Apparent haptic movement

When Os were presented with ISO-Hz vibrotactile bursts at two loci on the skin of the thigh and permitted to adjust the time between burst onsets, they reported good apparent movement between the loci. The time between stimulus onsets for optimal movement was found to vary directly with the duration of the stimulus. Replication of the experiment with electrocutaneous stimuli at 1 KHz yielded similar results. Comparison of the data with results from a study of visual apparent movement revealed no difference between the two modalities for the relationship between stimulus onset intervals and stimulus duration. The significance of the results for hypotheses about the processes underlying perception of apparent movement is discussed.     

Tactile apparent movement: The effects of interstimulus onset interval and stimulus duration

The effects of variations in stimulus duration and interstimulus onset interval on ratings of tactile apparent movement were determined for seven Ss with stimulators of very small diameter. Judgments of successiveness and simultaneity were also obtained. It was found that apparent movement increased as a power function of increases in stimulus duration. The function relating tactile apparent movement and stimulus duration was shown to be similar to that obtained by Kolers (1964) for visual apparent movement, lnterstimulus onset interval also had a marked effect on apparent movement, and the optimal interval was influenced by stimulus duration in a manner similar to that reported by Sherrick and Rogers (1966).     

Position uncertainty and the perception of apparent movement

Two experiments compared the perception of apparent movement when the second of two successive stimuli always appeared in the same position and when it varied randomly between two spatial positions. The results of both experiments showed that foreknowledge of the position of the second stimulus does not facilitate the perception of apparent movement. Experiment 2 also clearly showed that the space-time relationships of Korte’s third law of apparent movement does not depend on foreknowledge of the position of the second stimulus. These findings imply that apparent movement in real time occurs after the second stimulus has been registered by the visual system. It suggests that apparent movement involves a delayed decision mechanism that stores the first stimulus, the interstimulus temporal interval, and the second stimulus, and then impletes a motion compatible with the stimulus information.     

Stroboscope motion: Effects of duration and interval1

The quality of stroboscope motion induced by the successive presentation of two illuminated squares obeys two rules. For all stimulus durations shorter than 100 msec, optimal motion occurs when the stimulus onsets differ by about 120 msec. For stimulus durations longer than 100 msec, optimal motion occurs when the second stimulus begins at the termination of the first stimulus. The two rules relating quality of motion to duration suggest a single principle, namely, that the quality depends only on the interval between the visual responses to the two stimuli. The interresponse interval at which motion is optimal is independent of stimulus duration.     

Bilateral apparent haptic movement

When Os are permitted to manipulate the interstimulus onset interval (ISOI) to obtain optimal apparent movement between two ipsilateral vibrotactile stimuli, a consistent quantitative relation between ISOI and stimulus duration appears. The present report describes conditions for movement between contralaterally-placed stimuli, and shows that whereas movement is qualitatively incomplete, the aforementioned relation is still evident. The results are discussed in the light of recent work in both visual apparent movement and complex patterns of stimulation on the skin.     

An aftereffect to discrete stimuli producing apparent movement and succession

After observing the sequential flashing of two lights that produced either the perception of apparent movement or the perception of the succession of two stationary lights, the presentation of the lights in the opposite direction produced the perception of a more rapid apparent movement or of a more rapid succession of the light flashes. These aftereffects suggest the presence of neural structures for the discrimination of sequential changes in spatial position which are subject to adaptation and respond with decreased sensitivity to the repetitive presentation of the two lights in a given spatial direction. The results are interpreted to support the hypothesis that the perception of apparent movement involves the excitation of specific neural mechanisms selectively responsive to sequential changes in stimulus position. An alternative hypothesis is that the perception of apparent movement involves an inference based on the separate registrations of the position of a stimulus at one point in time and the position of that stimulus at an earlier point in time.     

The effect of number of stimulators on the optimal interstimulus onset interval in tactile apparent movement

The effect of variations in the number of sequentially activated electromechanical stimulators on tactile apparent movement was examined in nine subjects. Judgments of successiveness or simultaneity were obtained as well. It was observed that four stimulators produced more frequent reports of apparent movement and resulted in optimal movement at shorter interztimulus onset intervals than did two stimulators, regardless of stimulus duration. Stimulus duration and interstimulus onset interval and their interaction were again found to be important determinants of tactile apparent movement.     

Some temporal factors in the successive comparison of auditory amplitudes.

Under certain conditions the discrimination of successively presented auditory amplitudes appears to be primarily a function of the time intervals between stimulus onsets rather than of either the duration of the stimulus or the silent interval between the tones (interstimulus interval). The results of this study are interpreted in terms of a model containing an acquisition process which continues for a set interval (about 600 msec) subsequent to the onset of the stimulus, even if stimulus offset occurs prior to this time. The onset of another stimulus during this period terminates acquisition. The model also includes a memory process which does not start until acquisition is complete.     

Bottom-up effects modulate saccadic latencies in well-known eye movement paradigm

A well-known eye movement paradigm combines saccades (fast eye movements) with a perceptual discrimination task. At a variable time after the onset of a central arrow cue indicating the target direction [the stimulus onset asynchrony (SOA)], discrimination symbols appear briefly at saccade target and non-target locations. A previous study revealed an unexpected effect of SOA on saccadic latencies: latencies were longer in trials with longer SOAs. It was suggested that this effect reflects a top-down process as observers may wait for the discrimination symbol to appear before executing saccades. However, symbol onsets may also modulate saccade latencies from the bottom-up. To clarify the origin of the SOA effect on latencies in this paradigm, we used a simplified version of the original task plus two new symbol onset conditions for comparison. The results indicate that the modulation of saccadic latencies was not due to a top-down strategy, but to a combination of two opposing bottom-up effects: the symbol onsets at the target location shortened saccade latencies, while symbol onsets at non-target locations lengthened saccade latencies.     

The Perceptual Centre of a Stimulus as the Cue for Synchronization to a Metronome: Evidence from Asynchronies

In tasks where subjects are required to tap in synchrony to a sequence of evenly spaced uniform auditory stimuli (a metronome), tap onsets typically tend to anticipate the metronome's stimulus onsets. We investigated this phenomenon, called “negative asynchrony”, as a function of (1) the duration of the stimuli (1 or 2, 50, 100, and 300 msec), (2) the rise time of the stimuli (0%, 40%, and 80% of stimulus duration), and (3) the interstimulus onset interval duration (500, 700, and 900 msec). The results from three experiments with 28 different subjects showed a significant reduction of the negative asynchrony with longer stimulus durations, and the reduction was not significantly affected by the tempo of the stimulus sequence. Also, a prolongation of the rise time of the stimuli caused an analogous reduction of the negative asynchrony. Findings were taken to suggest that subjects use the perceptual centre rather than physical onset of stimulus as the cue with which to synchronize     

Visual onset expands subjective time

We report a distortion of subjective time perception in which the duration of a first interval is perceived to be longer than the succeeding interval of the same duration. The amount of time expansion depends on the onset type defining the first interval. When a stimulus appears abruptly, its duration is perceived to be longer than when it appears following a stationary array. The difference in the processing time for the stimulus onset and motion onset, measured as reaction times, agrees with the difference in time expansion. Our results suggest that initial transient responses for a visual onset serve as a temporal marker for time estimation, and a systematic change in the processing time for onsets affects perceived time.     

Distorted subjective reports of stimulus onsets under dual-task conditions: Delayed conscious perception or estimation bias?

We investigated whether selecting a response for one task delays the conscious perception of another stimulus (delayed conscious perception hypothesis). In two experiments, participants watched a revolving clock hand while performing two tasks in close succession (i.e. a dual-task). Two stimuli were presented with varying stimulus onset asynchrony (SOA). After each trial, participants separately estimated the onsets of the two stimuli on the clock face. Across two experiments and four conditions, we manipulated response requirements and assessed their impact on perceived stimulus onsets. Results showed that (a) providing speeded responses to the stimuli did lead to greater SOA-dependent misperceptions of both stimulus onsets as compared to a solely perceptual condition, and (b) that response grouping reduced these misperceptions. Overall, the results provide equivocal evidence for the delayed conscious perception hypothesis. They rather suggest that participants’ estimates of the two stimulus onsets are biased by the interval between their responses.     

Temporal summation and reaction time to double-light pulses at suprathreshold levels

Temporal summation of the visual system was studied at suprathreshold levels by measuring reaction time (RT) to the double pulses that were equal in luminance (L) and duration. The RTs were determined as functions of L and the stimulus onset asynchrony (SOA) between the onsets of the two pulses. The relation between RT and L obtained for a given SOA was found to be a power function with the exponent 1/3. The function relating L to SOA was then derived for each of three criterion RTs. The L-SOA relationship indicated partial summation at SOAs shorter than about 20 msec. Inhibition was observed at SOAs longer than about 80 msec. These findings were consistent with the predictions from a temporal integration model.     

Temporal cognition and the phenomenology of time: a multiplicative function for apparent duration

The literature on time perception is discussed. This is done with reference both to the "cognitive-timer" model for time estimation and to the subjective experience of apparent duration. Three assumptions underlying the model are scrutinized. I stress the strong interplay among attention, arousal, and time perception, which is at the base of the cognitive-timer model. It is suggested that a multiplicative function of two key components (the number of subjective time units and their size) should predict apparent duration. Implications for other cognitive domains are drawn, and in particular an analogy is suggested between apparent duration and apparent movement.     

Rapid motor adaptations to subliminal frequency shifts during syncopated rhythmic sensorimotor synchronization

The synchronization of rhythmic arm movements to a syncopated metronome cue was studied in a step-change design whereby small tempo shifts were inserted at fixed time points into the metronome frequency. The cueing sequence involved three stimulus types: (1) target contact in synchrony with the metronome beats, (2) syncopated target contact midway in time between audible beats, and (3) syncopated target contact following either a +2% or -2% change in stimulus frequency. Analysis of normalized and aggregated data revealed that (1) during the syncopation condition the response period showed a rapid adaptation to the frequency-incremented stimulus period, (2) response period was less variable during syncopated movement, (3) mean synchronization error and variability, calculated during syncopation relative to the mathematical midpoint of the stimulus cycle, were reduced during syncopated movements, and (4) synchronization error following the frequency increment showed trends to return linearly to pre-increment values which was fully achieved in the -2% change condition only. The results suggest that frequency entrainment to stimulus period was possible during syncopated movement with the response and stimulus onsets 180 degrees out of phase. Most remarkably, 70-80% of the adaptation of the response period to the new stimulus period was immediately attained during the second half cycle of the syncopated movement. Finally, a mathematical model, based on recursion, was introduced that accurately modeled actual data as a function of the previous stimulus and response intervals and a weighted response of period error and synchronization error, which showed dominance of frequency entrainment over phase entrainment during rhythmic synchronization.     

The auditory redundant signals effect: An influence of number of stimuli or number of percepts?

In two experiments, we examined simple reaction times (RTs) for detection of the onsets and offsets of auditory stimuli. Both experiments assessed the redundant signals effect (RSE), which is traditionally defined as the reduction in RT associated with the presentation of two redundant stimuli, rather than a single stimulus. In Experiment 1, with two identical tones presented via headphones to the left ear, right ear, or both, no RSE was found in responding to tone onsets, but a large RSE was found in responding to their offsets. In Experiment 2, with a pure tone and white noise as the two stimulus alternatives, RSEs were found for responding to both onsets and offsets. The results support the notion that the occurrence of an RSE depends on the number of percepts, rather than the number of stimuli, and on the requirement to respond to stimulus onsets versus offsets. The parallel grains model (Miller & Ulrich, 2003) provides one possible account of this pattern of results.     

The role of occlusion cues in apparent motion

Classical apparent motion stimuli exhibit an inherent ambiguity with respect to the onsets and offsets of the stimulus elements. Sigman and Rock (1974, Perception 3 9-28) presented evidence suggesting that occlusion cues are used to resolve this ambiguity. We present results from experiments designed to further test predictions of this hypothesis. As expected, we found that the apparent motion of a target stimulus is suppressed when a 'moving' occluder is positioned such that it rationalises the onsets and offsets of the stimulus elements constituting the target. Somewhat unexpectedly, though, we also observed a slight tendency for motion suppression under conditions where the target was only partially occluded. The expected motion suppression occurred both with solid occluders and purely virtual Kanizsa-like occluders, although it was not always observed in the latter case. Motion suppression was found to occur over a wide range of stimulus onset asynchronies. Finally, we used binocular disparity cues to test the occlusion account of the motion suppression phenomenon against an alternative explanation in terms of attentional factors. The results are in clear favour of the occlusion account.     

Apparent movement and metacontrast suppression: A decisional analysis

Three test and three mask energies were varied orthogonally and randomly over trials. The stimulus onset asynchrony (ISOA) separating test and mask was varied between trial blocks within each of two display conditions, apparent movement (two-object) and metacontrast (threeobject). Subjects were required to makebrightness judgments of both test and mask energies by responding “bright,” “medium,” or “dim” with respect to the apparent intensity of each stimulus. The accuracy and the coherence lconsistencyt of test judgments were U-shaped functions of SOA for both apparent movement and metacontrast situations. However, the accuracy and the coherence of mask judgments did not vary with SOA for either apparent movement or metacontrast. It was noted that substantially the same results have been reported previously when subjects were required to makecontour judgments. Hence, it is argued that apparent movement and metacontrast suppression are intimately related.     

The subliminal perception of movement and the course of autokinesis

The course of autokinesis is shown to be sensitive to the real movement of a surrounding stimulus. With the supraliminal presentation of this stimulus, apparent movement in a direction opposite to that of the real movement is induced. With the subliminal presentation of the same stimulus the real movement serves to inhibit autokinesis by inducing brief periods of stationarity between the phases of upward and downward apparent movement. The results confirm previous findings that the movement of a stimulus may be discriminated without there being any perceptual (phenomenal) adjunct.     

停表错觉的机制：注意是否为决定因素

通过两个实验探讨了注意是否影响停表错觉（chronostasis）。实验一要求被试在注视时或眼跳后,估计处于眼跳目标或其附近位置的刺激的持续时间;实验二要求被试在眼跳条件下辨别眼跳目标或其附近位置的刺激,以考查两种位置的注意水平。结果表明,眼跳目标位置的注意水平高于其附近位置,而两种位置均可产生停表错觉,且两者的错觉量近似相等。从而说明注意并不影响停表错觉,停表错觉的机制可能是眼跳目标及其附近刺激的知觉提前。