Abstract

In this thesis I investigated whether and to what extent performing a task with another person may change individual cognitive performance. Interference paradigms are particularly suitable for addressing this issue. The rationale behind the use of these paradigms is that most of them can be split in two complementary or independent tasks assigned to two different individuals. By comparing task performance when participants act in the joint context and when they perform the task individually, important information may be derived about whether the co-actor’s task is represented and how this representation influences one’s own performance. Following this approach, I adopted the joint version of two different and well-known paradigms: the picture-word interference paradigm (Study 1: Experiments 1, 2, 3) and the Simon task (Study 2: Experiments 4, 5, 6). Both paradigms allow understanding how people can deal with the task irrelevant information when the accomplishment of the task is achieved in a joint (and cooperative) context. The results of both studies provided converging evidence showing that, regardless of the paradigm used, task sharing determines the disappearance of the interference effect produced by the task irrelevant information (Study 1) or by the (incidental) spatial representation of an alternative response (Study 2). The disappearance of the interference effects, however, occurred only when the co-actor was thought to work on different or complementary stimuli but not when s/he was in charge of the same stimuli as the participant. These findings will be accounted for by taking into consideration both the specific peculiarities of each paradigm exploited and the strategic processes of division of labor that can be established between two co-acting individuals.