Investigating heritability of laterality and cognitive control in speech perception Sebastian Ocklenburg a,⇑ , Felix Ströckens a , Josef J. Bless b , Kenneth Hugdahl b,d , René Westerhausen c , Martina Manns a a Institute of Cognitive Neuroscience, Biopsychology, Ruhr-University Bochum, Germany b Department of Biological and Medical Psychology, University of Bergen, Norway c Department of Psychology, University of Oslo, Oslo, Norway d NORMENT Center of Excellence, University of Bergen, Norway article info Article history: Received 11 March 2016 Revised 24 August 2016 Accepted 12 September 2016 Available online 16 September 2016 Keywords: Dichotic listening Language lateralization Handedness Genetics Family study Speech perception abstract Several studies analyzing the ontogenetic origin of cerebral lateralization provide evidences for a genetic foundation of handedness in humans that is modulated by environmental influences. Since other forms of behavioral lateralization are less investigated, it is unclear as to how far different functions display sim- ilar heritability. But deeper knowledge is necessary to understand if and how developmental coupling of different functions is based on a shared genetic background or on the impact of environmental influences. Here, we investigated the heritability of language lateralization assessed with the dichotic listening task, as well as the heritability of cognitive control processes modulating performance in this task. Overall, 103 families consisting of both parents and offspring were tested with the non-forced, as well as the forced- right and forced-left condition of the forced attention dichotic listening task, implemented in the iDichotic smartphone app, developed at the University of Bergen, Norway. The results indicate that the typical right ear advantage in the dichotic listening task shows weak and non-significant heritability (h 2 = 0.003; p = 0.98). In contrast, cognitive factors, like attention focus (forced right condition: h 2 = 0.36; p < 0.01; forced left condition: h 2 = 0.28; p < 0.05) and cognitive control (Gain forced right: h 2 = 0.39; p < 0.01; Gain forced left: h 2 = 0.49; p < 0.01) showed stronger and significant heritability. These findings indicate a variable dependence of different aspects of a cognitive function on heritability and implicate a major contribution of non-genetic influences to individual language lateralization. Ó 2016 Elsevier Inc. All rights reserved. 1. Introduction One of the most controversial topics in laterality research is the question, to what extent functional hemispheric asymmetries are heritable (Collins, 1975; Francks et al., 2007; McManus, Davison, & Armour, 2013; Ocklenburg, Beste, Arning, Peterburs, & Güntürkün, 2014; Ocklenburg, Beste, & Güntürkün, 2013; Rentería, 2012). For handedness, evidence from adoption (Carter- Saltzman, 1980) and twin studies (Ooki, 2014) convincingly suggests that it is at least partly controlled by genetic factors. Interestingly, different aspects of handedness seem to have differential heritability, since Lien, Chen, Hsiao, and Tsuang (2015) found that degree of handedness showed higher heritability than a hand-preference index and direction of handedness. This suggests that different functional neuronal systems are involved in determining these aspects, all of them having their own gene- dependent pattern. To this respect, it would be useful to compare heritability of handedness with other lateralized functions to understand which aspects are most likely under genetic control and which are influenced by environmental factors. A shared genetic background may cause developmental coupling of different lateralized functions. Unfortunately, for all other forms of laterality (such as lateralization of language, emotion or spatial abilities), experimental evidence supporting or disproving a relation of children’s and parent’s left-right preferences is extremely scarce. As a rare exception, Bryden (1975) published a study in which he used the dichotic listening task to investigate how language lat- eralization runs in families. Familial correlations in 49 families revealed somewhat puzzling results. While there was a significant positive correlation between the dichotic listening lateralization quotient (LQ) of mothers and offspring, no such relation was found http://dx.doi.org/10.1016/j.bandc.2016.09.003 0278-2626/Ó 2016 Elsevier Inc. All rights reserved. ⇑ Corresponding author at: Ruhr-Universität Bochum, Fakultät für Psychologie, Institut für Kognitive Neurowissenschaft, Abteilung Biopsychologie, Univer- sitätsstraße 150, 44780 Bochum, Germany. E-mail address: sebastian.ocklenburg@rub.de (S. Ocklenburg). Brain and Cognition 109 (2016) 34–39 Contents lists available at ScienceDirect Brain and Cognition journal homepage: www.elsevier.com/locate/b&c