If you are a regular reader of the IQ Brain Clock, you can probably guess that this Journal of Neuroscience article by Ullen et al. (2008; abstract below) has me excited! The literature reviewed and results hit on many constructs, hypothesis, ideas, etc. that I've presented at this humble blog re: the potential importance of mental/interval time-keeping (the IQ Brain Clock; temporal processing/g) and general intelligence.
A few sample comments from the authors (and the blogmaster) are featured below:
- Recent studies suggest that temporal discrimination and judgment tasks may correlate higher with g (general intelligence) than classic reaction time (RT) tasks, tasks that have, for decades, been considered the best available measures of the biological correlates of brain efficiency (see new, destined to be classic, book on the RT paradigm in intelligence research by A. Jensen--Clocking the Mind). "Neural factors influencing accuracy of timing may thus be fundamental to intelligence."
- Study limitation. I believe the use of a single measure for general intelligence (The Ravens Progressive Matrices), although a common practice, warrants some degree of caution. Some psychometric researchers equate performance on the RPM, which is a well established measure of fluid reasoning/intelligence (Gf), with g. I've read enough research that suggest that the Gf=g argument is not 100% established. So, IMHO, the current study may suggest a link between rhythmic abilities (and temporal processing) and Gf...not necessarily g. I'd like to see a similar study with a g measure comprised of a wide range of Gf-Gc (CHC) abilities, like that used in Rammsayer's temporal g research (which the current study reinforces).
- It is amazing that a simply isochronous tapping task (subjects listen to 20 auditory metronome clicks and then must continue the same beat, without the metronome, for 45 more beats) correlates with Gf. The authors concluded that "we demonstrate that intelligence is related to millisecond accuracy in isochronous tapping, a simple timing task that does not involve response selection or information processing of the type typically required in the elementary cognitive tasks (Deary, 2001) and in which interval-to-interval variability is primarily controlled by automatic processes."
- Consistent with prior posts and my IQ Brain Clock powerpoint presentations, it is exciting to find that these researchers confirm the importance of the prefrontal lobes. The authors conclude that "tapping variability and intelligence share neural substrates in the prefrontal white substance."
- General intelligence is correlated with the mean and variability of reaction time in elementary cognitive tasks, as well as with performance on temporal judgment and discrimination tasks. This suggests a link between the temporal accuracy of neural activity and intelligence. However, it has remained unclear whether this link reflects top-down mechanisms such as attentional control and cognitive strategies or basic neural properties that influence both abilities. Here, we investigated whether millisecond variability in a simple, automatic timing task, isochronous tapping, correlates with intellectual performance and, using voxel-based morphometry, whether these two tasks share neuroanatomical substrates. Stability of tapping and intelligence were correlated and related to regional volume in overlapping right prefrontal white matter regions. These results suggest a bottom-up explanation of the link between temporal stability and intellectual performance, in which more extensive prefrontal connectivity underlies individual differences in both variables.