When the social behavior of non human primates is used as a model for understanding human normal and abnormal aggressive behavior, contextual analyses are necessary because the meaning of any interaction does not depend only upon its intrinsic characteristics and upon those of the actor and the receiver, but also upon the social context in which it happens. Using social behavior sequences, a procedure to evaluate the social context is presented, so any behavior can be studied in relation to the preceding and following ones.

Four captive groups of vervet monkeys (Cercopithecus aethiops) with different number/age/sex composition were used (n=29). The groups were housed in outdoor enclosures and had food and water available ad libitum. By means of direct observation, all individual and social behaviors were captured in an audio tape recorder, maintaining their actual order of occurrence. The actor and receiver were also noted. Each behavior and each animal had a code number previously assigned so at the end of each one-hour session a list of three digits was available (behavior, actor and receiver). The data obtained with this sequential procedure was transcribed to diskettes and analyzed with several Visual Basic programs designed ad hoc. Thirty behavior patterns were considered and grouped into 6 categories, each one assigned with a different color: Affiliation-white; Play-yellow; Sex-green; Agonism-purple; Emotional Tension Indicators-brown and Aggression-red. Since alcohol is a social facilitator, the modifications induced by spontaneous alcohol intake were used to prove the procedure. Each group was recorded daily during two sessions: The control one and that during which all subjects had free access to a sugar-sweetened water preparation containing 15% w/v of commercial rum (45^o G.L.). The results include 52 control and 52 alcohol sessions.

Each behavior sequence was plotted with a succession of squares, colored according to the behavior category they stood for. The resulting image produced immediate notion of the social context generated by the group and the effects of alcohol are evident at a glance. Further analysis was accomplished by braking each sequence into Behavior Codons (BCs): starting the analysis at the first behavior of each sequence (b1), the first BC was formed with b1, b2 and b3. Moving the pointer one step at a time all the BCs were obtained until the end of the sequence was reached. Similar BCs were added for all control and experimental sessions for each group separately. Spearman’s test showed high correlation coefficients among all groups (r > 0.9; p < 0.001).

Results obtained with traditional procedures showed statistical significance in the increase of Affiliation, Play and Aggression (p > 0.001), during alcohol sessions. However, BC analysis evidenced different social mechanisms involved in both experimental situations. The BC Affiliation-Affiliation-Affiliation (the most common in control sessions) was broken in the alcohol sessions and appeared in units or pairs within the BC. Conversely Play and Aggression, observed in units or pairs within the BCs of control sessions, during the alcohol sessions the triplets Play-Play-Play and Aggression-Aggression-Aggression increased, while pairs and units within the BCs decreased. BC analyses show the compulsive aspect observed in play, and suggest escalated aggression as well as an increase in the probability of violent behavior induced by alcohol.