Genetic vs. environmental contributions to human handedness: Insights gained from studying individuals with unilateral hand injuries

Abstract

Four hundred eleven individuals who had suffered temporary unilateral hand injuries were assessed on five hand preference behaviors after their recovery. Measures of shifts to contralateral hand use experienced during and after the recovery period were taken. The best predictor of hand use shifts during the injury recovery period was whether the injury was to the preferred or nonpreferred hand. The incidence of postinjury contralateral shifts was low but was greater than that observed over a simulated injury period in a control group of 384 individuals who had not experienced a hand injury.

Writing with the non-dominant hand: Cross-handedness trainability in adult individuals

“…Contrary to what would be expected due to the decrease in fine motor control with age (Smith et al, 1999), the later life group did not show a significantly lower amount of improvement in legibility. Studies using MRI scans have shown that older individuals tend to recruit more cortical areas during learning than younger individuals, thereby compensating for any possible loss in fine motor control (Johansson, 2004).…”

“…In learning new simple tasks, such as finger tapping, the non-preferred hand will improve its performance with training, but it will not reach or exceed the level of skill of the preferred hand. Other studies (Chapman & Henneberg, 1999;Galobardes, Berbstein, & Morabia, 1999;Porac, 1995), found that it is possible for the non-preferred hand to be trained to write as legibly as with the preferred one. This was further strengthened by Teixeria and Paroli (2000), who found no difference in simple motor task control, strength, or positioning between the preferred and non-preferred hand and arm.…”

“…In a study of three participants, Lindemann and Wright (1998) suggested that the high-quality writing with the non-preferred hand seen after minimal practice showed that learning of this handwriting occurs at the muscle recruitment level and not at the cortical level. Because plasticity and fine motor control of the hand decrease with age (Smith et al, 1999), it would be possible to test this suggestion by observing the amount of improvement in non-preferred hand performance with age.…”

Illness and accidental injury in young and older adult left‐ and right‐handers: Implications for genetic theories of hand preference

“…However, this type of genetic-environment interaction analysis is useful in attempting to account for the manifest complexities of human handedness types. Porac (1995aPorac ( , 1995b argued that life experience factors must be taken into account by genetic theories because these influences are meaningful forces in the formation of hand preference side and strength. It is also possible that genetic determination of human hand preference is more complex than that conceptualized in several of the most prominent contemporary models (Annett, 1985;Coren, 1994Coren, ,1995bMcManus, 1985).…”

Handedness and Asymmetry of Motor Skill Learning in Right-handers

“…Genetic and familial influences, as well as social and cultural factors,20 have been considered to underlie handedness. Better skill performance in one hand can be seen as a training effect from more frequent use of one hand.…”