Infants’ sense of approximate numerosity: Heritability and link to other concurrent traits

The ability to perceive approximate numerosity is present in many animal species, and emerges early in human infants. Later in life, it is moderately heritable and associated with mathematical abilities, but the etiology of the Approximate Number System (ANS) and its degree of independence from other cognitive abilities in infancy is unknown. Here, we assessed the phenotypic specificity as well as the influence of genetic and environmental factors on the ANS in a sample of 5-month-old twins (N = 514). We found a small-to-moderate but statistically significant effect of genetic factors on ANS acuity (heritability = 0.18, 95% CI: 0.02, 0.33), but only when differences in numerosity were relatively large (1:4 ratio). Non-verbal ability assessed with the Mullen Scales of Early Learning (MSEL) was found to be heritable (0.47; 95% CI: 0.34, 0.57) and the phenotypic association between ANS acuity and non-verbal ability performance was close to zero. Similarly, we found no association between ANS acuity and general attention during the task. An unexpected weak but statistically significant negative association between ANS acuity and scores on the receptive language scale of the MSEL was found. These results suggest that early ANS function may be largely independent from other aspects of non-verbal development. Further, variability in ANS in infancy seems to, to some extent, reflect genotypic differences in the population.

Highlights

• Assessing 514 infant twins with eye tracking, we found that infants' sense of approximate numerosity is heritable and not positively associated with concurrent attentional, cognitive or motor abilities.
• These results have implications for our understanding of development of mathematical ability and the link between cognitive abilities early in postnatal life.

     

Assertion and transparent self-knowledge

ABSTRACT

We argue that honesty in assertion requires non-empirical knowledge that what one asserts is what one believes. Our argument proceeds from the thought that to assert honestly, one must follow and not merely conform to the norm ‘Assert that p only if you believe that p’. Furthermore, careful consideration of cases shows that the sort of doxastic self-knowledge required for following this norm cannot be acquired on the basis of observation, inference, or any other form of detection of one’s own doxastic states. It is, as we put it, transparent rather than empirical self-knowledge.