The processing of subthreshold visual temporal order is transitory and motivation-dependent

Processing a sequence of events is different from encoding the relative order of the elements composing the sequence. Whether order processing arises automatically from the sequential processing of events is yet unknown, however the literature suggests that order processing can occur at an automatic level when the order of stimuli is not detected consciously. In the present study, we aimed to investigate the question of automatic order processing in a difficult visual task where participants identified one among two possible target luminances. The luminance of the targets was contingent on the order of presentation of two visual cues separated by a subthreshold asynchrony. Participants' performance was compared to that in a control condition where the cues were presented synchronously. In a first experiment, participants’ performance benefited from the use of subthreshold order information compared to the control condition, however this facilitation effect was transient and disappeared over the course of the experiment. In a second experiment, we investigated and confirmed the role of motivation, via a monetary incentive, on the previously observed effect. Taken together, our results suggest that the processing of temporal order of sub-threshold asynchronies is possible, although fragile and likely dependent on task requirements.