When different development rates for psychological processes such as those in spatial memory exist, they can be linked to relevant brain areas via their different developmental rates. The hippocampus and caudate nucleus have been implicated in allocentric and egocentric spatial behavior changes found in youth and old age. Variation in allocentric and egocentric behavior in squirrel monkeys due to age was examined using a quadruple T-maze and animals in three age groups: 0.3 - 4 year olds, (n = 12), 5 - 10 year olds (n=12) and 11 - 17 year olds (n = 12). Subjects were trained to go to one of three goals in the maze from one of two training release locations. When they reached criterion for consistent responding, they were given probe trials pseudorandomly interspersed with the training trials in which they were released from one of the three other locations. The 12 test sessions were divided into three phases consisting of four sessions each. A 3 (age groups) x 3 (probe sites) x 3 (phases) mixed design ANOVA with repeated measures on the second and third factors revealed only a significant effect for probe site (F(1,33) = 14.55, p < .01) sing the Geisser-Greenhouse correction for heterogeneity of variance. The pattern of responding most clearly resembled route and was stable over testing. Age was not significant although there was a trend toward random behavior in young and more route-like behavior in older animals. Intrinsic maze cues effects on responding were examined. These data were analyzed using a 3 (age groups) x 2 (training groups) x 3 (probe sites) mixed design ANOVA with repeated measures on the last factor, and again revealed only a significant probe site effect (F(1,33) = 14.55, p < .01). Thus cues intrinsic to the maze did not affect response pattern. Only 13 subjects clearly used one of the three spatial strategies: 6 route, 3 direction, and 4 place. Of the remaining 23 animals 11 were young, 5 were adult and 7 were mature. Two used a variation of place, three used a combination of strategies, four were idiosyncratic, 10 used proto-route (route-like, but not systematic enough to be route) and three were random. The use of place strategy by animals as young as 4 and as old as approximately 17 implicates hippocampal changes occurring outside this age range.

Primates are known for being highly social species, living in groups of various compositions with different social structures. The study of social or observational learning has largely focussed on investigating non-human primates' abilities to imitate, with a more recent shift towards examining the social context of social learning. This shift has presented opportunities to investigate how the social context of different species affects the diffusion of socially learnt behaviours. In this thesis, I set out to monitor the spread of different experimentally seeded and naturally occurring socially learned behaviours in brown (tufted) capuchin monkeys (Sapajus sp.) and common squirrel monkeys (Saimiri sciureus).These species were selected as they form mixed species groups in the wild, and display marked differences in their social tolerances, thus presenting the opportunity to investigate conspecific and heterospecific social learning in related but differently bonded social groups. My results show evidence of social learning from conspecifics in capuchin and squirrel monkeys, attesting to that already documented in capuchin monkeys and indicating for the first time, that common squirrel monkeys can learn socially. Additionally, I demonstrate that capuchin monkeys are influenced by squirrel monkeys when foraging for food in mixed species groups. Furthermore, although squirrel monkeys are not as socially tolerant as capuchin monkeys, individuals who were better connected within the foraging test area learned experimentally-seeded techniques of models faster and more faithfully. When performing socially contagious anointing behaviours, regardless of tufted capuchin monkeys being influenced by the amount of resources provided for them to anoint with, they still performed more socially anointing than has been previously documented in other captive species, corroborating the levels of social anointing demonstrated in semi-free ranging groups. Further support was found for anointing demonstrating a social bonding and medicinal function in tufted capuchin monkeys.