Gaze orienting, and novelty vs. familiarity preference
We have shown a segregation of memory effect on preference choice between object categories: familiarity preference for faces and novelty preference for natural scenes (Shimojo et al., '07, '08; Liao & Shimojo, '08 VSS). It has also been shown that in preference choice, the gaze is biased towards the picture that will be chosen, called “gaze cascade effect” (Shimojo et al., '03 Nat. Neurosci.). Considering that novelty elicits orienting reflex (van Olst, '71), we aim to see whether gaze orienting is directed to novel pictures initially, and whether the initial gaze bias interacts with the later gaze cascade effect between object categories and choices (familiar or novel stimulus). Eye movements were recorded while the subject performed a two-alternative force-choice (2AFC) preference task between an old and a new pictures. The picture that was pre-rated as median attractive was used as the old picture and paired with a new picture in each trial. The results showed that as the trial repeated, the old face was chosen more frequently whereas the new natural scenes were more preferred, replicating our previous findings. Eye movement data showed a general initial gaze bias towards novel pictures, especially for natural scenes, but later on, the gaze patterns differed. For faces, the gaze bias reversed towards familiar pictures to overcome the initial novelty bias in most trials. For natural scenes, on the other hand, the gaze remained on the new picture to bias further towards the final choice. These results suggest that initial gaze bias towards novel pictures contributes to the preference for novelty, but not directly to the preference for familiarity. Indeed, the initial gaze towards novel stimulus is more pronounced in the trials with a final novelty preference for natural scenes, but not for faces.