Broadening the scope: Increasing phenotype diversity in laterality research

A deep phenotyping approach to assess the association of handedness, early life factors and mental health

“…Functional asymmetries are widespread across species 1 , 2 and can be found in simple motor tasks 2 , complex socio-behavioral patterns 3 , 4 , and in cognitive information processing 5 , 6 . For humans, the most obvious form of lateralization is handedness.…”

“…One severe limitation that does apply to the majority of cited studies is the issue of shallow phenotyping. As we outlined in more depth in a recent opinion paper 3 , shallow phenotyping can be understood as a waiver to conceptualize (dimension of conceptualization) and to measure (dimension of measurement) a phenotype with sufficient complexity. Regarding the dimension of conceptualization in the case of functional asymmetries, it becomes apparent that most studies only assess handedness but largely neglect other forms of functional lateralization.…”

“…However, other kinds of functional asymmetries may be better suited than handedness for some research interests. For instance, we endorsed the integration of social laterality phenotypes such as hugging since these allow to capture different evolutionary pressures and may be better suited for research across species 3 . From a dimension of measurement, it may be claimed that handedness, the most common proxy for hemispheric asymmetries, is commonly not assessed accurately.…”

Environmental and genetic determinants of sensorimotor asymmetries in mother-infant interaction

“…These findings are consistent with the hypothesis that atypical cerebral and/or behavioral lateralization might reflect a potentially dysfunctional brain organization, maybe due to a non-optimal distribution across the two hemispheres of specific functions. In fact, although the scientific debate on typical brain lateralization is still ongoing, the prototypical brain template of lateralized functions posits the left hemisphere as more dominant for limb motor control, language and calculation, and the right hemisphere as more dominant for spatial abilities and emotion recognition from faces and speech (see Vingerhoets, 2019;Forrester et al, 2020;Pfeifer et al, 2022).…”

“…These findings are consistent with the hypothesis that atypical cerebral and/or behavioral lateralization might reflect a potentially dysfunctional brain organization, maybe due to a non-optimal distribution across the two hemispheres of specific functions. In fact, although the scientific debate on typical brain lateralization is still ongoing, the prototypical brain template of lateralized functions posits the left hemisphere as more dominant for limb motor control, language and calculation, and the right hemisphere as more dominant for spatial abilities and emotion recognition from faces and speech (see Vingerhoets, 2019 ; Forrester et al, 2020 ; Pfeifer et al, 2022 ). Given that left-handers (and also mixed-handers; Corballis et al, 2008 ) often show a hemispheric shift from left to right for language dominance and limb motor control, according to the “cognitive crowding hypothesis,” the disadvantages exhibited by individuals showing atypically-lateralized (but not necessarily reversed) templates might be due to the fierce competition in which such functions are permanently engaged with the other cognitive functions typically located in the other hemisphere (McManus, 2002 ; Lidzba et al, 2006 ; Nicholls et al, 2010 ; Papadatou-Pastou and Tomprou, 2015 ).…”