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

Abstract

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.

Genetic and environmental contributions to gaze lateralization across social and non-social stimuli in human infants

“…The stimuli used in this study (Non-social condition 36 ; Social condition 37 ; Mixed condition 38 ) were not purposefully designed to measure gaze lateralization, but were used for this purpose as we believe they fulfil the characteristics necessary to answer our research questions. In all three conditions, the sample is based on the same set of infants from BATSS 35 , although the sample varies slightly in each condition due to stimuli-specific exclusion criteria (see specifications in each condition section).…”

“…2 ). The primary goal of these stimuli was to measure the approximate number system (already published data 36 ). Each image was unique in terms of a specific spatial constellation of dots.…”

“…each image consisted of two sets of dots that was presented for 500 ms, followed by a blank screen for 300 ms. Every other image showed identical sets of dots on the right and left side the screen while remaining images differed in numerosity on the two sides. Reproduced with permission from authors 36 . …”

Improving accuracy and precision of heritability estimation in twin studies: Reassessing the measurement error assumption

“…Data aggregation is a common practice in heritability estimation. Examples can be found in the fields of psychometrics (e.g., Rea-Sandin et al, 2023; ; Hung et al, 2023; Gustavson et al, 2023; Vellani et al, 2022; Viktorsson et al, 2022; Yeom et al, 2022; Wang et al, 2020; Routledge et al, 2018; Stins et al, 2005; Schachar et al, 2010; Fan et al, 2001) and neuroimaging (Kastrati et al, 2022; van Drunen et al, 2021; Chen et al, 2019; Harper et al, 2019; van der Meulen et al, 2018; Anokhin et al, 2017; Blokland et al, 2011; Matthews et al, 2007; Polk et al, 2007). This practice is also popular in test-retest reliability estimation in psychometrics (e.g., Hedge et al, 2018) and neuroimaging (e.g., Elliott et al, 2020).…”