Sihan He¹ (), Jay Pratt¹; ¹University of Toronto

In our complex world, we often encounter situations with multiple objects almost simultaneously entering our visual fields. Identifying the temporal order of these stimuli is thus crucial for scene and event segmentation, and guiding task prioritization. Attending to a stimulus has been found to make it perceived earlier than others, with various attention-modulating factors contributing to this advantage (e.g., reward, ownership, perceived spatial depth). However, the impact of affective valences (positivity or negativity), a significant subjective factor influencing attention selection and processing speed, on temporal order perception remains unexplored. To investigate this issue, we used a cueless Temporal Order Judgement (TOJ) task in three experiments. Observers always saw two Chinese characters on the left and right sides of a central fixation, and there was a variable onset delay between the two characters, ranging between 0 ms and 100 ms (in 20 ms intervals). The observers were instructed to indicate which of the two stimuli appeared first. Different pairs of stimuli valences were used in each experiment: positive and negative (Experiment 1), positive and neutral (Experiment 2), and negative and neutral (Experiment 3). The results of the first and second experiments indicated that people reliably perceived positive stimuli earlier than negative stimuli but not neutral stimuli; the third experiment showed that neutral stimuli were perceived earlier when presented with another negative one. Our findings revealed a general temporal prioritization towards semantically positive stimuli modulated by the strength of affective contrasts.