Seeing and Perceiving

Buildings viewed through the window of another high building sometimes appear to shrink when we walk towards them. We refer to this phenomenon as the 'shrinking building illusion' and conducted a quantitative investigation to elucidate its underlying mechanisms. We created a virtual scenario to test the illusion using three-dimensional computer graphics. After viewing a movie in which the camera moves forward or backward in relation to the buildings, the participants adjusted the size of the test stimulus to the perceived size of the building in the movie...

Summerfield (1987) proposed several accounts of audiovisual speech perception, a field of research that has burgeoned in recent years. The proposed accounts included the integration of discrete phonetic features, vectors describing the values of independent acoustical and optical parameters, the filter function of the vocal tract, and articulatory dynamics of the vocal tract. The latter two accounts assume that the representations of audiovisual speech perception are based on abstract gestures, while the former two assume that the representations consist of symbolic or featural information obtained from visual and auditory modalities...

In visual competition, the perception of ambiguous visual patterns changes spontaneously. Although the process causing this perceptual alternation remains unclear, recent evidence suggests various types of non-visual influences in resolving visual ambiguity. In the present study, we investigated cross-modal modulation of a transient stimulus on visual perceptual stability (i.e., alternation frequency). Participants observed an ambiguous visual figure and reported their perceptual alternations. Concurrently, we presented visual and auditory transient events...

The paper presents an innovative theory of perception of multiple features across and within modalities. Each step is illustrated by an aspect of data from diverse experiments. The theory is that a template or norm of previously configurated features is used to perceive an object in a situation, such as consuming an item of food or drink. A mouthful usually stimulates sight first and then touch, taste and smell, with thermal, irritative, kinaesthetic and auditory patterns often also involved. The visual information also typically includes meanings of words, numbers and pictures...

Although asymmetric colour matching has been widely used in experiments on colour constancy, an exact colour match between objects lit by different chromatic lights is impossible to achieve. We used a modification of this technique, instructing our observers to establish the least dissimilar pair of differently illuminated coloured papers. The stimulus display consisted of two identical sets of 22 Munsell papers illuminated independently by neutral, yellow, blue, green and red lights. The lights produced approximately the same illuminance...

The aim of this study is to investigate whether or not spatial congruency between tactile and auditory stimuli would influence the tactile roughness discrimination of stimuli presented to the fingers or cheeks. In the experiment, when abrasive films were passively presented to the participants, white noise bursts were simultaneously presented from the same or different side, either near or far from the head. The results showed that when white noise was presented from the same side as the tactile stimuli, especially from near the head, the discrimination sensitivity on the cheeks was higher than when sound was absent or presented from a different side...

Self-motion through an environment stimulates several sensory systems, including the visual system and the vestibular system. Recent work in heading estimation has demonstrated that visual and vestibular cues are typically integrated in a statistically optimal manner, consistent with Maximum Likelihood Estimation predictions. However, there has been some indication that cue integration may be affected by characteristics of the visual stimulus. Therefore, the current experiment evaluated whether presenting optic flow stimuli stereoscopically, or presenting both eyes with the same image (binocularly) affects combined visual-vestibular heading estimates...

Object orientation influences visual and haptic recognition differently. This could be caused by the two modalities accessing different object representations or it could be due to differences in how each modality acquires information. These two alternatives were investigated using sequential haptic matching tasks. Matches presented the same object twice. Mismatches presented two similarly-shaped objects. Objects were either both placed at the same orientation or were rotated 90° in depth from each other. Experiment 1 manipulated exploration time to test if longer durations weakened orientation-sensitivity by allowing orientation-invariant representations to be extracted...

When a rectangular wave grating is binocularly viewed with a neutral density filter over one eye, an illusory rotation resembling that of a partially opened Venetian blind is perceived (Cibis and Haber, 1951). Using a binary classification task, in the first experiment, the probability of perceiving a rotation in a given direction was measured as a function of a factorial combination of inter-ocular contrast (see Note 1) and luminance ratios. The probability of a rotation in a given direction decreased monotonically with the luminance of the brighter bars when the grating contains a less than unity contrast...

The spatial-numerical association of response codes (SNARC effect) is a well-documented phenomenon wherein numerical digits spatially bias the selection of a response, with low and high numbers eliciting faster left and right responses, respectively. A host of button press tasks report expression of the SNARC effect for response planning (i.e., reaction time: RT); however, Fischer (2003) reports that the effect can selectively manifest during the movement execution phase (i.e., movement time: MT) of a goal-directed reaching task...

Successful locomotion through space requires precise estimation of the direction and distance travelled. Previous studies have shown that humans can use velocity information arising from visual, vestibular and somatosensory signals to reproduce passive linear displacements. In the present study we investigated whether also associated auditory velocity cues are used for distance estimation. Subjects had to reproduce (active condition) the distance of a previously seen sequence of simulated linear motion (passive condition) across a ground plane...

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Color percept induction in synaesthetes by hearing words was previously shown to involve activation of visual and specifically color processing cortex areas. While this provides a rationale for the origin of the anomalous color percept the question of mechanism of this crossmodal activation remains unclear. We pursued this question with fMRI in color hearing synaesthetes by exposing subjects to words and tones. Brain activations in word condition accompanied by highly reliable color percepts were compared with activations in tone condition with only occasional color percepts and both contrasted to activations in normal subjects under the same stimulus conditions...

Apparent motion can occur within a particular modality or between modalities, in which a visual or tactile stimulus at one location is perceived as moving towards the location of the subsequent tactile or visual stimulus. Intramodal apparent motion has been shown to be affected or 'captured' by information from another, task-irrelevant modality, as in spatial or temporal ventriloquism. Here we investigate whether and how intermodal apparent motion is affected by motion direction cues or temporal interval information from a third modality...

Perception of faces and voices plays a prominent role in human social interaction, making multisensory integration of cross-modal speech a topic of great interest in cognitive neuroscience. How to define potential sites of multisensory integration using functional magnetic resonance imaging (fMRI) is currently under debate, with three statistical criteria frequently used (e.g., super-additive, max and mean criteria). In the present fMRI study, 20 participants were scanned in a block design under three stimulus conditions: dynamic unimodal face, unimodal voice and bimodal face-voice...

While most of the work on stereopsis focuses on geometric disparities, humans also respond to intensity (contrast or luminance) disparities in the absence of geometric disparities. A rectangular-wave grating viewed with an intensity disparity engenders two perceptions: a perceived intensity, and a perceived rotation of the individual bars of the grating (the Venetian blind effect). Measuring perceived intensity and perceived rotation in gratings with intensity disparities, we found that the two degrees of freedom from the intensities presented to each eye are conserved in the form of two perceptions: perceived intensity is related to the sum of the grating intensities and perceived rotation is related to the difference...

Sensory conflict has been used to explain the way we perceive and control our self-motion, as well as the aetiology of motion sickness. However, recent research on simulated viewpoint jitter provides a strong challenge to one core prediction of these theories -- that increasing sensory conflict should always impair visually induced illusions of self-motion (known as vection). These studies show that jittering self-motion displays (thought to generate significant and sustained visual-vestibular conflict) actually induce superior vection to comparable non-jittering displays (thought to generate only minimal/transient sensory conflict)...

The finding that in a patient with visual form agnosia (DF), the performance level varies in a visuomotor letter-posting task and a perceptual orientation matching task was considered as part of the evidence for the perception-action model (Milner and Goodale, 1995). In this study we examined an alternative interpretation of these findings. We specifically tested whether orientation matching and letter posting can be accomplished using different strategies. Sixteen neurologically intact participants were asked to either put cards of different sizes through a target slot of a certain orientation or to simply indicate the slot's orientation...

It has recently been reported that, like most sensory systems, numerosity is subject to adaptation. However, the effect seemed to be limited to numerosity estimation outside the subitizing range. In this study we show that low numbers, clearly in the subitizing range, are adaptable under conditions of high attentional load. These results support the idea that numerosity is detected by a perceptual mechanism that operates over the entire range of numbers, supplemented by an attention-based system for small numbers (subitizing)...

A visual prosthesis provides usable visual information to the patient in the form of phosphenes, that is, punctate photic sensations seen after electrical stimulation. Stimulation via different electrodes results in phosphenes in different positions within the visual field. Simulation studies can provide data on the possible limitations of prosthetic stimulation. We used a head mounted screen to monocularly present constant or flickering light spots of different sizes, or luminance to normally sighted subjects...