Brian Mackenzie

IQ, Inspection time, and response strategies in a university population

Abstract The relationship between Inspection Time (a perceptual discrimination task designed to estimate the rate at which a subject processes sensory input) and the Wechsler Adult Intelligence Scale (WAIS) was assessed in a sample of 29 university students. Sixteen of the subjects (“strategy users”) independently developed a strategy for performing the task, based on apparent movement cues. The remaining 13 (“non-users”) did not develop the strategy and could not easily be trained in its use. Strategy users had slightly faster Inspection Times than non-users, but were not significantly different from the non-users on the WAIS or any of the subtests. However, the two groups differed substantially in the relationship of Inspection Time to IQ. In the strategy users, Inspection Time was not significantly related to IQ or to any of the WAIS subtests. In the non-users, Inspection Time was highly correlated with Performance IQ and with scores on two of the subtests. Methodological implications of the difference...

How fragile is the relationship between inspection time and intelligence: The effects of apparent-motion cues and previous experience

Abstract Previous research is cited which indicates that there is a strong relationship between inspection time (IT) and conventional measures of intelligence, but only for those S s who are not able to make use of apparent-motion cues in performing the experimental task. For those S s (the majority) who are able to make use of such cues, there is no significant relationship. The present study confirmed this difference between ‘cue users’ and ‘non-users’ in a sample of 37 male volunteer S s of normal intelligence. For the 15 cue non-users, there was a high correlation between IT and scores on the Advanced Progressive Matrices test; for the cue users, the correlation did not approach significance. Cue users, when interviewed, indicated that they attended to apparent-motion cues consistently, over a wide range of stimulus exposure durations, and never made use of alternative cues to perform the experimental task. Non-users indicated either that they alternated between different approaches to the task or that they could not identify any cues to attend to. In a separate experimental task, cue users did not differ from non-users in the minimum stimulus onset asynchrony needed to perceive apparent motion. An almost equal proportion of cue users and non-users played video games regularly; playing video games had no independent effect on IT.

The relationship between speed of information processing and cognitive ability

Speed of information processing as measured by various reaction time and inspection tasks has been shown to correlate with psychometric intelligence, and it has been suggested that general intelligence (g) is determined to some degree by the speed that information is processed. If this is so, then various measures of speed of information processing should correlate substantially with each other, and each should also correlate with a wide range of psychometric tests that load on g. Alternatively, intelligence may be considered to be a multi-faceted complex of partially related abilities with specific abilities being dependent upon specific cognitive processes. If this is the case, it should be possible to discover independent cognitive processes, some of which correlate with one facet or broad ability and some with another. This paper presents three experiments in which the relationship between intellectual ability and four speed of information processing measures was examined. These were rate of memory scanning, rate of retrieval of information from long term memory, speed of stimulus-response mapping and inspection time (IT). Results showed that correlations between IT and most reaction time measures of speed of information processing were low, and that correlations between different versions of IT were negligible. In addition, some cognitive tasks with verbal material (memory scanning rate for digits and Posner letter matching IT) correlated most substantially with Verbal Reasoning whereas non-verbal (two-line) IT consistently correlated with tests loading on g. It was thus suggested that while non-verbal IT may be a measure of a perceptual speed attribute that contributes to mental functioning, other “speed of information processing” parameters may be more specific to a subset of abilities.

Modality-Specific Differences in the Processing of Spatially, Temporally, and Spatiotemporally Distributed Information

The extent to which auditory, tactile, and visual perceptual representations are similar, particularly when dealing with speech and speech-like stimuli, was investigated. It was found that comparisons between auditory and tactile patterns were easier to perform than were similar comparisons between auditory and visual stimuli. This was true across a variety of styles of tactile and visual display, and was not due to limitations in the discriminability of the visual displays. The findings suggest that auditory and tactile representations of stimuli are more alike than are auditory and visual ones. It was also found that touch and vision differ in terms of the style of information distribution which they process most efficiently. Touch dealt with patterns best when the pattern was characterised by changes across time, whereas vision did best when spatially or spatiotemporally distributed patterns were presented. As the sense of hearing also seems to specialise in the processing of temporally ordered patterns, these results suggest one way in which the senses of hearing and touch differ from vision.

Irlen lenses in the treatment of specific reading disability: An evaluation of outcomes and processes

Abstract This study aimed at determining the relationship between Men lenses and reading ability. Using a variety of visual, phonological, workhg memory, and reading tasks, the efficacy of Irlen lenses with a reading-disabled population was investigated. Sixty subjects (20 normal readers, 20 specifically disabled readers with Irlen lenses and 20 specifically disabled readers who were shown to be unsuitable for the prescrip tion of Irlen lenses) were tested prior to intervention, at a posttest, and at a follow-up session 1 year later. Irlen lenses were found to have no effect either on reading performance or on any of the process variables thought to underlie reading ability.

Auditory inspection time, sustained attention, and the fundamentality of mental speed

Abstract This study investigates two interelated issues: (i) the view that mental speed is a fundamental property of the nervous system by assessing the relationship between inspection time (IT) tasks from two sensory modalities, and (ii) the feasibility of conceptualizing the well-known IT-ability relationship in terms of both IT and ability tasks requiring sustained attention. Subjects ( N = 78) undertook a pitch discrimination ability (PDA) task and constant and variable foreperiod (FP) IT tasks representing both auditory (AIT) and visual (VIT) modalities. AIT had little relationship to VIT but a close relationship to PDA, suggesting that the AIT procedure principally measures specific auditory abilities. Also, attentional load was found not to affect the IT-ability relationship, suggesting that sustained attention may not moderate the IT-ability relationship. Results are discussed in terms of the implications of the attentional findings and problems with the currently used AIT task.

Inspection time and the content of simple tasks: A framework for research on speed of information processing

Abstract Inspection time (IT) has been intensively investigated as an experimental correlate of IQ, but relatively few attempts have been made to analyse its cognitive content. Many writers have ignored the cautions expressed by the originators of IT and have treated it as the measure of a common. noncognitive or minimally cognitive, precursor to cognitive activity. An alternative concept of IT is offered which indexes the time taken for the processing required by specific experimental tasks. According to this view, correlations with cognitive ability measures are strongly influenced by the specific overlap ping content of the experimental task and the ability test. Rather than a fixed quantity that reflects the efficiency of the nervous system. IT can be seen as a suitable tool for analysing the cognitive content of different experimental tasks. This altemative view was tested in an experiment that varied the cognitive load of experimental tasks within an IT procedure, and that related verbal and nonverb...

Variations of the 2-line inspection time stimulus

Mackenzie and Bingham [(1985) Australian Journal of Psychology, 37, 257–268] used a variation of the 2-line Inspection Time (IT) task shifting the stimulus position between trials to prevent focussing of attention and obtained 71% thresholds which correlated -0.50 with WAIS Performance IQ. Nettelbeck [(1987) Speed of information-processing and intelligence. Norwood, NJ: Ablex] estimated the mean 97.5% threshold for Mackenzie and Binghams subjects was 262 msec where other Inspection Time studies obtain estimated 97.5% thresholds of around 100 msec, and suggested the higher mean threshold estimate might be due to the changes in stimulus position. This experiment investigates whether the higher thresholds obtained by Mackenzie and his associates are due to the changes in stimuli used. Fifty non-retarded adults served as subjects for: M, stimuli which changed position as in Mackenzie and Bingham (1985); S, stimuli similar to M presented in fixed position; and N, stimuli more similar to the conventional 2-line stimuli in contrast and mask width. There were no significant differences between the 3 stimuli in their mean thresholds or in their correlations with progressive matrices (mean r = -0.61). The mean 79% threshold of 90 msec converts to an estimated 97.5% threshold of 216 msec. It follows that changing stimulus position (M vs S) or stimulus contrast or mask width (S vs N) are not responsible for the higher estimated 97.5% thresholds. The present study has obtained for the whole sample a correlation between mean IT and intelligence, -0.61, which is significantly higher than Hunts [(1980) British Journal of Psychology, 71, 449–474] 0.3 barrier. Correcting possible skew in IT by log transform produces a correlation of -0.64, and there is no evidence that the correlation is substantially lower for subjects of above average IQ, after correcting for restriction of range r = -0.55.

Hypothesized genetic racial differences in IQ: A criticism of three proposed lines of evidence

Three lines of reasoning are discussed which have been put forward by A. R. Jensen in support of the hypothesis of genetic racial differences in IQ. These are the probabilistic connection of heritability to between-group genetic differences, the theoretical or formal relationship of within-group heritability to between-group heritability, and the regression of the IQ scores of blacks and whites to different population means. The first is shown to be a purely empirical claim that has no value as evidence in the absence of substantial confirming data, which are not available. The second and third are shown to be purely formal implications of the statistical models used to describe between-group heritability and linear regression, with no implications for the validity of the hypothesis. The attempted use of all three to support the hypothesis of genetic racial differences in IQ is discussed as an example of the fallacious reification of abstract methodology.

Partial reinforcement and extinction in vasomotor conditioning

In order to investigate cognitive versus traditional accounts of responding in extinction and the discrimination hypothesis for the partial reinforcement effect, 40 human subjects were randomly divided into two groups and were treated according to thermal vasomotor conditioning procedures using either 25 trials of continuous reinforcement or 100 trials of 25% partial reinforcement. At the onset of extinction, half of each group was given traditional noninformed extinction, while the other (informed) half had the thermal stimulator removed. The usual greater resistance to extinction was obtained after partial reinforcement than after continuous reinforcement in the two noninformed groups; however, immediate extinction of responding was obtained from the first extinction trial in the two informed groups. These results are consistent both with the discrimination hypothesis for the partial reinforcement extinction effect and with cognitive explanations of responding in extinction. Consequences for the behavioral therapies are discussed.