Where do cognitive limitations come from and why do we care? The divergent cases of visual working memory storage and approximate number sense acuity

At any given moment, the mind is constrained by certain fundamental limits. Research on Visual Working Memory (VWM) storage capacity and Approximate Number Sense (ANS) acuity has emphasized the identification of independent behavioral and neural signatures. But where do an individual's limits come from? Are they shaped by the same or different factors? And what relevance do these limits have - jointly or independently - for everyday life? Here, in a single sample of 430 monozygotic (MZ) and 238 dizygotic (DZ) twin individuals, we investigate heritability, age curves, and practical correlates for both VWM storage and ANS acuity. We intentionally designed our VWM storage and ANS acuity tasks to be perceptually identical on a moment-to-moment basis (indistinguishable over any 0.7 given second period), differing critically in their cognitive demands. Despite this task similarity, we found strikingly divergent results. First, VWM storage was highly (67%) heritable whereas ANS acuity was even more highly (100%) environmental, suggesting nearly independent etiological factors. Second, we found about a decade difference between the ages of peak performance: VWM storage peaked relatively early at age ~20, whereas ANS acuity peaked later at age ~30 (the latter is consistent with Halberda et al, 2011, PNAS). Third, while both measures were predictive of validated self-report measures of math and science skills, VWM storage was more predictive for both math skills, R2=.07, F(1,666)=48.90, p< .001, and science skills, R2=.06, F(1,666)=38.72, p< .001, compared to ANS acuity (R2=.03, F(1,666)=23.52, p< .001 and R2=.02, F(1,666)=16.44, p< .001, respectively). Moreover, most of the predictive power for VWM storage was independent of ANS accuracy, and (to a lesser extent) vice versa. These results suggest a strikingly independent story of etiological origins and everyday importance for two core cognitive limitations. Meeting abstract presented at VSS 2017