Specific aspects of our personalities may be influenced directly by events that occurred in our childhoods, according to study conducted in rats described in an article released on July 29, 2008 in the open-access journal PLoS ONE.

Using a rat model, scientists at the University of New Mexico Psychology Department and Rockefeller University examined how early life experiences can influence the social skills and abilities in stressful situations. In this study, a group of young rats was removed from the home environment during infancy in the first three weeks of life and thus exposed to novel inputs during infancy. The cumulative time spent outside the home environment was approximately 60 minutes.

Subsequently, when observed in adult life at 24 months of age, they were set to compete against one another for a chocolate reward. Mice who were exposed to novelty as infants were able to beat competitors more often than their unexposed siblings. Furthermore, across repeated sessions, the novelty-exposed rats had lower levels of stress hormones released into the bloodstream, a finding which suggest that they adapted faster to the stressful situation. These findings indicate that even very brief exposures to a new environment in infancy can impact social competitive ability and the stress response throughout life.

Following this, the researchers investigated whether the siblings had different adult traits depending on the care received from their mothers in infancy. To do this, they measured how much the mother rats licked and groomed each pup after a novelty exposure procedure, and how consistent this care was. The mother rats that delivered more total care to their pups were generally less consistent in giving care between different days. Novelty-exposed rats had better adaptive stress responses if their mothers gave consistent but lower total levels of care.

The implications that this research has on the understanding of human personalities can be difficult, but according to the researchers, it does indicate the pattern and consistency of maternal care may have a strong influence on a child’s development. This is contrast to some previous beliefs that the overall amount of care from the mother is the important factor.

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About the University of New Mexico

The University of New Mexico is the state’s largest university, serving more than 32,000 students. UNM is home to the state’s only schools of law, medicine, pharmacy and architecture and operates New Mexico’s only academic health center. UNM is noted for comprehensive undergraduate programs and research that benefits the state and the nation.

Social Competitiveness and Plasticity of Neuroendocrine Function in Old Age: Influence of Neonatal Novelty Exposure and Maternal Care Reliability.
Akers KG, Yang Z, DelVecchio DP, Reeb BC, Romeo RD, et al.
PLoS ONE 3(7): e2840.
doi:10.1371/journal.pone.0002840
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Written by Anna Sophia McKenney