The term “saccadic chronostasis” refers to the subjective temporal lengthening of a visual stimulus perceived following a saccadic eye movement. In this chapter, we discuss our preferred account of the illusion, which posits that the onset of the postsaccadic stimulus is antedated to a moment just prior to movement initiation, and review supporting evidence that illustrates key characteristics of the illusion, including its dependency on saccade extent. We conclude with a brief discussion of other examples of biased time perception that have been linked to saccadic chronostasis.

Due to neuromuscular delays and the inertial properties of the arm people must consider where a moving object will be in the future if they want to intercept it. We previously proposed that people automatically aim ahead of moving objects they are trying to intercept because they pursue such objects with their eyes, and objects that are pursued with the eyes are mislocalized in their direction of motion. To test this hypothesis we examined whether asking subjects to fixate a static point on a moving target's path, rather than allowing them to pursue the target with their eyes, makes them try to intercept the target at a point that the target has already passed. Subjects could not see their hand during the movement and received no feedback about their performance. They did tend to cross the target's path later – with respect to when the target passed that position – when not pursuing the target with their eyes, but the effect of fixation was much smaller than we predicted, even considering that the subjects could not completely refrain from pursuing the moving target as their hand approached it. Moreover, when subjects first started to move, their hands did not aim farther ahead when pursuing the target than when trying to fixate. We conclude that pursuing the target with one's eyes may be important for interception, but not because it gives rise to localization errors that predict the target's displacement during the neuromuscular delay.

How does the visual system provide us with the perception of a continuous and stable world in the face of the spatial–temporal chaos that characterizes its input? In this chapter we summarize several programs of research that all point to a solution we refer to as object updating. We use this phrase because perceptual continuity seems to occur at an object level (as opposed to an image level or a higher conceptual level) and because our research suggests that the visual system makes a sharp distinction between the formation of new object representations versus the updating of existing object representations. We summarize the research that led us to this view in the areas of masking by object substitution, the flash-lag illusion, response priming, and an illusion of perceptual asynchrony.

Quasi-periodic or “discrete” brain processes are, in theory, susceptible to a phenomenon known in engineering as “temporal aliasing.” When the rate of occurrence of events in the world is fast enough, the perceived direction of these events may be reversed. We have recently demonstrated that, because of a quasi-periodic attentional capture of motion information, continuously moving objects are sometimes perceived to move in the wrong direction (the “continuous Wagon Wheel Illusion”). Using a simple Fourier energy model of motion perception, we established that this type of attentional capture occurs at a rate of about 13 Hz. We verified with EEG recordings that the electrophysiological correlates of this illusion are restricted to a specific frequency band around 13 Hz, over right parietal regions – known for their involvement in directing attention to temporal events. We summarize these results and discuss their implications for visual attention and awareness.

Space and time are modes by which we think and not the conditions in which we live.

The locations of stationary objects appear invariant, although saccadic eye movements shift the images of physically stationary objects on the retina. Two features of this perceptual stability related to saccades are that postsaccadic locations of objects appear invariant relative to their appearance in the presaccadic view, and perception of postsaccadic stimulation is free from interference by remnants of presaccadic stimulation. To generate stability, quantitatively accurate cancellation between retinal input (RI) and extraretinal eye position information (EEPI) must occur, and persisting influences from the presaccadic view must be eliminated. We describe experiments with briefly flashed visual stimuli that have measured (1) the time course of perisaccadic spatial localization, (2) the interfering effects of persisting stimulation prior to the postsaccadic period, (3) the achievement of perceptual stability by removing visual persistence early, and (4) the influence of metacontrast utilizing the normal perisaccadic spatiotemporal distribution of retinal input to prevent interference from visual persistence.

For the steady eye, a generalized cancellation mechanism is analyzed through studying mislocalizations in perceptual orientation and visually guided manual behavior produced by (1) modifying EEPI in observers with experimental partial paralysis (curare) of the extraocular muscles and/or (2) modifying RI by varying visual field orientation (i.e., its pitch and/or roll). The influences of visual pitch and roll derive from the retinal orientations of individual straight lines and their combinations, with the identical lines influencing perceived verticality and elevation. […]

Perceived duration of interstimulus intervals is influenced by the spatial configuration of stimuli. When participants judge the two intervals between a sequence of three stimuli presented with different spatial distances, a greater distance between two stimuli makes the corresponding time interval appear longer (kappa effect, Experiment 1). By employing a choice-reaction time task, we demonstrate that this effect is at least partly due to a facilitating influence of the preceding stimulus on the timing of the subsequent one while the timing of the first stimulus presented is not influenced by the subsequent one. Moreover, reaction times to the subsequent stimulus increased with spatial distance between successive stimuli, and this was valid for a three-stimulus condition (Experiment 2) as well as for a two-stimulus condition (Experiment 3). Thus, our results provide evidence for spatial priming in the temporal kappa effect.

In the “chopstick illusion” (Anstis 1990, 2003) a vertical and horizontal line overlapped to form a cross and followed clockwise circular orbits in counterphase, with one line being at 6 o'clock when the other was at 12 o'clock. The intersection of the lines moved counterclockwise, but it was wrongly perceived as rotating clockwise. This chopstick illusion reveals how moving objects are parsed, based upon the intrinsic and extrinsic terminators of lines viewed through apertures. We conclude that intersections were not parsed as objects, but instead the motion of the terminators (tips) propagated along the lines and was blindly assigned to the intersection. In the similar “sliding rings illusion,” we found that observers could use their eyes to track intersections only when these appeared rigid and not when they appeared to slide. Conclusion – smooth pursuit eye movements are under top-down control and are compelled to rely upon perceptual interpretation of objects.

In the “flash-lag” effect, a static object that is briefly flashed up next to a moving object appears to lag behind the moving object (Nijhawan 2002). We superimposed a flashed spot on a chopsticks intersection that appeared to be moving clockwise along a circular path but was actually moving counterclockwise. We found that the flash appeared displaced clockwise. This was appropriate to the physical, not the subjective direction of rotation, indicating that the flash-lag and the chopstick illusions coexist without interacting. Similarly, the flash-lag effect was unaffected by reversed phi. […]

Anticipation is a hallmark of skilled movements. For example, when removing plates from a loaded tray, the upward force generated by the supporting hand is reduced in anticipation of the reduced load. An adjustment of the postural force occurs as a result of the predicted consequences of the self-initiated action. Although the effect of anticipatory processes is easily discerned in the actions themselves, it is unclear whether these processes also affect our perceptual experience. In this chapter we focus on the relationship between action and the perceptual experience. We begin by reviewing how actions provide reliable predictions of forthcoming sensory information. Following this, we discuss how the anticipation of the time of external events is an important component of action-linked expectations. Finally, we report two experiments that examine how temporal predictions are integrated with the incoming sensory information, evaluating whether this integration occurs in a statistically optimal manner. This predictive process provides the important advantage of compensating for lags in conduction time between peripheral input and the central integration of this information, thus overcoming the physical limitations of sensory channels.

“Real-time sensorimotor control requires the sampling and manipulation not only of parameters representing space but also of those representing time. In particular, when the system itself has inherent processing delays, it invites a situation in which sampled parameters from a peripheral sensor may no longer be valid at the time they are to be used, due to the change in state that took place during the processing delay” (Dominey et al. 1997). In this chapter, we focus on the situation in which a visual stimulus is flashed near the time of a saccade, and the subject's task is to orient the eyes toward the site where the stimulus has been. To perform this task in complete darkness, the subject's brain has to rely on only two signals: retinal error signal and internal eye position signal (iEPS). This is one of the most interesting situations in which the brain has to compute something in the face of specific physical odds (e.g., very long latencies), and we have some hints on how it proceeds. We analyze the time course of the iEPS – which appears quite distorted – using electrical stimulation of brain structures, instead of natural visual stimuli, to provide the goal to be localized. Different hypotheses are then discussed regarding the possible source and possible neural correlate of the iEPS.

When rapidly successive objects or object replicas are presented as sensory streams, a stimulus within a stream is perceptually facilitated relative to an otherwise identical stimulus not within the stream. Experiments on perceptual latency priming and flash-lag have convincingly shown this. Unfortunately, no consensus exists on what is (are) the mechanism(s) responsible for in-stream facilitation. Here, I discuss several alternative explanations: perceptual extrapolation of change in the specific properties of continuous stimulation, time-saving for target processing due to the early microgenetic/formation stages for target being completed on pretarget in-stream items, control of focused selective attention by the onsets of stimulus input, and preparation of the nonspecific perceptual retouch by the preceding nontarget input in stream for the succeeding target input in stream. Revisions are outlined to overcome the explanatory difficulties that the retouch theory has encountered in the face of new phenomena of perceptual dissociation.

There is a delay before sensory information arising from a given event reaches the central nervous system. This delay may be different for information carried by different senses. It will also vary depending on how far the event is from the observer and stimulus properties such as intensity. However, it seems that at least some of these processing time differences can be compensated for by a mechanism that resynchronizes asynchronous signals and enables us to perceive simultaneity correctly. This chapter explores how effectively simultaneity constancy can be achieved, both intramodally within the visual and tactile systems and cross-modally between combinations of auditory, visual, and tactile stimuli. We propose and provide support for a three-stage model of simultaneity constancy in which (1) signals within temporal and spatial windows are identified as corresponding to a single event, (2) a crude resynchronization is applied based on simple rules corresponding to the average processing speed differences between the individual sensory systems, and (3) fine-tuning adjustments are applied based on previous experience with particular combinations of stimuli.

Information about eye position comes from efference copy, a record of the innervation to the extraocular muscles that move the eye and proprioceptive signals from sensors in the extraocular muscles. Together they define extraretinal signals and indicate the position of the eye. By pressing on the eyelid of a viewing eye, the extraocular muscles can be activated to maintain a steady gaze position without rotation of the eye. This procedure decouples efference copy from gaze position, making it possible to measure the gain of the efference copy signal. The gain is 0.61; the gain of oculomotor proprioception, measured by a similar eye press technique, is 0.26. The two signals together sum to only 0.87, leading to the conclusion that humans underestimate the deviations of their own eyes and that extraretinal signals cannot be the mechanisms underlying space constancy (the perception that the world remains stable despite eye movements). The underregistration of eye deviation accounts quantitatively for a previously unexplained illusion of visual direction. Extraretinal signals are used in static conditions, especially for controlling motor behavior. The role of extraretinal signals during a saccade, if any, is not to compensate the previous retinal position but to destroy it. Then perception can begin with a clean slate during the next fixation interval.