Do your actions help me remember better? Effects of pointing movements performed by self and others on visuo-spatial working memory: evidence from behavioral, eye-tracking and event-related potential data

The current dissertation investigates how pointing movements performed towards to-be- remembered target locations together with a task-partner influence visuo-spatial working memory (VSWM). Previous studies have shown that, under specific conditions, spatial arrays that have been pointed to during encoding are better recognized than passively viewed ones. The first experiment described here was aimed at replicating these results. Participants were presented with two spatial arrays, one of which was encoded through mere visual observation (the no-move array), while the other was encoded through observation accompanied by pointing movements towards target locations (the move array). The encoding was followed by a recognition test in which participants had to decide whether a probe array was equal or different from one of the arrays presented during the study phase. Results replicated the memory advantage of pointed-to arrays as compared to merely observed ones. Since a number of studies suggest that perceiving an action and executing it are functionally equivalent and activate common representational structures, we proceeded to investigate whether pointing movements performed by a task-partner could have similar effects. No memory advantage was found when participants passively observed the pointing movements performed by the task-partner. A joint condition of the task was thus tested where the participant and the task-partner took turns in performing the pointing movements towards the target locations in the move array (recognition was always performed by the participants). Results showed that in this joint-action condition the pointing movements performed by the task-partner benefited individual’s visuo-spatial working memory to the same extent as self-performed pointing movements. Further experiments were conducted to investigate the processes underlying the encoding of no-move and move arrays, either jointly pointed by the participant and the task-partner or pointed only by the task-partner. In two eye-tracking experiments, the eye movement patterns for the two types of arrays were recorded. The analysis of eye movements yielded results that are in line with the behavioral findings and showed that fixations to move arrays were higher in number and longer in duration than the fixations to no-move arrays but only when the participant and the task-partner alternate in making the pointing movements. No difference in eye movement patterns was found for the move and no-move arrays when the participant merely observed pointing movements performed by the task-partner. We propose that, in the joint-action condition, self and others’ actions are coded at the same representational level and their functional equivalency is reflected in a similar pattern of eye fixations. Behavioral experiments investigating the effects of a number of other factors on visuo-spatial working memory are also reported, including the partner’s involvement in the task or the animacy of the task-partner. Findings show that: a) in the joint-action condition, the infrequent execution of pointing movements by the participants (about 16%) is sufficient to successfully produce a social context which leads to the co-representation of partner’s actions; and b) a memory advantage occurs when the turn-taking task-partner is replaced by a moving cartoon hand, but only in the joint-action condition (there is no advantage when the movements were only carried out by the cartoon hand). The latter finding indicates that the mere presence of the cartoon hand is not sufficient to trigger the memory advantage. Altogether, the results suggest that the social context between the participant and the task-partner modulates the task co-representation process. Finally, event related potential (ERP) data were recorded in order to investigate the encoding processes involved in processing self and other’s pointing movements in the joint-action condition. In summary, the current dissertation investigates, from behavioral and physiological points of view, the question of how performing an action together with a partner influences individual’s encoding processes and suggests future directions for research investigating the influence of jointly performed tasks on individual’s memory.