Monday, June 29, 2009

Temporal g or temporal resolution power hypothesis: IQ Brain Clock support

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Temporal g...or...the temporal resolution power hypothesis (TRP). Lets hear it for the IQ Brain Clock!

I've previously blogged, with considerable excitement, about recent research that has suggested that the temporal resolution of one's internal "brain clock" may be more closely associated with intelligence scholars search for the neural underpinnings of general intelligence (g). Traditionally, and overwhelmingly, intelligence scholars have studied and focused on mental reaction time, largely based on the seminal work of Arthur Jensen. Then, along came recent research led primarily by mental timing scholar Rammsayer and colleagues...research that suggested that temporal g (vs. reaction time g) may be more important in attempts to identify the underlying mechanism of neural efficiency.. the focus of the search for the "holy grail" of general intelligence for decades.

The following just published journal article continlues to add to the evidence that temporal processing, temporal g, and/or temporal resolution, may be critically important in understanding human intellectual performance. Below is the article reference, abstract, and my paraphrased comments from a reading of the article.
  • Troche, S & Rammsayer, T. (2009). Temporal and non-temporal sensory discrimination and their predictions of capacity-and speed-related aspects of psychometric intelligence. Personality and Individual Differences,47, 52–57

The temporal resolution power hypothesis explains individual differences in psychometric intelligence in terms of temporal acuity of the brain. This approach was supported by high correlations between temporal discrimination and psychometric intelligence. Psychometric intelligence, however, was frequently found to be related to non-temporal discrimination (e.g., frequency, intensity, brightness discrimination). The present study investigated 100 female and 100 male participants with the aim to elucidate the functional relations between psychometric intelligence and temporal and non-temporal discrimination ability. Supporting the assumption of dissociable mechanisms, non-temporal discrimination predicted directly capacity – but not speed-related aspects of psychometric intelligence whereas temporal discrimination predicted both aspects. A substantial correlation between temporal and non-temporal discrimination suggested that general discrimination ability might account for the relations of psychometric intelligence to temporal and non-temporal discrimination abilities. Findings point to an internal structure of general discrimination ability with some dimensions of discrimination more predictive to certain aspects of psychometric intelligence than others.
Introduction/background summary

The neural efficiency hypothises, based on Jensen's model of neuronal oscillations, has stood front and center as the defacto explanation of individual differences in processing speed and psychometric intelligence. This model suggestes that individuals differ in the rate of rate of oscillation between refractory and excitatory states of neurons. The efficieny of oscillation rate, in turn, determines the speed/efficiency of transmission of neurally encoded information. The bottom line is that individuals with higher neural oscilate rates are believed to process information more efficiently, which leads to better intellectual performance.

In contrast, according to the articles authors, the more recent "temporal resolution power (TRP) hypothesis also refers to a hypothetical oscillatory process in the brain to account for the relationship between efficiency and speed of information processing as well as psychometric intelligence (Rammsayer & Brandler, 2002, 2007). According to this view, higher neural temporal resolution leads to faster information processing and to better coordination of mental operations resulting in better performance on intelligence tests. Rammsayer and Brandler (2002) proposed that psychophysical timing tasks, assessing temporal sensitivity and timing accuracy, are the most direct behavioral measures of TRP. The TRP hypothesis has been supported by subsequent studies which found substantial correlations between psychometric intelligence and timing performance (Helmbold, Troche, & Rammsayer, 2006, 2007; Rammsayer & Brandler, 2007)." Most of these studies have been described previously at the IQ Brain Clock blog under the label temporal g.

An important issue for the TRP hypothesis to address is the fact that the most frequently used mental timing tasks also imply some form of simple sensory discrimination (together with the timing component). In order for the TRP hypothesis to have merit, the model must address (explain) the established relation between sensory discrmination and psychometric (tested) intelligence not only for the temporal domain but also for other non-temporal sensory dimensions. As summarized by the author, "associations with psychometric intelligence were shown for color (r = .08 to r = .32; Acton & Schroeder, 2001), pitch (r = .42 to r = .54; Raz, Willerman, & Yama, 1987), or texture and shape in the tactile modality (r = .08 to r = .29; Stankov, Seizova-Cajic´, & Roberts, 2001)."

Purpose of study

The purpose of the current study was to disentagle the relations between temporal processing and sensory discrmination via the evaluation and testing of two different structural models. As described by the authors, "the first model expanded the investigation of Helmbold et al. (2006) to the level of latent variables by factorizing various non-temporal and temporal discrimination tasks. It is assumed that temporal and non-temporal discrimination abilities predict psychometric intelligence as two dissociable factors which, however, can be related to each other. The TRP hypothesis postulates that TRP affects both capacity- and speed-related aspects of psychometric intelligence (Helmbold & Rammsayer, 2006)."

Alternatively "Model 2 proceeds from Spearman’s (1904) assumption that a general discrimination ability predicts psychometric intelligence. In accordance with this view, temporal discrimination constitutes a factor indissociable from non-temporal discrimination. In other words, temporal and non-temporal discrimination tasks build a common factor referred to as GDA."

Method summary

The subjects were 100 male and 100 female volunteers (18 to 30 years of age; mean ± SD = 22.2 ± 3.3 years). The sample comprised 93 university students, 89 vocational school students and apprentices, while the remaining participants were working individuals of different professions. All participants reported normal hearing and normal or corrected-to-normal sight. The authors employed structural equation modeling (SEM) methods to evaluate and compare the two models.

Capacity and speed components of psychometric IQ (g) were measured with 12 subtests of the Berlin model of intelligence structure (BIS) test (Jäger, Süß, & Beauducel, 1997). Four temporal (temporal generalization, duration, temporal-order judgment, rhythm perception) and three non-temporal sensory discrimination tasks (pitch discrimination, intensity discrimination, rightness discrimination) were used to operationally define temporal processing and sensory discrimination, respectively.

Conclusions/discussion summary (emphasis added by blogmaster)

Evaluation and comparison of the two models suggested the following conclusions (as per the authors)
  • The relation between non-temporal discrimination and speed was completely mediated by temporal discrimination. The association between temporal discrimination and capacity was twofold. There was a weak but reliable direct association as well as a stronger indirect relation mediated by non-temporal discrimination.
  • Although Model 1 revealed a high correlation between temporal and non-temporal discrimination, the different relations of temporal and non-temporal discrimination to speed and capacity suggest that the two factors are dissociable. Our finding of a strong correlational link between temporal discrimination ability and psychometric intelligence is in line with the outcome of previous studies investigating the TRP hypothesis...according to this account, higher TRP entails increased speed and efficiency of information processing resulting in higher scores on both speed- and capacity-related intelligence tests. Thus, our finding that Model 1 fitted the data well is in line with the TRP hypothesis.
  • The present results corroborate Helmbold and Rammsayer’s (2006) finding of a stronger relationship between temporal discrimination ability and capacity compared to speed. On the contrary, shared variance with non-temporal discrimination accounted for the association between capacity and temporal discrimination whereas the direct link between temporal discrimination and capacity was rather weak. Thus, the strong relation between TRP and psychometric intelligence is probably due to the fact that TRP, when measured as a factor derived from temporal discrimination tasks, taps both temporal and unspecific discrimination abilities. From this perspective, time-related aspects of TRP may account for the association to speed whereas rather unspecific discrimination-related aspects mainly account for the association with capacity.
  • The more parsimonious Model 2 should be preferred over Model 1. Model 2 suggests that temporal and non-temporal discrimination tasks constitute a common factor of unspecific, general discrimination performance referred to as GDA. The close association between this factor and psychometric intelligence is supported by the outcome of previous studies.
  • The finding, that both temporal and non-temporal discrimination share a common source, supports the notion that general discrimination ability is somehow associated with higher-order mental ability.
  • The finding of a close association between GDA and psychometric intelligence suggests, that already at a very early sensory stage of information processing, higher neural efficiency can be observed as a correlate of psychometric intelligence
  • The high correlations between GDA and speed- as well as capacity-related aspects of psychometric intelligence, as revealed by Model 2, emphasize the importance of sensory performance as a correlate of higher-order mental ability. Nevertheless, differential relations between temporal and non-temporal discrimination and aspects of psychometric intelligence, as suggested by Model 1, may help to elucidate the internal structure of GDA. This is, certain sensory processes appear to be more predictive for certain aspects of psychometric intelligence than others. Such a conclusion is in line with the results of Stankov et al. (2001) who reported differential relations between cognitive abilities and aspects of tactile and kinesthetic perceptual processing. In the face of the available data, mapping of differential relationships between distinct sensory performances and components of psychometric intelligence represent a promising strategy to further explore the significance of sensory processes for human mental abilities.

Bottom line: This study continues to support the importance of temporal g, temporal processing, or the TRP hypothesis in explaining neural efficiency, which in turn is believed to play a major role in facilitating better (higher) intellectual performance. Understanding the interal IQ Brain Clock, and interventions/treatements that may help "fine tune" the brain clock (increase its timing resolution), appears an important avenue to pursue both for theoretical and applied (cognitive enhancement interventions) research. To pat myself on the back, I've previously summarized the potential link between increased resolution of the brain clock and higher cognitive functioning in prior professinal presentations (click here to visit a SlideShare PPT show)

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