How faces affect object-based attention

This dissertation investigates the object-based attention (OBA) effect specifically in human faces within the framework of the double-rectangle paradigm. It consists of four studies aimed at systematically examining the OBA effect in faces and testing hypotheses that can explain the obtained results. The OBA effect is a selective attention mechanism suggesting that attention operates with objects as units. While extensive research has been conducted on the OBA effect with various objects, human faces have received relatively less attention in this context. This dissertation seeks to fill this research gap by focusing on the OBA effect in human faces. Study 1 found that the OBA effect was not present in faces when presented in the double-rectangle paradigm, in contrast to the OBA effect observed in non-face objects. Additionally, the study identified a significant impact of the horizontal bias of attention on the OBA effect. To mitigate this bias, a correction for the OBA effect was proposed. This correction aimed to eliminate the confounding influence of the horizontal bias in order to obtain more accurate results in subsequent experiments. The proposed correction method was then utilized in the following experiments to ensure a reliable and unbiased assessment of the OBA effect. Study 2 aimed at investigating the absence of the OBA effect in faces. Despite changing the race of faces and removing the eye region, no OBA effect was observed. These findings suggest that neither the global features such as race nor specific features such as the eye alone can account for the absence of the OBA effect in faces. To further explore the influence of the entire face's content, which may induce a filtering cost, an experiment was conducted where the entire face disappeared before the response was required. In this case, the OBA effect was observed in both faces and non-face objects, without any interaction, indicating that the entire face content is responsible for the absence of the OBA effect in faces. Study 3 aimed to provide further insights into the absence of the OBA effect in faces by examining attentional shifting and holistic processing. The study revealed that the OBA effect diminished and even reversed when the objects induced more holistic components. Additionally, from a fundamental perspective, the study found that there is an additional cost associated with engaging or disengaging spatial attention from faces, which ultimately leads to the absence of the OBA effect when faces are involved. Study 4 aimed to replicate the experiment conducted in Study 1 by recruiting a specific population of adults diagnosed with Autism Spectrum Disorder (ASD). The results showed a contrasting pattern compared to typically developed (TD) individuals in Study 1, as ASD individuals did not exhibit any significant differences in their performance between faces and non-face objects, despite the absence of the OBA effect in both types of stimuli. The interpretation put forth suggests that these findings can be attributed to the distinct social information processing abilities of individuals with ASD, particularly regarding human faces when compared to TD individuals. Consequently, ASD individuals may similarly process non-face objects to faces, leading to the absence of the OBA pattern induced by both types of stimuli.