Speed matters, but not how you think: IQ & latent factors in reaction time

One of the more surprising findings to emerge from the intelligence literature is that an individual's ability to think in highly complex and abstract forms is related to speed in tasks as simple as "press the lighted button." Simple reaction time tasks like this have amazing predictive power for performance on much more elaborate tasks, leading some theorists to propose that such reaction time (RT) measures grossly index the integrity or speed of processing in a way that benefits all tasks.

Interestingly, the average speed on simple RT tasks is often not as predictive as other aspects of the RT distribution. In their new JEP:G paper on the topic, Schmiedek et al. describe the "worst performance rule" in which an individual's slowest reaction times are predictive of their short-term memory capacity, general intelligence, and processing speed (how quickly they can perform simple judgments).

Why might this be? Extraordinarily slow RTs may be a simple reflection of lapses in attention or goal maintenance. Thus the relative number of those lapses (or the time taken to recover from them) may be driving the relationship with complex task performance (where sustained attention and goal maintenance are clearly important).

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