Attentional orienting and biological motion: A behavioral and eye-tracking investigation.

The current thesis aims to understand how the processing of biological motion influences human attentional systems. Past investigations on the interaction between socially significant stimuli and attentional mechanisms have mostly focused on face processing. Results indicated that faces can both facilitate attention and optimize visual search by suppressing attention to return to an already explored location. The latter phenomenon is known as Inhibition of Return (IOR) and it is a fingerprint of exogenous attentional orienting that allows for the detection of sudden and salient stimuli. To the best of our knowledge there is no previous investigation on the IOR with biological motion. This thesis project contributes at filling this gap. To this end, the first part of the thesis theoretically approaches how biological motion processing can be supported by exogenous attentional brain mechanisms. The second part of the thesis concerns the empirical investigation of the phenomena. Specifically, a behavioral study aiming at exploring both facilitatory and inhibiting attentional effects of biological motion will be presented. The study implements biological motion as a centrally non-predictive cue in a classic visuo-spatial orienting Posner task. Importantly, since attention is closely linked to the motor system and especially saccadic allocation (premotor theory of attention) two different effector systems are being studied, manual responses and eye movements. This manipulation will allow us to explore whether biological motion can elicit both facilitation and inhibition of return, and if this is mediated by effector-specificity. The dependent variables are reaction time speed and accuracy, as well as saccadic latencies. The independent variables are the stimulus-onset asynchrony between the presentation of cue and target and the validity of the biological motion with the target. The results of this thesis will shade light into how humans process and pay attention to socially-significant stimuli.