Microsaccades do not give rise to a conscious feeling of agency for their sensorimotor consequences in visual perception.

Abstract

Feeling of agency (FoA)--the experience of controlling ones actions and their outcomes--has been widely studied for bodily movements. Here, we investigated if microsaccades--small ballistic eye movements--are equally characterized by FoA and if intention mediates this sense of control. We measured FoA via intentional binding, a perceived compression between an action and its effect. In our experiments, we presented a vertically oriented grating, rendered invisible during stable fixation by a rapid temporal phase shift (>60 Hz) that became visible when its retinal motion was slowed down by a microsaccade (active condition). The stimulus was embedded in a clock face and observers reported perceived stimulus timing in each trial. Perceived timing of microsaccade-contingent stimulus perception was compared to the replay of a previous microsaccades retinal consequence (replay condition). Trials without a stimulus were included as a control. To examine the role of intention, we tested this paradigm across two experiments in which observers were either instructed to saccade (intended microsaccades) or fixate (unintended microsaccades). In Experiment 2, no instruction was administered such that any microsaccades were considered spontaneous. Microsaccades--either actively generated or replayed-- consistently rendered the stimulus highly visible compared to trials without such movements-- provided microsaccade direction and peak velocity aligned with the stimuluss motion. Temporal estimates did not differ between the active and replay conditions for any microsaccade type. This result suggests the absence of temporal binding between eye movements and their sensory consequences, and that intention does not facilitate FoA for small eye movements. Significance statementEye movements reflect our decision to closer inspect an aspect of the environment--bodily actions that align our perception with a preceding intention. Here, we investigated if microsaccades--a ballistic, minuscule type of saccade--can be characterized by a feeling of agency: the faint experience of affecting change through intentional actions. In two experiments, we presented an identical stimulus whose visibility was either gaze-contingent (active condition) or independent of eye movements (replay condition). In Experiment 1, we directly compared intended and unintended microsaccades and contrasted them with spontaneous microsaccades in Experiment 2. We found no difference between the active and replay condition for either eye movement type. Our data, hence, does not support feeling of agency for microsaccades. While it remains an open question if large saccades are characterized by feeling of agency, our finding demonstrates that intention is not sufficient to elicit feeling of agency for minuscule motor acts.