Social competence of adult chimpanzees (Pan troglodytes) with severe deprivation history: I. An individual approach.

Early social deprivation in highly social mammals interferes with their varying needs for security and stimulation. Toleration of social stimulation was studied in 18 adult ex-laboratory chimpanzees, who had been deprived for 16 to 27 years, during their 1st year after resocialization into 1 of 3 social groups. For this, a model of social competence was developed with 5 grades of social stimulation. The chimpanzees were classified as either early deprived (EDs; M = 1.2 years) or late deprived (LDs; M = 3.6 years) according to their age at entering the laboratory. EDs did not differ significantly from LD chimpanzees in the first 3 grades of social stimulation (i.e., the toleration of stationary vicinity, initiation of brief sociopositive contacts and gentle social play). LDs, however, clearly exceeded EDs in the 4th and 5th grade of social stimulation (i.e., their engagement in allogrooming and their toleration of passive close proximity). Furthermore, LDs showed greater social initiative in changing a social situation and had more expanded grooming networks compared with EDs. Moreover, in LDs and ED females, but not in ED males, toleration of stationary vicinity increased from the 1st to the 2nd year of group living.