Abstract
Human faces convey a vast amount of information, including but not limited to age, gender, race, emotional state, and attractiveness. The perception of these attributes is important for our social interactions. For this reason, it has been argued that upright faces are a special class of stimuli that are preferentially attended. Preferential processing of fearful or sad expressions in clinical population of anxious individuals or those with severe depression have been reported; however the reports on healthy adult population have not been conclusive and appear to be largely affected by the experimental conditions and response mode. A limitation of laboratory research is that repetitive task performance and behavioural monitoring can restrict the potential impact of biologically-relevant stimuli that would attract attention under more natural conditions. To address this issue, we compare orienting behaviour in two settings: 1) a traditional laboratory task, in which participants make speeded localization responses to face and truck stimuli and 2) stimuli of the same type presented in a waiting area before the experiment began, while participants were unaware that their eye movements were being recorded. In the former setting, participants orientated to faces and trucks similarly (in terms of accuracy and speed); whilst, in the latter setting, participants fixated on faces more frequently, and for greater durations, compared to truck stimuli. These findings indicate that free and unrestricted viewing conditions may be more informative of behaviour than measurements in repeated trials.