Social cognition, joint attention, and communicative competence from 9 to 15 months of age.

At around 1 year of age, human infants display a number of new behaviors that seem to indicate a newly emerging understanding of other persons as intentional beings whose attention to outside objects may be shared, followed into, and directed in various ways. These behaviors have mostly been studied separately. In the current study, we investigated the most important of these behaviors together as they emerged in a single group of 24 infants between 9 and 15 months of age. At each of seven monthly visits, we measured joint attentional engagement, gaze and point following, imitation of two different kinds of actions on objects, imperative and declarative gestures, and comprehension and production of language. We also measured several nonsocial-cognitive skills as a point of comparison. We report two studies. The focus of the first study was the initial emergence of infants' social-cognitive skills and how these skills are related to one another developmentally. We found a reliable pattern of emergence: Infants progressed from sharing to following to directing others' attention and behavior. The nonsocial skills did not emerge predictably in this developmental sequence. Furthermore, correlational analyses showed that the ages of emergence of all pairs of the social-cognitive skills or their components were inter-related. The focus of the second study was the social interaction of infants and their mothers, especially with regard to their skills of joint attentional engagement (including mothers' use of language to follow into or direct infants' attention) and how these skills related to infants' early communicative competence. Our measures of communicative competence included not only language production, as in previous studies, but also language comprehension and gesture production. It was found that two measures--the amount of time infants spent in joint engagement with their mothers and the degree to which mothers used language that followed into their infant's focus of attention--predicted infants' earliest skills of gestural and linguistic communication. Results of the two studies are discussed in terms of their implications for theories of social-cognitive development, for theories of language development, and for theories of the process by means of which human children become fully participating members of the cultural activities and processes into which they are born.

Processes of social learning in the tool use of chimpanzees (Pan troglodytes) and human children (Homo sapiens).

Common chimpanzees (Pan troglodytes) and 2-year-old human children (Homo sapiens) were presented with a rakelike tool and a desirable but out-of-reach object. One group of subjects observed a human demonstrator use the tool in one way, and another group observed a demonstrator use the tool in another way. Children in both cases did what the model did. Chimpanzee subjects, however, behaved identically in the 2 model conditions. Both groups performed better than subjects who saw no demonstration. This pattern of results suggest that the chimpanzees were paying attention to the general functional relations in the task and to the results obtained by the demonstrator but not to the actual methods of tool use demonstrated. Human children were focused on the demonstrator's actual methods of tool use (her behavior). The different social learning processes used by the 2 species have implications for their different forms of social organization.

Antide (Nal-Lys GnRH antagonist) suppression of pituitary-testicular function and sexual behavior in group-living rhesus monkeys.

The ability of a Nal-Lys gonadotropin releasing-hormone antagonist (Antide) to suppress pituitary-testicular function and male sexual behavior was studied in seven group-living adult male rhesus monkeys. Each male received a single 15 mg/kg b.wt. subcutaneous injection of Antide dissolved in equal volumes of propylene glycol and sterile water. Prior to Antide treatment, and at two, four, and eight weeks after Antide, males received an IV bolus of GnRH (50 ng/kg) to assess pituitary and testicular function. For four weeks before and eight weeks after Antide treatment, blood samples and behavioral observations were collected three times weekly in a 74-member heterosexual group. Antide levels increased to more than 150 ng/ml 24 h postinjection and remained above 15 ng/ml for 30 days postinjection. Circulating LH and T were significantly reduced within 24 h following Antide, and remained significantly lower than pretreatment levels in all males for 5 weeks after Antide. T levels rose above 1 ng/ml while Antide levels were still significantly elevated in four males. Both LH and T returned to pretreatment levels by seven weeks post-Antide and then showed a second significant decrease during the eighth study week. Pituitary responsiveness to exogenous GnRH was reduced by Antide and remained below pretreatment levels eight weeks after Antide treatment. Testosterone secretion in response to exogenous GnRH was significantly reduced at two and four weeks post-Antide, but was at pretreatment levels by eight weeks after Antide. Male sexual behavior declined significantly within one week after Antide treatment, almost ceased completely by four weeks after Antide, and returned to pretreatment levels by seven weeks post-Antide.(ABSTRACT TRUNCATED AT 250 WORDS)