title: Adverse birth factors predict cognitive ability, but not hand preference.
abstract: OBJECTIVE
  There is a persistent theory that birth stress and subsequent brain pathology play an important role in the manifestation of left-handedness. Evidence for this theory, however, is mixed and studies are often beset with problems related to small sample sizes and unreliable health reports.
  
  
  METHODS
  TO avoid these issues, this study used a sample of approximately 10,000 children from the British Cohort Study. The study contains objective birth-health reports and comprehensive measures of socioeconomic status, handedness, cognitive ability, and behavioral/health issues.
  
  
  RESULTS
  Regression analyses showed that variables associated with birth stress affected cognitive/behavioral/health outcomes of the child. Despite this, these same factors did not affect the direction or degree of hand preference.
  
  
  CONCLUSIONS
  We have therefore demonstrated a dissociation whereby adverse birth factors affect the brain's cognitive ability, but not handedness, and by implication, cerebral lateralization. The study also demonstrated a link between left-handedness and reduced levels of cognitive ability. This link cannot be due a generalized birth-stress mechanism and may be caused by specific mechanisms related to changes in cerebral dominance.
authors: School of Psychology, Flinders University, Adelaide, Australia. mike.nicholls@flinders.edu.au
authors: Michael E R
authors: ME
authors: Nicholls
authors: David W
authors: DW
authors: Johnston
authors: Michael A
authors: MA
authors: Shields
mesh_terms: D002648:Child; D002653:Child Behavior Disorders / Q000453:epidemiology / Q000523:psychology; D003071:Cognition / Q000502:physiology*; D015331:Cohort Studies; D002658:Developmental Disabilities / Q000453:epidemiology / Q000523:psychology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006304:Health Status; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009483:Neuropsychological Tests; D016017:Odds Ratio; D036801:Parturition / Q000502:physiology*; D011237:Predictive Value of Tests; D011597:Psychomotor Performance / Q000502:physiology; D012044:Regression Analysis; D012307:Risk Factors; D012737:Sex Factors; D012959:Socioeconomic Factors; D013312:Stress, Physiological; D006113:United Kingdom / Q000453:epidemiology; D014825:Vocabulary