Is laterality adaptive? Pitfalls in disentangling the laterality–performance relationship

Abstract

Unlike non-human animal studies that have progressively demonstrated the advantages of being asymmetrical at an individual, group and population level, human studies show a quite inconsistent picture. Specifically, it is hardly clear if and how the strength of lateralization that an individual is equipped with relates to their cognitive performance. While some of these inconsistencies can be attributed to procedural and conceptual differences, the issue is aggravated by the fact that the intrinsic mathematical interdependence of the measures of laterality and performance produces spurious correlations that can be mistaken for evidence of an adaptive advantage of asymmetry. Leask and Crow [Leask, S. J., & Crow, T. J. (1997), How far does the brain lateralize?: an unbiased method for determining the optimum degree of hemispheric specialization. Neuropsychologia, 35(10), 1381-1387] devised a method of overcoming this problem that has been subsequently used in several large-sample studies investigating the asymmetry-performance relationship. In our paper we show that the original Leask and Crow method and its later variants fall victim to inherent nonlinear dependencies and produce artifacts. By applying the Leask and Crow method to random data and with mathematical analysis, we demonstrate that what has been believed to describe the true asymmetry-performance relation in fact only reflects the idiosyncrasies of the method itself. We think that the approach taken by Leask in his later paper [Leask, S. (2003), Principal curve analysis avoids assumptions of dependence between measures of hand skill.

Handedness Development: A Model for Investigating the Development of Hemispheric Specialization and Interhemispheric Coordination

“…Indeed, many critical reviews of HS/HC note problems of inadequate statistical power, missing details on proportion of those showing atypical lateralization, and the use of many different, often insufficiently validated, methods to ascertain functional lateralization [3,39,40]. Thus, there are too many instances of failures of replication [41], poor research designs [42], and the accumulation of conflicting evidence that fails to support any explanation of the character of HS/HC (e.g., [43,44]) or for the mechanisms responsible for the specialization [45].…”

Progressive Voxel‐Wise Homotopic Connectivity from childhood to adulthood: Age‐related functional asymmetry in resting‐state functional magnetic resonance imaging

“…More recently, functional asymmetry has been appraised through multiple neuroimaging modalities in the human brain, and persuading evidence has been offered for the notion of an overall trend in hemispheric specialization for emotional processing (Fusar-Poli et al, 2009) and language tasks (Riès et al, 2016), although significant interindividual differences seem to be described. Further evidence corroborated functional asymmetry in the brain at the molecular and cellular level (Kantonen et al, 2020;Toga & Thompson, 2003), yet a high degree of hemispheric specialization is not always advantageous at the individual, group, or population level (Paszulewicz et al, 2020). On the contrary, a high degree of hemispheric specialization has been observed as a predisposing factor for greater risks of performance deficits subsequent to structural lesions (Knecht et al, 2002).…”