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A retrospective study of the relationship between birth history and handedness at six years
Insights
Investigating Bakan's sinistrality hypothesis, this study found that perinatal factors like breech birth and advanced maternal age (over 38) in primiparous mothers correlate with increased left-handedness in children. A notable rise in sinistrality across generations was also observed.
Area of Science:
- Neuroscience
- Developmental Psychology
- Human Genetics
Background:
- Sinistrality, or left-handedness, has been hypothesized to result from perinatal insults.
- Understanding the etiological factors of handedness is crucial for developmental studies.
Purpose of the Study:
- To investigate Bakan's hypothesis linking perinatal insult to sinistrality.
- To examine the relationship between birth history and handedness in a cohort of six-year-old children.
Main Methods:
- A cohort of 1094 six-year-old children's handedness was assessed via questionnaire.
- Birth histories were obtained from hospital records.
- Family handedness data was collected through questionnaires.
Main Results:
- A significant secular increase in sinistrality was observed, rising from 6.2% in grandparents to 17.5% in children.
- Boys exhibited a higher prevalence of left-handedness compared to girls.
- Specific perinatal factors, namely breech delivery in boys and advanced maternal age (>38) in primiparous mothers, were associated with increased sinistrality.
Conclusions:
- The study provides evidence supporting Bakan's hypothesis by identifying specific perinatal risk factors for sinistrality.
- The observed generational increase in left-handedness warrants further investigation into environmental or genetic influences.
- Findings highlight the importance of birth complications and maternal factors in the development of handedness.
Abstract:
Bakan's hypothesis that sinistrality is caused by perinatal insult was investigated by attempting to relate the handedness of 1094 six-year-old children to many aspects of their birth history ascertained from hospital records. Handedness of the children and their families was obtained by questionnaire. A secular increase in the frequency of sinistrality was noted, from 6.2% among grandparents to 17.5% among the children. Most boys were left-handed than girls. Only two aspects of birth history predisposed to sinistrality: boys born by breech delivery and children born to primiparous mothers over 38 years old were more likely to be left-handed.