Saturday 19 September 2015

Hick’s Law, reaction times and fluid g

I would be proud to have submitted any of the papers presented at ISIR15. Here is one I was initially tempted to skip over, because I know you are busy people, running the world and inventing stuff. However, on closer inspection it reminds me of what I imagined in would do in psychological research, but never got round to, what with one thing and another.

I should talk about this at more length another time, when I do not have a press of papers to tell you about, but if psychology is to progress it must tackle some fundamental problems. In a reaction time experiment, what is the effect of response uncertainty, such as choosing between 2 or 4 options?

Hick (1952) On the rate of gain of information. Quarterly Journal of Experimental Psychology Volume 4, Issue 1, 1952

The principal finding is that the rate of gain of information is, on the average, constant with respect to time, within the duration of one perceptual-motor act, and has a value of the order of five “bits” per second.

I suggest you forget about contingent negative variation for the time being.


1 University of Utah,

A large body of research has examined correlations between reaction time (RT) and intellectual ability, though the neural correlates of that relationship and its potentially moderating task effects are comparatively understudied. Markers of anticipatory neural activity such as the EEG Contingent Negative Variation (CNV) represent compelling possible mediators of RT-ability relations, and provide a means to study neural processes that may drive task-specific effects.

The goal of this study was to assess the effect of increasing numbers of response alternatives on CNV amplitudes preceding RT, and to evaluate relations therein to fluid intelligence (Gf). Forty-three, right-handed, undergraduate psychology majors were administered the WAIS-IV and performed a version of the Hick paradigm during EEG recording. The Perceptual Reasoning Index served as the measure of Gf. The Hick paradigm consisted of 96 trials each of simple, 2-choice, and 4-choice RT conditions, which were randomized within blocks. Each trial involved a cue indicating the condition, followed by a warning stimulus, a variable inter-stimulus interval (range 1-2.4 sec.), and a reaction stimulus.

Participants responded with their right hand. EEG data were epoched time-locked to the onset of the warning stimulus. CNVs were quantifed as the average amplitude from 875-1000 msec. post-stimulus at the central electrode Cz, and neighboring left (C3) and right-central electrodes (C4).

RT increased while CNVs generally decreased as a function of increasing response alternatives. Linear and quadratic trends were significant for both variables, indicating a smaller condition effect between the choice RT conditions. CNVs were larger overall at Cz relative to C3 and C4. Tis efect interacted with condition where activation decreased from simple to choice RT at Cz and C3, with no condition effect at C4. Gf significantly predicted overall, 2, and 4-choice RT (r ≥ -.36, p < .02), and the latter effects were significantly stronger than that for simple RT (z ≥ -2.0, p < .05).

Last, in the 4-choice condition, CNVs showed differential effects such that only C4 activation predicted RT (r = .41, p =.006), whereas only Cz showed a trend toward predicting Gf (r = -.29, p = .06). RT and anticipatory neural activation showed similar effects of increasing response alternatives. Detrimental trends of increasing alternatives on both RT and CNVs were negatively accelerated, indicating a larger difference between simple and choice RT than between different numbers of choice alternatives. The study also replicated findings of stronger RT-ability relations for choice than simple RT (e.g., Deary, Der, & Ford, 2001), but suggested complex effects on CNVs.

Taken together, the results suggest that identifying the mechanisms involved in simple vs. choice RT performance may help shed light on the neural substrates of RT-ability relations. Follow-up analyses of response-locked trials will clarify the time course and topography of activation most central to variation in RT and Gf.

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