A Maternal Influence on Reading the Mind in the Eyes Mediated by Executive Function: Differential Parental Influences on Full and Half-Siblings

BACKGROUND: Parent-of-origin effects have been found to influence the mammalian brain and cognition and have been specifically implicated in the development of human social cognition and theory of mind. The experimental design in this study was developed to detect parent-of-origin effects on theory of mind, as measured by the 'Reading the mind in the eyes' (Eyes) task. Eyes scores were also entered into a principal components analysis with measures of empathy, social skills and executive function, in order to determine what aspect of theory of mind Eyes is measuring. METHODOLOGY/PRINCIPAL FINDINGS: Maternal and paternal influences on Eyes scores were compared using correlations between pairs of full (70 pairs), maternal (25 pairs) and paternal siblings (15 pairs). Structural equation modelling supported a maternal influence on Eyes scores over the normal range but not low-scoring outliers, and also a sex-specific influence on males acting to decrease male Eyes scores. It was not possible to differentiate between genetic and environmental influences in this particular sample because maternal siblings tended to be raised together while paternal siblings were raised apart. The principal components analysis found Eyes was associated with measures of executive function, principally behavioural inhibition and attention, rather than empathy or social skills. CONCLUSIONS/SIGNIFICANCE: In conclusion, the results suggest a maternal influence on Eye scores in the normal range and a sex-specific influence acting to reduce scores in males. This influence may act via aspects of executive function such as behavioural inhibition and attention. There may be different influences acting to produce the lowest Eyes scores which implies that the heratibility and/or maternal influence on poor theory of mind skills may be qualitatively different to the influence on the normal range

Pearson correlations (<i>r</i>) between siblings for Eyes scores and Eyes scores adjusted by removing the low-scoring outliers (Eyes Adj >17).

<p>**Correlation is significant at the 0.01 level (2-tailed).</p><p>*Correlation is significant at the 0.05 level (2-tailed).</p><p>'Correlation is significant at the 0.1 level (2-tailed).</p><p>For each model, the two categories of sibling pairs are derived from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0023236#pone-0023236-t002" target="_blank">Table 2</a>. In each case, a possible fit (in bold) is indicated by the second correlation being less than the first.</p

Mean percentage DNA shared by full and half-siblings by chromosome type.

<p>Mean percentage DNA shared by full and half-siblings by chromosome type.</p

Correct responses to Eyes items in quartiles depending on how often they are correctly identified.

<p>Correct responses to Eyes items in quartiles depending on how often they are correctly identified.</p

Principal components 1 and 2 (loadings >0.4) from the principal components analyses of the Eyes, BIS, EQ and AQ subscale scores.

<p>*The EQ loading is negative because the subscales AS, C, SS and I are all measured in the opposite sense, i.e. high scores are associated with poor skills and low empathy.</p

Model-fitting statistics for Eyes and Eyes Adj testing Mendelian, maternal and X-linked maternal models of heritability.

<p>Abbreviations: A, genetic influences; C, shared environmental influences; E, non-shared environmental influences.</p><p>The best fitting models are in bold.</p

Predicted relative order of correlations between siblings by model of preferential gene expression.

<p>Higher numbers denote stronger correlation.</p><p>*Assuming random inactivation of one X in females. Maternal X expression without random inactivation is indistinguishable from Maternal autosomal expression. In the case of preferential paternal X expression without random inactivation, values for full and maternal brothers reflects the possibility of zero to full maternal X expression in the absence of a paternal X.</p

Path diagram (above) and parameter values (below) for model fitting.

<p><i>a</i> = covariance in additive genetics and <i>c</i> = covariance in shared environment between siblings. Values for <i>a</i> represent the strongest form of the model assumed.</p