Is There Any Difference Between the Spatial Response Code Elicited by Bilateral Symmetrical Biological and Non-Biological Stimuli?

Is There Any Difference Between the Spatial Response Code Elicited by Bilateral Symmetrical Biological and Non-biological Stimuli? Paola Ricciardelli (paola.ricciardelli@unitn.it) Dept. of Cognitive Sciences and Education, University of Trento, Via Matteo del Ben, 5 38068 Rovereto (TN), Italy Claudia Bonfiglioli (bonfiglioli@form.unitn.it) Dept. of Cognitive Sciences and Education, University of Trento, Via Matteo del Ben, 5 38068 Rovereto (TN), Italy Cristina Iani (iani.cristina@unimore.it) Dept. of Social, Cognitive and Quantitative Sciences, University of Modena and Reggio Emilia, via Giglioli Valle, 9 42100 Reggio Emilia, Italy Sandro Rubichi (rubichi@unimo.it) Dept. of Social, Cognitive and Quantitative Sciences, University of Modena and Reggio Emilia, via Giglioli Valle, 9 42100 Reggio Emilia, Italy Roberto Nicoletti (nicoletti@dsc.unibo.it) Dept. of Communication Disciplines, University of Bologna, via Azzo Gardino, 23 40122 Bologna, Italy Abstract The aim of the present study was to investigate whether the biological relevance of the stimulus could enhance task- irrelevant spatial information delivered by a pair of bilateral stimuli. Participants had to perform a Simon-like task in which they were required to respond to the color of two framed squares (on and off-centered), two framed arrows, or two schematic eyes by pressing one of two keys on the left and on the right of the body midline. Results showed that regardless of stimulus type responses towards the direction indicated by the stimuli (corresponding stimulus-response pairings) were faster than responses against it (non-corresponding stimulus-response pairings). It is argued that the biological relevance of the stimuli does not seem to play a crucial role in the automatic processing of stimulus inherent spatial properties. Introduction Spatial directional stimuli have been shown to influence our performance in a variety of tasks. In daily life, for example, arrows are commonly used by humans to convey spatial information and have acquired a symbolic and directional meaning. Indeed, central arrows have been also employed as cues to study the voluntarily orienting of visual-spatial attention (e.g., Posner, 1980), suggesting that their spatial and directional meaning can influences people’s attentional behavior. Moreover, there is evidence that spatial information is processed automatically and cannot be ignored even in many situations for which it is irrelevant to the task to be performed (e.g., Tsal L see Hommel & Prinz, 1997; Lu & Proctor 1995, for reviews). In a typical Simon task stimuli appear in one of two right-left locations and participants respond with right or left effectors. Even if stimulus location is task-irrelevant, when stimulus and response positions are on the same side (e.g., right-right or left-left; i.e. corresponding pairings) performance is faster and more accurate than when they are on opposite sides (e.g., stimulus on the right side and response on the left side, or vice versa; i.e. non-corresponding pairings). Thus, in the Simon task, the irrelevant spatial information is processed, even though participants are clearly instructed to select the response exclusively on the basis of the relevant, non-spatial stimulus dimension. Recent works have demonstrated that also symbolic centrally presented stimuli such as an arrow can produce the Simon effect (e.g., Masaki, Takasawa, & Yamazaki, 2000; Proctor, Marble, & Vu, 2000). Intriguingly, Simon effects have also been reported for gaze direction (Zorzi, Mapelli, Rusconi, & Umilta, 2003 ; Ansorge, 2003b). Therefore, it seems that also spatial information intrinsic to many different categories of visual objects (e.g., central arrows and gaze) is automatically coded and affects performance. An interesting question is whether different stimulus types convey different amounts of spatial information. For instance, it may be the case that the spatial salience of certain stimuli and objects is more pronounced by virtue of the symbolic or biological meaning they convey, and thus exert a greater influence on performance. Gaze direction can be one of these stimuli given its biological and social value. Indeed, eye gaze