Forward displacements of fading objects in motion: The role of transient signals in perceiving position

Abstract

Visual motion causes mislocalisation phenomena in a variety of experimental paradigms. For many displays objects are perceived as displaced 'forward' in the direction of motion. However, in some cases involving the abrupt stopping or reversal of motion the forward displacements are not observed. We propose that the transient neural signals at the offset of a moving object play a crucial role in accurate localisation. In the present study, we eliminated the transient signals at motion offset by gradually reducing the luminance of the moving object. Our results show that the 'disappearance threshold' for a moving object is lower than the detection threshold for the same object without a motion history. In units of time this manipulation led to a forward displacement of the disappearance point by 175 ms. We propose an explanation of our results in terms of two processes: Forward displacements are caused by internal models predicting positions of moving objects. The usually observed correct localisation of stopping positions, however, is based on transient inputs that retroactively attenuate errors that internal models might otherwise cause. Both processes are geared to reducing localisation errors for moving objects.

Motion Extrapolation in the Central Fovea

“…4 for a graphic outline of this process). According to our account, by weakening the transient signals [22] or eliminating them (i.e. reducing the suppression), as when an object moves into the physiological blind spot [24], forward shifts during motion-termination become manifest again.…”

“…Neural activity of the favored representation is augmented while that of the non-favored one is suppressed. In the flash-terminated condition of the flash-lag effect the predictive representation is suppressed and overwhelmed by the signals due to motion-termination, and consequently the moving object is not seen in the forward shifted position [2], [3], [22]–[24]. It is important to note, however, that the suppression by signals due to failed predictions is likely to be achieved shortly after the ‘stop’ signal due to neural latency.…”

The flash-lag effect and related mislocalizations: Findings, properties, and theories.

“…Thus, moving flashed objects produced a larger flash-lag effect if there was an abmpt change (e.g., onset, offset) in the target than if there was a continuous change in the target. This difference might involve differences between transient and sustained channels (cf Maus & Nijhawan, 2006 tbat underiie processing of abmpt and continuous changes, respectively. Gauch and Kerzel suggested an abmpt change is (mis)bound to a continuous change that follows abmpt change, that onset of a moving target presents an abmpt change akin to a flash, and that asynchronous binding of abmpt and continuous changes produces a flash-lag effect.…”

Going, going, gone: Localizing abrupt offsets of moving objects.

“…In a recent study (Maus & Nijhawan, 2006), off-transients were weakened by gradually decreasing a moving object's luminance until it became invisible. An object disappearing without a strong transient was indeed perceived to vanish in an extrapolated position.…”