Introduction
The large body of evidence attests that the characteristics of the speed of information processing are associated with the individual differences in high-order cognitive abilities – cognitive control and intelligence (Jensen, 2006, Sheppard & Vernon, 2008). The response time in simple and complex cognitive tasks has substantial genetic component: 29.8% and 52.1%, respectively (Beaujean, 2005, Jensen, 2006) which is also associated with intelligence and working memory characteristics (Neubauer et al., 2000, Luciano et al., 2001, 2004). The GWAS study revealed the genetic variants associated with the individual differences in the speed of information processing measures (Luciano et al., 2011). However the latest research put forward the characteristics of the intra-individual distribution of response time as better measures of the speed of information processing (Raavenzwaij et al., 2011, Schubert et al., 2015). The current pilot study aims to introduce the new evidence on the genetic and environmental aetiology of the variability in the intra-individual response time distribution in adolescence.
Sample and Methods
The sample included 55 monozygotic and 82 dizygotic pairs of adolescent Russian twins (mean age 12.9 years, SD=2.3 years, 41 male pairs, 59 female pairs, 37 opposite-sex pairs). The speed of information processing was measured using Simple Reaction Time (SRT), Choice Reaction Time (CRT) and Pattern Recognition Memory (PRM) tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB, 2006). SRT and CRT tests implement Jensen’s paradigm of measuring reaction time with one and four stimuli, respectively (Jensen, 2006). In the PRM test a participant has to recognize the patterns from the previously presented set of visual patterns. The correct response times from SRT, CRT and PRM tests were used to fit the ex-Gaussian respose time distributions for each participant. The univariate twin model was applied to estimate genetic and environmental components of mean, variability and skew of the individual response time distributions.
Results and discussion
According to the preliminary analysis, the largest part of the individual differences in the response time distribution parameters is accounted for the non-shared environmental effects (77-100%) that reflects low cross-twin similarity (under 0.395). The largest genetic effects were found for the mean response time in SRT (14%) and the skew of the response time distribution in CRT (16%). The main limitation of the current study is small number of responses for each participant (under 20 trials for each test) that restricts the reliability of the measures. The additional analyses will be performed to enhance the reliability of results. First, the univariate twin model weighted by the individual ex-Gaussian distribution log-likelihood will be applied to enhance the reliability of the univariate estimates of genetic and environmental variance. Second, the Common Pathway twin model will be fit to disentangle specific and shared components of the individual differences in the response time distribution characteristics (Schubert et al., 2016).
The research was supported by the grant 17-36-01135 from the Russian Foundation for Basic Research.
