The hierarchical order of processes underlying the direction illusion and the direction aftereffect

Motion perception involves the processing of velocity signals through several hierarchical stages of the visual cortex. To better understand this process, a number of studies have sought to localise the neural substrates of two misperceptions of motion direction, the direction illusion (DI) and the direction aftereffect (DAE). These studies have produced contradictory evidence as to the hierarchical order of the processing stages from which the respective phenomena arise. We have used a simple stimulus configuration to further investigate the sequential order of processes giving rise to the DI and DAE. To this end, we measured the two phenomena invoked in combination, and also manually parsed this combined effect into its two constituents by measuring the two phenomena individually in both possible sequential orders. Comparing the predictions made from each order to the outcome from the combined effect allowed us to test the tenability of two models: the DAE-first model and the DI-first model. Our results indicate that DAE-invoking activity does not occur earlier in the motion processing hierarchy than DI-invoking activity. Although the DI-first model is not inconsistent with our data, the possible involvement of non-sequential processing may be better able to reconcile these results with those of previous studies.     

The surface-weight illusion: on the contribution of grip force to perceived heaviness

Previous psychophysical studies have shown that an object, lifted with a precision grip, is perceived as being heavier when its surface is smooth than when it is rough. Three experiments were conducted to assess whether this surface-weight illusion increases with object weight, as a simple fusion model suggests. Experiment 1 verified that grip force increases more steeply with object weight for smooth objects than for rough ones. In Experiment 2, subjects rated the weight of smooth and rough objects. Smooth objects were judged to be heavier than rough ones; however, this effect did not increase with object weight. Experiment 3 employed a different psychophysical method and replicated this additive effect, which argues strongly against the simple fusion model. The whole pattern of results is consistent with a weighted fusion model in which the sensation of grip force contributes only partially to the perceived heaviness of a lifted object.     

The effect of a moving dot transversal on the Poggendorff illusion

In attempting to derive the minimal component of the Poggendorff figure which would still produce an illusion, responses to three types of transversal were measured. One was the customary solid line type; a second type presented the two segments sequentially, alternating between them; and the third consisted of a moving dot which traveled the transversal path. Each transversal was shown with and without verticals, for a total of six conditions. Ten subjects in each condition adjusted the luminous transversal until the segments appeared to be collinear. Figures with verticals present showed a greater magnitude of illusion than those without, and discrepancies for moving dot transversals were greater than those for comparable solid line figures. Since alternating transversals were not significantly larger than solid line figures, it was concluded that the magnitude of the moving dot effect could not be attributed to temporal sequence. An eyemovement hypothesis was suggested instead.     

An illusion of reversed direction in hyperopes

If a subject who is sufficiently farsighted removes his corrective, positive, lenses and looks with one eye from a distance of one or a few meters, at a small lighted area such as the (continuously "on") indicator light of an electric toothbrush, razor, or smoke detector, and if a small object such as a pin is then moved slowly from above to below the subject's eyes (in a plane close to the eye), the subject will perceive the object moving normally from above to below until it encroaches on his view of the lighted area. The object will then be seen to encroach first on the bottom of the lighted area, and as the object continues to move down it will be seen to be moving up across the lighted area, exiting the lighted area at the top. Similarly, an object moved in front of the eye from the subject's left to his right will be seen by the subject to traverse the lighted area in the reverse direction, right to left, even though the subject moves the object himself. Also, while the object is in front of the lighted area, it is perceived as an upside down silhouette having surprisingly clear and sharp edges, and it appears to be located on the lighted area rather than close to the eye where it really is.     

Influence of acoustic context on sound localization: An auditory Roelofs effect

The Roelofs effect is a visual direction illusion: if a large rectangular frame is seen offset from the straight-ahead direction, a small target presented simultaneously is mislocalized in the opposite direction. To investigate whether a similar context illusion might affect auditory localization, we presented a frame of 6 speakers driven with a 300-Hz square wave, 30° left or right of center. The target was a speaker driven with the same waveform, with the two sources in random phase relationship. The target was mislocalized in a direction opposite the frame, an auditory Roelofs effect. A second experiment, using dissimilar sounds for frame and target, yielded no frame-dependent mislocalizations. The effect appeared both in verbal position estimation, a measure of cognitive localization, and in open-loop pointing, a measure of localization in a sensorimotor system. We conclude that audition possesses only one representation of space, in contrast to the two (cognitive and sensorimotor) of vision. The auditory representation corresponds most closely to vision's cognitive system.     

The collapse illusion effect: A semantic-pragmatic illusion of truth and paradox

Abstract

Two Experiments demonstrate the existence of a “collapse illusion”, in which reasoners evaluate Truthteller-type propositions (“I am telling the truth”) as if they were simply true, whereas Liar-type propositions (“I am lying”) tend to be evaluated as neither true nor false. The second Experiment also demonstrates an individual differences pattern, in which shallow reasoners are more susceptible to the illusion. The collapse illusion is congruent with philosophical semantic truth theories such as Kripke's (1975 Kripke, S. 1975. Outline of a theory of truth. The Journal of Philosophy, 72: 690–716. [Crossref], [Web of Science ®] , [Google Scholar]), and with hypothetical thinking theory's principle of satisficing, but can only be partially accounted for by the model theory principle of truth. Pragmatic effects related to sentence cohesion further reinforce hypothetical thinking theory interpretation of the data, although the illusion and cohesion data could also be accounted for within a modified mental model theory.     

The peripheral drift illusion: a motion illusion in the visual periphery

Circularly repeating patches containing sawtooth luminance gradients produce a sensation of motion when viewed in the periphery. Illusory motion is perceived in a dark-to-light direction, but only when one's gaze is directed to different locations around the stimulus, a point outside the display is fixated and the observer blinks, or when the stimulus is sequentially displayed at different locations whilst the observer fixates one point. We propose that the illusion is produced by the interaction of three factors: (i) introducing transients as a result of eye movements or blinks; (ii) differing latencies in the processing of luminance; and (iii) spatiotemporal integration of the differing luminance signals in the periphery.     

Facial expressions modulate the gaze orienting effect on sound localization judgement

Recent studies have shown that cueing eye gaze can affect the processing of visual information, and this phenomenon is called the gaze-orienting effect (visual-GOE). Emerging evidence has shown that the cueing eye gaze also affects the processing of auditory information (auditory-GOE). However, it is unclear whether the auditory-GOE is modulated by emotion. We conducted three behavioural experiments to investigate whether cueing eye gaze influenced the orientation judgement to a sound, and whether the effect was modulated by facial expressions. The current study set four facial expressions (angry, fearful, happy, and neutral), manipulated the display type of facial expressions, and changed the sequence of gaze and emotional expressions. Participants were required to judge the sound orientation after facial expressions and gaze cues. The results showed that the orientation judgement of sound was influenced by gaze direction in all three experiments, and the orientation judgement of sound was faster when the face was oriented to the target location (congruent trials) than when the face was oriented away from the target location (incongruent trials). The modulation of emotion on auditory-GOE was observed only when gaze shifted followed by facial expression (Exp3); the auditory-GOE was significantly greater for angry faces than for neutral faces. These findings indicate that auditory-GOE as a social phenomenon exists widely, and the effect was modulated by facial expression. Gaze shift before the presentation of emotion was the key influencing factor for the emotional modulation in an auditory target gaze-orienting task. Our findings suggest that the integration of facial expressions and eye gaze was context-dependent.     

The effect of a flashing visual stimulus on the auditory continuity illusion

The effect of a visual stimulus on the auditory continuity illusion was examined. Observers judged whether a tone that was repeatedly alternated with a band-pass noise was continuous or discontinuous. In most observers, a transient visual stimulus that was synchronized with the onset of the noise increased the limit of illusory continuity in terms of maximum noise duration and maximum tone level. The smaller the asynchrony between the noise onset and the visual stimulus onset, the larger the visual effect on this illusion. On the other hand, detection of a tone added to the noise was not enhanced by the visual stimulus. These results cannot be fully explained by the conventional theory that illusory continuity is created by the decomposition of peripheral excitation produced by the occluding sound.     

Stability and change in a perspective reversal illusion

A phenomenologieal explanation is presented for the stability and instability of the appearance of the form of objects as a consequence of changes in (1) the spatial position of the observer with respect to the object, and (2) the amount of time the object is observed from a specific spatial position. In support of the explanation, an object was constructed so that it would have multiple appearances when observed continuously from the same viewpoint. The initial appearance of this object when observed from different spatial positions and the constancy over time of these appearances were demonstrated to be in agreement with the theoretical expectations.     

Effects of face configuration change on shape perception: a new illusion

We report two experiments indicating that varying the configuration of face features changes perception of an oval aperture windowing the face: as the eyes and mouth of a frontal-view face photograph are moved vertically toward face boundaries, the oval appears increasingly clongated, taller, and narrower; when eyes and mouth are moved toward the nose, the oval appears increasingly rounder, shorter, and wider. This shape illusion is maximised when faces appear upright within the oval and major face features (eyes, nose, and mouth) appear in their correct relative locations. These results establish that processing of a face configuration can affect perception of a geometric shape that shares visual space with a face. Whether the illusion is face-specific or a special case of a more general geometric illusion is discussed.     

The role of posture in sound localization

Studies of auditory localization revealed that where a subject hears a sound is dependent on both his perceived head position and the auditory cues at his ears. If an error is induced between his true and registered head posture, then errors in his auditory localizations of corresponding size and time course result. The presence of visual information prevents the development of postural errors and, consequently, prevents the development of errors in auditory localization, too. These observations are related to the oculogravic illusion and are interpreted as one aspect of the functioning of a spatial reference system involved in the maintenance of the constancies of auditory and visual detection.     

Constancy and illusion of apparent direction of rotary motion in depth: Tests of a theory

An explanation of apparent direction of rotary motion in depth derived from a general theory of perceptual constancy and illusion is proposed with experimental data in its support. Apparent direction of movement is conceived of as exhibiting-perceptual constancy or illusion as a function of apparent direction of orientation m depth for plane objects and apparent relative depth for three-dimensional objects. Apparent reversals of movement direction represent either regular fluctuations between constancy and illusion of direction as a function of valid and invalid stimuli for orientation, or irregular and random fluctuations in their absence. In three preliminary experiments, the apparent movement direction of plane ellipses was investigated as a function of surface pattern information for orientation, and in Experiment I apparent reversals during 20-revolution trials were studied. In Experiment II, apparent movement direction of 3D elliptical V shapes as a function of surface pattern information for relative depth was investigated. In addition to supporting the explanation proposed, the data offer a resolution of a conflict between different theories of apparent reversal of motion in depth.     

The influence of stimulus bandwidth on localization of sound in space

The ability of listeners, deprived of prominent interaural time and intensity cues, to locate noise bands differing in width was investigated. To minimize binaural cues, we placed the sound source at various positions in the median sagittal plane. To eliminate binaural cues, we occluded one ear. The stimuli consisted of broadband noise and bands of noise centered at 8.0 kHz. The width of the latter ranged from 1.0 to 6.0 kHz. The results from seven listeners showed that localization proficiency for sounds in the median sagittal plane decreased with decreases in bandwidth for both binaural and monaural listening conditions. This function was less orderly for monaural localization of horizontally positioned sounds. Another consequence of a reduction in bandwidth was an increasing tendency of listeners to select certain loudspeakers over others as the source of the sound. A previous finding showing that localization of sound in the median sagittal plane is more accurate when listening binaurally rather than monaurally was confirmed.     

The role of a change heuristic in judgments of sound duration

The present study investigated whether the quality of a frequency change within a sound (i.e., smooth vs. abrupt) would influence perception of its duration. In three experiments, participants were presented with two consecutive sounds on each of a series of trials, and their task was to judge whether the second sound was longer or shorter in duration than the first. In Experiment 1, participants were more likely to judge sounds consisting of a smooth and continuous change in frequency as longer in duration than sounds that maintained a constant frequency. In Experiment 2, the same bias was observed for sounds incorporating an abrupt change in frequency, but only when the frequency change was relatively small. The results of Experiment 3 suggested that the application of a change heuristic when generating duration judgments depends on the perception of change as originating from a single, integrated perceptual object.