Previous experimental studies indicate that gaze-following is a reliable indicator of advanced cognitive capacity in social primates. Group-living primates, in particular, must navigate complex social relationships among group members and other conspecifics, and individuals thus require higher-level social-cognitive skills. The purpose of this research was to evaluate species-specific variation in the cognitive abilities of a unique population of semi-free-ranging apes composed of 15 orangutans and 30 chimpanzees housed at the Center for Great Apes in Wauchula, Florida, assess the degree to which individuals in these populations visually communicate with conspecifics via gaze-following, as well as investigate their capacity for joint visual attention. This research involved three separate observational studies, the goals of which were: to determine the capacity of subjects to follow the gaze of a human social partner; to assess individual frequencies of social monitoring as a function of age, sex, and species; and to investigate the ability of subjects to engage in joint attention with a human social partner toward functional objects (i.e. manipulative toys/possible tools) versus non-functional objects. Results of ANOVA and t-tests provided strong evidence for all three abilities and demonstrated that variation in frequencies of these behaviors between and within species was a consequence of the effects of sex and age. The significance of this research resides in the new insights that may be gained into the phylogenetic cognitive substrates underpinning the evolution of cognition and visual communication in the human lineage via our closest relatives, the great apes.