Jean-Baptiste Leca, Ph.D.
Direct social influence in the acquisition of stone handling behavior
During their first three months of life, infants spent on average 75% of the time within one-meter of their mother, significantly more than they spent with other group members.
This high level of proximity to the mother had a significant impact on the age at which stone handling was acquired. Infants of mothers with higher stone handling frequencies first displayed the behavior earlier than infants of less frequent stone handling mothers, and even earlier than infants of mothers that were observed handling stones.
Moreover, infants of frequent stone handling mothers spent twice as much time (83%) watching their mothers when she was handling stones than did infants whose mothers showed low stone handling frequency (42%).
The former tried to take stones away from their mothers in 75% of the stone handling bouts whereas the latter tried to do so in only 33% of these bouts.
These results suggest that the acquisition of stone handling in infants was strongly influenced by the relative amount of time spent in proximity to their mothers as stone handling models, as well as the frequency of the behavior displayed by such demonstrators (Nahallage & Huffman, 2007).