Natural syntax rules control action sequence of rats

Knowledge of the principles by which behavioral sequences are generated is essential to progress in our understanding of neural mechanisms. We describe here a set of natural principles or syntax rules that organize the components of grooming and feeding. The behavioral stream of facial grooming or of taste-elicited ingestive/aversive consummatory actions of rats can be viewed as a long series of individual movements linked together to form functional sequences. In order to ascertain the syntax rules that determine how these actions are linked together, many thousands of spontaneous grooming and elicited ingestive/aversive actions were videotaped and scored with a microcomputer. Techniques of information analysis of sequential stereotypy, tabulation of the sequential transitions between single actions and between action groups, and visual inspection for linear action chains, were employed to expose underlying rules of behavioral sequencing. These analyses revealed two global patterns: action perserveration and transitional reciprocation between sequential pairs and triplets, which together account for approximately 75% of all sequential transitions during grooming and ingestion/aversion. The pattern of transitional reciprocation could be divided further into patterns of alternation between individual actions on the one hand, and between perseverating bouts of actions on the other. Global syntax rules applied equally to actions emitted during grooming or during taste-elicited ingestion/aversion. In addition, a specific rule of linear chaining was found to apply only to facial grooming. These natural rules of action syntax provide insight into the sequential structure of behavior, and lend themselves well to analyses of neural mechanisms.