Processing regularities without language

Natural environments contain different regularities: from the daylight/darkness cycle to the use of alarm calls to signal the presence of predators. Different species can hence find advantage of extracting regularities to adapt their behaviour to the physical and social environment. In this thesis I investigate the capabilities of different species to process visual and acoustic regularities. The experiments presented here are structured around the distinction between different types of regularities that can work as predictors †" repetitions of the same event, item-based regularities, and abstract regularities †" and correspondent computational capabilities. As a general working hypothesis, I have investigated whether the processing of abstract regularities requires the capability to extract item-based regularities and whether the processing of item-based regularities requires the capability to extract repetitions of the same events, in a hierarchical organization. Another line of research concerns the processing of positional regularities. These patterns refer to the specific locations of the stimuli, for instance the edges of a string, or the relative position of the tokens that compose a string. In the first study I used a new paradigm in which subjects, cotton-top tamarins, faced the problem of avoid auditory masking in the production of contact calls during intermittent background noise. In order to vocalize during silent intervals, tamarins could use information conveyed by repeated stimuli that functioned as valuable predictors of silent intervals. The results show that all subjects mastered the repetition of simple acoustical cues: tamarins extracted predictive acoustic cues from an intermittently noisy environment and used this information to time vocal output and avoid masking. Using visual configurations, I also studied the computational capabilities of these monkeys to process item-based and abstract regularities in the visual domain. Tamarins were first trained to discriminate between patterns consistent and inconsistent with either an item-base regularity †" A(X)^n B †" or an abstract regularity †" Ai(X^nAi. In the subsequent test phase, they had to distinguish between new stimuli consistent or inconsistent with the target rule. The results are consistent with a hierarchical organization of computational capabilities: while tamarins promptly mastered the item-based pattern, they were able to generalize only partially to new stimuli consistent with the abstract regularity. Hence, although this thesis does not completely answer the empirical question about the hierarchical organization of regularity processing, it brings relevant data to the debate. The second line of research investigates regularity processing using using the interspecific comparison. Using the habituation-discrimination method with chimpanzees and an analogous method with human beings, I compared the strategies used in these species to encode positional information in acoustic sequences. Results suggest that both chimpanzees and humans, irrespective of the possession of language, have a bias in favour of the elements located at the edges of acoustical strings. In choosing the methods to study cotton-top tamarins, chimpanzees, and human beings, I have used different paradigms and modalities of presentation of the stimuli that take into consideration species-specificities (constraints and specializations). I have also paid close attention in designing experiments that can be used to study either positional regularities, repetitions of the same stimuli, item-based, and abstract regularities, while leaving the possibility to extend the study of the hierarchical organization of computational capabilities open.