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Handedness in the human fetus
P G Hepper1, S Shahidullah, R White
1School of Psychology, Queen's University of Belfast, Northern Ireland.
Neuropsychologia
|January 1, 1991
Summary
Fetal thumb-sucking reveals pre-birth handedness, challenging previous assumptions. This study observed a consistent right-hand preference in fetuses, indicating that behavioral asymmetries like handedness begin before birth.
Area of Science:
- Developmental psychology
- Neuroscience
- Human embryology
Background:
- Behavioral asymmetries, particularly handedness, have been extensively studied.
- Previous research indicated that such asymmetries only emerge after birth.
Purpose of the Study:
- To investigate the presence of handedness in fetuses before birth.
- To determine if fetal behavior, such as thumb-sucking, indicates laterality.
Main Methods:
- Ultrasound observations were conducted on fetuses from 15 weeks gestation to term.
- Fetal thumb-sucking preferences were recorded and analyzed.
- Correlation with fetal position and newborn head position was assessed.
Main Results:
- A significant bias towards sucking the right thumb was observed in fetuses.
- This right-hand thumb-sucking preference remained consistent throughout pregnancy.
- The preference was independent of fetal position but correlated with newborn head position.
Conclusions:
- Handedness is present prior to birth, evidenced by fetal thumb-sucking.
- These findings suggest that the origins of laterality are established during prenatal development.
- Further research is needed to explore the implications for later developmental trajectories.