Attention updates the perceived position of moving objects

Abstract

The information used by conscious perception may differ from that which drives certain actions. A dramatic illusion caused by an object's internal texture motion has been put forward as one example. The motion causes an illusory position shift that accumulates over seconds into a large effect, but targeting of the grating for a saccade (a rapid eye movement) is not affected by this illusion. While this has been described as a dissociation between perception and action, an alternative explanation is that rather than saccade targeting having privileged access to the correct position, a shift of attention that precedes saccades resets the accumulated illusory position shift to zero. In support of this possibility, we found that the accumulation of illusory position shift can be reset by transients near the moving object, creating an impression of the object returning to near its actual position. Repetitive luminance changes of the object also resulted in reset of the accumulation, but less so when attention to the object was reduced by a concurrent digit identification task. Finally, judgments of the object's positions around the time of saccade onset reflected the veridical rather than the illusory position. These results suggest that attentional shifts, including those preceding saccades, can update the perceived position of moving objects and mediate the previously reported dissociation between conscious perception and saccades.

The perceived position of a moving object is reset by temporal, not spatial limits

“…The demonstration movie from Lisi and Cavanagh (2015) shows a gap-triggered reset of linear path to almost all observers. Hand tracing data from 't Hart, Henriques, and Cavanagh (2019) and Nakayama and Holcombe (2020) supports the existence of spontaneous resets along with an otherwise a linear path (see Figure 4). However, the resets, when they do occur, are not very salient and observers are often left with a feeling that the path shifted but without knowing when that happened, so more studies will be required to reach a clear conclusion.…”

“…The double-drift illusion is formed by the accumulation of motion-induced position errors orthogonal to the physical motion path over longer than a second. Studies have shown that the perceived path of this illusion can reset back to its physical location by a temporal gap (Lisi and Cavanagh, 2015) or by attentional distracting events such as transient flashes presented around the stimulus (Nakayama & Holcombe, 2020). Here we examined if such position resets can happen spontaneously, and if so, whether they depend on the time or/and the distance traveled by the double-drift stimulus.…”

“…In contrast, as shown here and in Lisi and Cavanagh (2015), the double-drift accumulates a deviation orthogonal to the motion path for over a second, well beyond the duration over which motion integration operates for saccades. Moreover, it was shown that saccades appear to be immune to the double-drift illusion as eye movements are directed to the physical not the perceived location (Lisi & Cavanagh, 2015; although see Nakayama & Holcombe, 2020). Thus, it is possible that cortical systems with short information integration times such as the saccade system and iconic memory compute target positions in retinotopic coordinates and are not part of the network that computes the perception of the secondlong deviation of the double-drift stimulus.…”

“…Thus, these results imply that there are occasional, random interruptions of accumulation triggered by external events that possibly distract attention. A recent study from Nakayama and Holcombe (2020) proposed that attentional shifts are a possible source for triggering full resets of the perceived path for this stimulus. Interestingly, these random resets bring the perceived location back to the target's physical position either fully or partiallyindicating that some part of the visual system must be keeping track of the physical location even as the perceived location moves farther and farther away from its retinal location.…”

Measuring the double-drift illusion and its resets with hand trajectories

“…The illusion cannot drift continuously away from the physical path forever. It can be disrupted by a temporal break (Lisi & Cavanagh, 2015) or by distracting attention (Nakayama & Holcombe, 2020). These disruptions may cause the perceived path to stay at a fixed offset, travelling parallel to the physical path, or it may return toward the veridical position before resuming the illusory direction (Fig.…”