT does not measure fluid ability, but the question of whether information-processing speed is common to all cognitive abilities is still open.

Dose-related effects of alcohol on cognitive functioning

We assessed the suitability of six applied tests of cognitive functioning to provide a single marker for dose-related alcohol intoxication. Numerous studies have demonstrated that alcohol has a deleterious effect on specific areas of cognitive processing but few have compared the effects of alcohol across a wide range of different cognitive processes. Adult participants (N = 56, 32 males, 24 females aged 18–45 years) were randomized to control or alcohol treatments within a mixed design experiment involving multiple-dosages at approximately one hour intervals (attained mean blood alcohol concentrations (BACs) of 0.00, 0.048, 0.082 and 0.10%), employing a battery of six psychometric tests; the Useful Field of View test (UFOV; processing speed together with directed attention); the Self-Ordered Pointing Task (SOPT; working memory); Inspection Time (IT; speed of processing independent from motor responding); the Traveling Salesperson Problem (TSP; strategic optimization); the Sustained Attention to Response Task (SART; vigilance, response inhibition and psychomotor function); and the Trail-Making Test (TMT; cognitive flexibility and psychomotor function). Results demonstrated that impairment is not uniform across different domains of cognitive processing and that both the size of the alcohol effect and the magnitude of effect change across different dose levels are quantitatively different for different cognitive processes. Only IT met the criteria for a marker for wide-spread application: reliable dose-related decline in a basic process as a function of rising BAC level and easy to use non-invasive task properties.

Reduced corticomotor excitability and motor skills development in children born preterm

•  Children born preterm commonly experience motor and cognitive difficulties, but the physiology underlying this dysfunction is unknown. •  We used transcranial magnetic stimulation techniques and age‐appropriate assessments of motor skills development to investigate neurodevelopment in 151 children born between 25 and 41 weeks of gestation. •  Reduced gestational age at birth was associated with a reduction in corticomotor excitability that persisted in late childhood, poorer development of manual dexterity skills and reduced hemispheric lateralization of hand preference. •  We suggest this reduced corticomotor excitability at least partly reflects reduced white matter integrity and functional connectivity in the brain regions subserving movement control. •  These findings show that preterm birth, which is increasingly common, impacts neuromotor development and related physiology into adolescence. Whether this altered neurophysiology and motor function persists in adulthood is unknown.

Inspection time and general speed of processing

Recent research suggests that the relationship between inspection time (IT) and psychometric intelligence arises because IT is a measure of general speed of processing (Gs). However, hierarchical models of intelligence propose several distinct speed of processing factors; this study examines IT in relation to these multiple speed factors. Participants (N=102) completed tests of speed of processing yielding 18 measures. Factor analysis revealed a second order general speed factor (Gs) and four group factors: perceptual speed, visualisation speed, decision time and movement time. IT correlated with a visualisation speed factor (r=0.36) and with a perceptual speed factor (r=0.28). However, the correlation between IT and perceptual speed was near-zero when the correlation with visualisation speed was partialled out. These findings are consistent with the notion that IT is a measure of Gs but suggest that IT most directly measures speed of visualisation processes. These results are also congruent with research on the psychophysics of IT.

The older people, omega-3, and cognitive health (EPOCH) trial design and methodology: A randomised, double-blind, controlled trial investigating the effect of long-chain omega-3 fatty acids on cognitive ageing and wellbeing in cognitively healthy older adults

BackgroundSome studies have suggested an association between omega-3 long-chain polyunsaturated fatty acids (n-3 LC PUFAs) and better cognitive outcomes in older adults. To date, only two randomised, controlled trials have assessed the effect of n-3 LC PUFA supplementation on cognitive function in older cognitively healthy populations. Of these trials only one found a benefit, in the subgroup carrying the ApoE-ε4 allele. The benefits of n-3 LC PUFA supplementation on cognitive function in older normal populations thus still remain unclear. The main objective of the current study was to provide a comprehensive assessment of the potential of n-3 LC PUFAs to slow cognitive decline in normal elderly people, and included ApoE-ε4 allele carriage as a potential moderating factor. The detailed methodology of the trial is reported herein.MethodsThe study was a parallel, 18-month, randomised, double-blind, placebo-controlled intervention with assessment at baseline and repeated 6-monthly. Participants (N = 391, 53.7% female) aged 65-90 years, English-speaking and with normal cognitive function, were recruited from metropolitan Adelaide, South Australia. Participants in the intervention arm received capsules containing fish-oil at a daily dosage of 1720 mg of docosahexaenoic acid and 600 mg of eicosapentaenoic acid while the placebo arm received the equivalent amount of olive oil in their capsules. The primary outcome is rate of change in cognitive performance, as measured by latent variables for the cognitive constructs (encompassing Reasoning, Working Memory, Short-term Memory, Retrieval Fluency, Inhibition, Simple and Choice-Reaction Time, Perceptual Speed, Odd-man-out Reaction Time, Speed of Memory Scanning, and Psychomotor Speed) and assessed by latent growth curve modeling. Secondary outcomes are change in the Mini-mental State Examination, functional capacity and well-being (including health status, depression, mood, and self-report cognitive functioning), blood pressure, and biomarkers of n-3 LC PUFA status, glucose, lipid metabolism, inflammation, oxidative stress, and DNA damage.Trial registrationAustralia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12607000278437

Inspection time correlates with general speed of processing but not with fluid ability

Inspection time (IT) has been shown to correlate reliably with putative tests of general intelligence such as Ravens matrices and more strongly with performance IQ than with verbal IQ from the Wechsler scales. A common interpretation of this pattern has been that PIQ and matrices tests are measures of fluid ability (Gf) and therefore that IT provides an index of a biological substrate underpinning individual differences in IQ. Marker tests for five of the constructs described in Gf–Gc theory of cognitive abilities were administered to a sample of 64 adults who also completed IT estimation. IT correlated −0.43 (p<0.001) with a test of general processing speed (Gs) but did not significantly correlate with a test of Gf. Results of partial correlation analysis and factor analysis were not consistent with the proposition that general intelligence depends exclusively or substantially on speed of processing. A sub-sample of 37 subjects completed a second marker test for both Gf and Gs. The correlations with IT were consistent with those obtained for the larger sample. The results are interpreted within a hierarchical model of cognitive ability that incorporates speed of processing at the same level as fluid ability and crystallized ability.

Endogenous testosterone levels, mental rotation performance, and constituent abilities in middle-to-older aged men

Evidence from both human and animal studies suggests that gonadal steroids, such as testosterone, exert activational effects on adult spatial behavior. Endogenous testosterone levels decline gradually but variably as men age; it remains to be shown whether these decreases are associated with age-related declines in visuo-spatial performance or constituent abilities indicative of generalized age-related cognitive decline. Ninety-six healthy, community dwelling men aged between 38 and 69 years completed the Vandenberg and Kuse Mental Rotation Test (MRT) together with a battery of tests including processing speed, executive function, perceptual discrimination, working memory, and reaction time measures. Significant main effects of tertiles of calculated free testosterone levels (cEFT) were found on composite measures of processing speed, executive function, and perceptual discrimination ability in a subset of men aged over 50 years in age and crystallized intelligence controlled analyses; higher cEFT levels were associated with poorer performance. Hierarchical multiple regression and path analyses on the whole data set showed that cEFT levels negatively moderated processing speed performance, which in turn predicted both working memory and MRT performance with aging. Together these data suggest that age-related declines in endogenous testosterone levels in healthy middle-to-older aged men are not associated with generalized age-related cognitive decline.

Testing the interpretation of inspection time as a measure of speed of sensory processing

Abstract Explaining the relationship between inspection time (IT) and IQ depends on understanding the psychophysics of IT. Whites (1996, Personality and Individual Differences , 20, 351–363) argument that IT is a measure of temporal resolution within the visual system was tested. Two predictions were made on the basis of Whites argument that IT does not depend on line-length discriminations but on discriminating target from mask. First, radically different target-mask configurations would result in the same response outcome. Second, increasing the number of alternative targets would not increase IT. Three subjects performed four pattern masking tasks presented on a LED display with stimulus onset asynchronies (SOAs) ranging from 0–75 msec and using three configurations of backward mask. Results met the predictions. Psychometric functions for different tasks were near identical and IT estimates did not increase as the number of targets was increased. It is therefore possible that the IT-IQ relationship applies generally to pattern backward masking tasks. Results also confirmed the prediction (Levy, 1992, Personality and Individual Differences , 13, 987–1002; White, 1996, Personality and Individual Differences , 20, 351–363) that discriminative accuracy does not rise above chance level until after some small, non-zero SOA.

Are individual differences in performance on perceptual and cognitive optimization problems determined by general intelligence

Studies of human problem solving have traditionally used deterministic tasks that require the execution of a systematic series of steps to reach a rational and optimal solution. Most real-world problems, however, are characterized by uncertainty, the need to consider an enormous number of variables and possible courses of action at each stage in solving the problem, and the need to optimize the solution subject to multiple interacting constraints. There are reliable individual differences in people’s abilities to solve such realistic problems. It also seems likely that people’s ability to solve these difficult problems reflects, or depends on, their intelligence. We report on a study of N = 101 adults who completed a series of visual optimization problems (Traveling Salesperson, Minimum Spanning Tree, and Generalized Steiner Tree Problems), as well as a cognitive optimization problem (a version of the Secretary Problem). We also characterized these individuals along three relevant and important cognitive abilities dimensions—fluid ability, visuo-spatial ability, and cognitive processing speed. Modeling of covariance structures indicated that performance on both types of optimization problems relies on general intelligence and raises the possibility that they can be used to assess intelligence.

Screening for depression and anxiety in spinal cord injury with DASS-21

Study design:Comparison of two self-report instruments with a structured diagnostic interview.Objective:To investigate the properties of the Depression Anxiety Stress Scales-21 (DASS-21) in patients with spinal cord injuries.Setting:South Australian Spinal Cord Injuries Service, Hampstead Rehabilitation Centre, Northfield, South Australia.Methods:Forty paraplegic or tetraplegic patients participated. Two self-report measures, DASS-21 and Brief Symptom Inventory (BSI), assessed Depression, Anxiety and Stress. These measures were compared with each other and with diagnoses based on the Mini International Neuropsychiatric Interview.Results:Mean scores on both self-report measures were below clinical threshold levels. Prevalence rates of anxiety and depression were higher on DASS-21 than on BSI. DASS-21 was as sensitive as BSI, but had lower specificity to detect anxiety and depression.Conclusion:DASS-21 is a promising screening measure for patients with spinal cord injury in a rehabilitation setting. It has greater sensitivity for identifying those with possible anxiety disorders than it does for those with depressive disorders.