Meta-analysis of the relationship between intelligence and inspection time

This study replicated and extended Kranzler and Jensen's [Intelligence 13 (1989) 329] meta-analysis of the relationship between inspection time (IT) and intelligence (IQ). Separate meta-analyses were conducted on obtained correlations (r's) between IT and general IQ for the total sample and for studies using samples of adults and children. Two new meta-analyses were also conducted. The first compared the IT–IQ r between visual and auditory IT; the second compared the r between strategy users and nonusers. For the total sample (N>4100), the r was −.51 after correction for artifactual effects (−.30 prior to correction). No statistically significant difference was observed between the mean corrected r of −.51 for adults and −.44 for children. The mean corrected r for visual and auditory IT measures were −.49 and −.58, respectively, suggesting that the relationship between IT and IQ is comparable across type of IT task. The mean corrected r of −.77 for strategy nonusers was statistically significantly higher than the r of −.60 for strategy users. Implications of these findings for future research are discussed.     

Inspection time and its relation to intelligence

Inspection time, defined as the minimum duration for which two different stimuli must be presented if they are to be perceived as different, was measured for both auditory and visual stimuli. The minimum durations were determined by means of a two- alternative forced-choice task for 50 children whose average age was 12 years 2 months. The times were correlated with the children's verbal (Mill-Hill vocabulary) and nonverbal (Raven matrices) intelligence. The Kendall correlation coefficients were ?.3188 and ?.0929 for the auditory and visual inspection times with verbal intelligence, and ?.2322 and ?.2676 for those times with nonverbal intelligence. Auditory and visual inspection times were correlated .1721 with each other. These results do not support earlier claims that inspection time is closely related to conventional measures of intelligence.     

Clocking g: Relating intelligence and measures of timed performance

The relationships between intelligence test scores and measures derived from reaction time (RT) and perceptual speed procedures were investigated in 137 twelve-year-old students with IQs ranging from 59 to 142. A range of intelligence tests were used and the scores factor analyzed to produce general, spatial and verbal factors. Test and factor scores were correlated with perceptual speed and with measures taken from 2, 4, and 8 choice RT tasks using a response keyboard upon which the subject's fingers directly rested, thus avoiding interpretive problems associated with a “home key.” Inspection time correlated poorly with intelligence. Only three of the RT measures produced correlations greater than .25 with the general factor. These were the slope of Hick's law, B, (correlation −.28), the 8 choice mean RT, RT8, (−.33) and the 8 choice standard deviation, SD8 (−.41), compared with the average intercorrelation between the intelligence measures of .40. Test-retest correlations of the RT measures, taken over a year for half the subjects, were low as reliability measures, with .35 for B, .52 for RT8, and .48 for SD8. Correlations of RT measures with spatial scores were not significantly greater than with verbal scores, suggesting that whatever relationship exists is with a general factor rather than only a spatial one.     

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.     

Inspection time and the relationship among elementary cognitive tasks, general intelligence, and specific cognitive abilities

The relationship between inspection time (IT) and paper-and-pencil tests of cognitive ability is well documented. However, the extent to which IT relates to cognitive ability through general intelligence or through group factors such as performance has not been fully addressed. Another unresolved issue is whether IT relates to psychometric intelligence independent from other elementary cognitive tasks. The current study examined these issues in a sample of 6–13-year-old twins drawn from the Western Reserve Twin Project (WRTP) (n=568 participants). Analyses suggest that IT and other elementary tasks predict general intelligence. IT also predicts Performance ability while other elementary tasks do not. Furthermore, IT contributes variance to cognitive ability independent from other elementary tasks. These suggest that multiple indices of elementary cognitive ability are necessary to fully understand their relationship with complex psychometric measures.     

儿童的检测时与智力

采用三种视觉检测时任务,考察了儿童的检测时的特点以及儿童的检测时与智力之间的关系。结果发现：随着年龄的增长,儿童的检测时有逐步减小的趋势;儿童的检测时依赖于加工任务的类型。儿童的检测时与智力测验分数之间具有中等程度的负相关,并且两者之间的相关程度受加工任务和年龄因素的影响;与检测时快的儿童组相比,检测时慢组的检测时能够更好预测其智力测验分数。     

Exploring possible neural mechanisms of intelligence differences using processing speed and working memory tasks: An fMRI study

To explore the possible neural foundations of individual differences in intelligence test scores, we examined the associations between Raven's Matrices scores and two tasks that were administered in a functional magnetic resonance imaging (fMRI) setting. The two tasks were an n-back working memory (N = 37) task and inspection time (N = 47). The subjects were members of the Aberdeen Birth Cohort 1936, aged in their mid–late 60s when tested for this study. Performance on both tasks was correlated significantly with scores on Raven's Matrices. In the inspection time task there were regions with significant correlations between the neural activity (BOLD response) and performance but not between BOLD response and scores on Raven's Matrices. In the working memory task there were no significant correlations between BOLD response and either performance or scores on Raven's Matrices. Moreover, there was almost no mediation of the Raven's Matrices versus n-back and inspection time scores correlations by the respective BOLD response. These findings partially replicate important aspects of a prominent report in this field [Gray, J.R., Chabris, C.F., & Braver, T.S. (2003). Neural mechanisms of general fluid intelligence. Nature Neuroscience, 6, 316–322.], but have also extended the those finding into both a unique population and a novel functional task.     

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.     

Psychoacoustic abilities as predictors of vocal emotion recognition

Prosodic attributes of speech, such as intonation, influence our ability to recognize, comprehend, and produce affect, as well as semantic and pragmatic meaning, in vocal utterances. The present study examines associations between auditory perceptual abilities and the perception of prosody, both pragmatic and affective. This association has not been previously examined. Ninety-seven participants (49 female and 48 male participants) with normal hearing thresholds took part in two experiments, involving both prosody recognition and psychoacoustic tasks. The prosody recognition tasks included a vocal emotion recognition task and a focus perception task requiring recognition of an accented word in a spoken sentence. The psychoacoustic tasks included a task requiring pitch discrimination and three tasks also requiring pitch direction (i.e., high/low, rising/falling, changing/steady pitch). Results demonstrate that psychoacoustic thresholds can predict 31% and 38% of affective and pragmatic prosody recognition scores, respectively. Psychoacoustic tasks requiring pitch direction recognition were the only significant predictors of prosody recognition scores. These findings contribute to a better understanding of the mechanisms underlying prosody recognition and may have an impact on the assessment and rehabilitation of individuals suffering from deficient prosodic perception.     

Correlation between inspection time and psychometric abilities: A personal interpretation

More than 25 years of research suggests that the measure inspection time (IT) does capture low-level aspects of cognitive functioning that contribute to human intelligence. However, recent evidence does not support earlier claims that IT estimates the speed of a single mechanism like “sampling input” or “apprehension.” Rather, together with other tasks that employ pattern backward masking to limit the duration for which information is available for processing, IT is probably sensitive both to focused attentional capacities to detect organization and change under severe time constraints and to decision processes, ongoing beyond mask onset, that monitor responding. Among normal young adults, IT is correlated with the broad psychometric factor Gs (“speediness”). This mediates correlation with general intelligence. In this group, IT is not correlated with Gf. However, whether this outcome generalizes to samples of persons with an intellectual disability, to young children, or to elderly persons is not yet known. Psychological processes underpinning IT are currently only speculatively defined, but it should prove possible to unravel these by experimentation. To this end, backward masking procedures are arguably more theoretically tractable than reaction time tasks because they reduce the impact of higher-level cognitive strategies on performance. On this basis, IT may hold promise as a means for developing partial explanations for intelligence in psychological terms. However, whether this is realized depends on identifying the psychological functions that support IT.     

Placing inspection time, reaction time, and perceptual speed in the broader context of cognitive ability: The VPR model in the Lothian Birth Cohort 1936

The idea that information processing speed is related to cognitive ability has a long history. Much evidence has been amassed in its support, with respect to both individual differences in general intelligence and developmental trajectories. Two so-called elementary cognitive tasks, reaction time and inspection time, have been used to compile this evidence, but most studies have used either one or the other. Relations between speed and fluid intelligence have tended to be stronger than those between speed and crystallized intelligence, but studies testing this have confounded verbal abilities with crystallized intelligence and spatial/perceptual abilities with fluid intelligence. Questions have also been raised regarding whether speed contributes directly to general intelligence or to more specific cognitive abilities to which general intelligence also contributes. We used 18 ability and speed measures in the Lothian Birth Cohort 1936, assessed at approximately age 70, to construct alternative versions of the Verbal-Perceptual-Image Rotation (Johnson & Bouchard, 2005a) model of cognitive ability to test different hypotheses regarding these issues. Though differences in the extents to which our models fit the data were relatively small, they suggested that reaction and inspection time tasks were comparable indicators of information processing speed with respect to general intelligence, that verbal and spatial abilities were similarly related to information processing speed, and that spatial, verbal, and perceptual speed abilities were more directly related to information processing speed than was general intelligence. We discuss the theoretical implications of these results.     

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.     

Cross-modal facilitation in speech prosody

Speech prosody has traditionally been considered solely in terms of its auditory features, yet correlated visual features exist, such as head and eyebrow movements. This study investigated the extent to which visual prosodic features are able to affect the perception of the auditory features. Participants were presented with videos of a speaker pronouncing two words, with visual features of emphasis on one of these words. For each trial, participants saw one video where the two words were identical in both pitch and amplitude, and another video where there was a difference in either pitch or amplitude that was congruent or incongruent with the visual changes. Participants were asked to decide which video contained the sound difference. Thresholds were obtained for the congruent and incongruent videos, and for an auditory-alone condition. It was found that the congruent thresholds were better than the incongruent thresholds for both pitch and amplitude changes. Interestingly, the congruent thresholds for amplitude were better than for the auditory-alone condition, which implies that the visual features improve sensitivity to loudness changes. These results demonstrate that visual stimuli can affect auditory thresholds for changes in pitch and amplitude, and furthermore support the view that visual prosodic features enhance speech processing.     

Convergence between attention variables and factors of psychometric intelligence in older adults

The purpose of the present study was to examine the hypothesis that individual differences on measures of attention would converge with select factors of psychometric intelligence, especially fluid intelligence and short-term acquisition and retrieval. A sample of 83 elderly adults $\text{(}\text{X}\text{= 71}\text{years}\text{)}$ was administered a battery of 17 psychometric ability tests. Tests were selected to mark four psychometric ability factors (Cattell and Horn's dimensions of fluid and crystallized intelligence, short-term acquisition and retrieval, and perceptual speed). Also, seven tasks representing four aspects of attention—decoding processes, selective attention, attention switching, and concentration—were administered. A confirmatory factor analysis was conducted to examine the relationships among the four psychometric ability factors and 11 variables obtained from the attention tasks. Results were only partially consistent with the hypothesized pattern of convergence. Two attention measures had significant loadings on a fluid-type intelligence factor, and one had a marginally significant loading on a short-term memory factor. In general, the greatest convergence occured between attention variables and the ability factor of Perceptual Speed. Results were discussed with respect to previous research on psychometric abilities and cognitive processes, the theory of fluid-crystallized intelligence, and their implications for understanding intellectual aging.     

Pitch direction ability predicts melodic perception in autism

Individuals with autism spectrum disorders (ASDs) often present atypical auditory perception. Previous work has reported both enhanced low-level pitch discrimination and superior abilities to detect local pitch structure on higher-level melodic tasks in ASD. However, it is unclear how low and high levels of auditory perception are related in ASD or typical development (TD), or how this relationship might change across development and stimulus presentation rates. To these aims, in the present study, children with ASD and TD were tested on a low-level pitch direction discrimination task and a high-level melodic global-local task. Groups performed similarly on both of these auditory tasks. Moreover, individual differences in low-level pitch direction ability predicted performance on the higher-level global-local task, with a stronger relationship in ASD. Age did not affect the relationship between low-level and high-level pitch performance in either ASD or TD. However, there was a more positive effect of age on the high-level global-local task performance in TD than ASD. Finally, there was no effect of stimulus rate on the relationship between low-level and high-level pitch performance in either group. These findings provide a better understanding of how perception is associated across levels of processing in ASD versus TD. This work helps to better understand individual differences in auditory perception and to refine ASD phenotypes.     

Auditory imagery and the poor-pitch singer

The vocal imitation of pitch by singing requires one to plan laryngeal movements on the basis of anticipated target pitch events. This process may rely on auditory imagery, which has been shown to activate motor planning areas. As such, we hypothesized that poor-pitch singing, although not typically associated with deficient pitch perception, may be associated with deficient auditory imagery. Participants vocally imitated simple pitch sequences by singing, discriminated pitch pairs on the basis of pitch height, and completed an auditory imagery self-report questionnaire (the Bucknell Auditory Imagery Scale). The percentage of trials participants sung in tune correlated significantly with self-reports of vividness for auditory imagery, although not with the ability to control auditory imagery. Pitch discrimination was not predicted by auditory imagery scores. The results thus support a link between auditory imagery and vocal imitation.     

Time Perception: Modality and Duration Effects in Attention-Deficit/Hyperactivity Disorder (ADHD)

Time perception performance was systematically investigated in adolescents with and without attention-deficit/hyperactivity disorder (ADHD). Specifically, the effects of manipulating modality (auditory and visual) and length of duration (200 and 1000 ms) were examined. Forty-six adolescents with ADHD and 44 controls were administered four duration discrimination tasks and two control tasks, and a set of standardized measures. Participants with ADHD had higher thresholds than controls on all of the duration discrimination tasks, with the largest effect size obtained on the visual 1000 ms duration discrimination task. No group differences were observed on the control tasks. Visual–spatial memory was found to be a significant predictor of visual and auditory duration discrimination at longer intervals (1000 ms) in the ADHD sample, whereas auditory verbal working memory predicted auditory discrimination at longer intervals (1000 ms) in the control sample. These group differences suggest impairments in basic timing mechanisms in ADHD.     

Relationships between three auditory inspection time tasks and processing speed

This study investigated the relationship between a spatial auditory inspection time task and previous versions of AIT, as well as the relationships of these tasks with visual inspection time (VIT) and general speediness (Gs). A total of 96 university undergraduates (age mean (M) = 20.0 years, standard deviation (SD) = 4.0 years) completed three AIT tasks, VIT, auditory reaction time (ART) and visual reaction time (VRT), and two Gs marker tests. Auditory inspection time‐spatial (AIT‐S) did not relate to VIT, but it did relate to the Gs marker tests. It also loaded moderately on a Gs factor along with VIT. Neither of the alternate AIT tasks showed any consistent relationships to reaction time (RT) or Gs measures. The AIT‐S task did, however, share substantial variance with its predecessors, suggesting that performance on all AIT tasks relies to some extent on similar processes. Further research is required to determine the nature of these processes.     

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.     

Power and speed components of individual differences in letter matching

Several previous studies have reported a correlation (typically around −.30) between standardized verbal ability test scores and name identity minus physical identity reaction times (NI-PI) in a letter-matching task. This correlation has usually been thought to reflect the mutual dependence of both measures on long-term memory access time. The present research was designed to assess Carroll's (1981) suggestions that: (a) NI — PI may not be the optimal formula for predicting standardized test scores from letter matching data, and (b) NI — PI may actually be related to the speed rather than the power component of standardized tests. Fifty-one subjects previously tested with a standardized reading test participated in letter-matching and word-reading tasks. The latter tasks required subjects to read words and specially constructed pseudowords. Power and speed measures were derived from the word-reading tasks and the standardized test on theoretical grounds (and supported by a principal components analysis). The results supported both of Carroll's contentions. NI — PI reaction time was related more to speed than power and the NI — PI statistic (as usually used) was not the optimum formula for predicting standardized test scores.