J Psychol Cognition 2016; 1 (1): 40-56 J Psychol Cognition 2016 Volume 1 Issue 1 40 Journal of Psychology and Cognition Effects of the number of objects and locations on attentional allocation and processing in a visual short-term memory task. Aymen Ben Abbes 1 , Yousri Marzouki 2,3 , Thierry Ripoll 2 1 University of Tunis El Manar (Institut Supérieur des Sciences Humaines de Tunis), Tunisia. 2 Aix-Marseille Université (Laboratoire de Psychologie Cognitive, CNRS) Marseille, France. 3 Qatar University, Doha, Qatar. Introduction Our visual system is continuously fooded by a huge amount of information, which constantly challenges the way we allocate our attention over space when we simultaneously select and process the most relevant "items". The most popular description in literature of the attentional allocation is the “spotlight” metaphor, which suggests that attention can operate as a beam toward a circumscribed location in order to enhance information processing at this particular position [1,2]. It has been assumed that performance can be signifcantly damaged when the visual system has to attend to many locations simultaneously due to the cost induced by distributing attention over different locations [3,4]. However, a growing substantial body of data suggests that spatial attention deployment allows the participants to pay attention to non-contiguous locations or objects while they inhibit irrelevant positions or objects interposed between them [5-8]. For example, Awh and Pashler used a partial report technique in which observers had to systematically report the identity of two targets presented at separate locations within a 5-by-5 stimulus matrix [5]. There was a valid condition in which two targets appeared at previously cued locations. In the invalid condition, one of the two targets appeared directly between the cued locations (the medial position). The authors found a strong capacity to attend to the cued locations without selecting the intervening ones. Whatever the conclusions made by these investigations, their main aim was to test the capacity to select targets among distractors and to process these targets simultaneously (detection, identifcation, memorization, etc.). Accordingly, the performance was contingent upon two sequential diffculties: frstly, the participants had to attend to the critical locations of targets to extract them from distractors, and secondly, they had to encode the properties of targets to enable their full representation. However, even if these two distinctive diffculties had been underlined in some studies [9-11], there was no systematic dissociation between them in the above-mentioned research. Xu and Chun provided an interesting framework addressing this issue called the neural object-fle theory. The latter highlighted the presence of two stages of processing: the object individuation and the object identifcation. In the Using a partial report procedure, we tried to dissociate the effect of increasing the number of attended locations from that of increasing the number of objects (digits) appearing in these locations. Participants had to allocate their attention to different locations among a set of distractors (letters). After a delay of 500 ms they had to process either one, two, three or four digits appearing at one, two, three or four previewed locations. We found that the capacity of attentional allocation over locations decreased at three attended locations and also after the increase in the number of objects while attending to four locations. The same procedure was used in Experiment 2, except that digits were used as distractors to eliminate the possible attentional re-allocation bias towards targets during the processing phase. We introduced in Experiment 3 a color contrast between targets and distractors in order to facilitate their discrimination and to reduce the spatial confguration effect of locations. The results are in line with Experiment 1 fndings and showed that the processing of multiple objects is constrained by two interacting diffculties. The frst relies on resources distribution over the attended locations whereas the second relies on parallel encoding of objects. Abstract Keywords: Attentional allocation, Division of attention, Capacity threshold. Accepted October 07, 2016