Sunday, 20 September 2015

Multiple objects, unitary ability?


Tracking multiple objects is one of the essential tasks at any conference, though the objects would prefer to be called distinguished researchers, which is what they are. Researchers, speakers, confederates, people who need to be persuaded about something, all swirl around the Barcelona conference room and the associated coffee spaces, with minimal supervision. I suppose, in the interests of keeping track on them, I could ask them to wear identifying hats. The task of tracking multiple targets must have been important in our hunter gatherer past, and so might be a candidate task for a dedicated module somewhere in the brain. I am a generalist rather than a modules man, but I make an exception for faces. (I never forget a face, but in your case I'll be glad to make an exception). I assume that the ability to track multiple objects is an advantage if one is shadowing people through city streets.

Jeremy Wilmer and colleagues have had a look at this, and believe they have identified that multiple object tracking is driven by a relatively specific cognitive mechanism that is not reducible to general ability.


Jeremy B Wilmer 1 , Ken Nakayama 2 , Laura Germine 3

1 Wellesley College,

2 Harvard University.

3 Massachusetts General Hospital.


Jeremy Wilmer

Though recent decades have seen massive improvements in our understanding of cognitive and neural mechanisms of behavior, the task of dissecting human ability into its basic cognitive and neural components has remained elusive (Deary, 2000, 2010).

Here, we examine a potential new tool for such dissection: multiple object tracking (MOT), the elementary cognitive task (ECT) of keeping track of several moving objects amongst moving distractor objects. MOT’s neural substrates have been well characterized (Jovicich et al., 2001) and the bulk of reliable individual differences in MOT can be explained by a single posterior event-related potential (ERP) component (Drew & Vogel, 2008). Yet of the 145 papers on MOT to date, only one other has examined individual diferences (Oksama & Hyona, 2004).

Our aim was to characterize the cognitive correlates of MOT. To this end, we developed a brief (8-10 min), reliable (Cronbach’s alpha = .88), web-based measure of MOT performance. We posted this test and several others on our website, which has succeeded in sustainedly attracting a large number of motivated volunteer participants (~1.5 million since 2008) by providing engaging tests that give performance feedback.

We tested a total of 19,724 participants (10,014 male) of varying ages (5th, 50th, and 95th percentiles 14, 25, and 58 years, respectively), educations (e.g. 34% of 25+ year olds had no more than a high school diploma), and ethnicities (46% non-European). MOT dissociated strongly from reliable (Cronbach’s alpha > .80), well-validated tests of sustained visual attention (r(1930)=-.03) and vocabulary (r(2810)=-.09), evidence that individual differences in MOT performance are driven by a relatively specific cognitive mechanism that is not reducible to a single general ability. MOT associated strongly with reliable (Cronbach’s alpha > 0.80), well-validated tests of spatial working memory (r(10841)=.44) and rapid spatial attentional switching (r(533)=.41), evidence that MOT captures a mechanism important for visuospatial performance.

Finally, MOT robustly predicted SAT-math performance (r(2467)=.29), but less so SAT-verbal performance (r(2467)=.09), evidence for a relatively specific link of MOT performance to math potential. Here, we report a study of MOT that is nearly two orders of magnitude larger than the entire prior literature on MOT.

Our results demonstrate that individual differences in MOT can be reliability and validly measured. We develop, norm, and validate a brief, reliable, new web-based test of MOT. By characterizing several key cognitive correlates of (and dissociations from) MOT, we place MOT firmly in a broader framework of human abilities. Given advances in our understanding of the neural correlates of MOT, we suggest that MOT could aid future efforts to dissect human ability into its core neuro-cognitive components.

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