Biomedical subjects

Charles Spence

Publications and source records attributed to Charles Spence.

At least 55 records · Page 3Linked to original sources

PubMed2005

Spatiotemporal interactions between audition and touch depend on hand posture.

We report two experiments designed to assess the consequences of posture change on audiotactile spatiotemporal interactions. In Experiment 1, participants had to discriminate the direction of an auditory stream (consisting of the sequential presentation of two tones from different spatial positions) while attempting to ignore a task-irrelevant tactile stream (consisting of the sequential presentation of two vibrations, one to each of the participant's hands). The tactile stream presented to the participants' hands was either spatiotemporally congruent or incongruent with respect to the sounds. A significant decrease in performance in incongruent trials compared with congruent trials was demonstrated when the participants adopted an uncrossed-hands posture but not when their hands were crossed over the midline. In Experiment 2, we investigated the ability of participants to discriminate the direction of two sequentially presented tactile stimuli (one presented to each hand) as a function of the presence of congruent vs incongruent auditory distractors. Here, the crossmodal effect was stronger in the crossed-hands posture than in the uncrossed-hands posture. These results demonstrate the reciprocal nature of audiotactile interactions in spatiotemporal processing, and highlight the important role played by body posture in modulating such crossmodal interactions.

Acoustic Stimulation↗

PubMed2005

Audiovisual prior entry.

It is almost one hundred years since Titchener [E.B. Titchener, Lectures on the Elementary Psychology of Feeling and Attention, Macmillan, New York, 1908] published his influential claim that attending to a particular sensory modality (or location) can speed up the relative time of arrival of stimuli presented in that modality (or location). However, the evidence supporting the existence of prior entry is, to date, mixed. In the present study, we used an audiovisual simultaneity judgment task in an attempt to circumvent the potential methodological confounds inherent in previous research in this area. Participants made simultaneous versus successive judgment responses regarding pairs of auditory and visual stimuli at varying stimulus onset asynchronies (SOAs) using the method of constant stimuli. In different blocks of trials, the participants were instructed to attend either to the auditory or to the visual modality, or else to divide their attention equally between the two modalities. The probability of trials containing intramodal stimulus pairs (e.g., vision-vision or audition-audition) was increased in the focused attention blocks to encourage participants to follow the instructions. The perception of simultaneity was modulated by this attentional manipulation: Visual stimuli had to lead auditory stimuli by a significantly smaller interval for simultaneity to be perceived when attention was directed to vision than when it was directed to audition. These results provide the first unequivocal evidence for the existence of audiovisual prior entry.

Acoustic Stimulation↗

PubMed2005

Visual capture of apparent limb position influences tactile temporal order judgments.

Shore et al. [D.I. Shore, E. Spry, C. Spence, Spatial modulation of tactile temporal order judgments, Perception (submitted for publication)] recently demonstrated that people find it easier to judge which hand is touched first (in a tactile temporal order judgment task) when their hands are placed far apart rather than close together. In the present study, we used a mirror to manipulate the visually perceived distance between participants' hands, while holding the actual (i.e., proprioceptively-specified) distance between them constant. Participants were asked to determine which of two vibrotactile stimuli, one presented to either index finger using the method of constant stimuli, was presented first. Performance was significantly worse (i.e., the JND was larger) when the hands were perceived (due to the mirror reflection) as being close together rather than further apart. These results highlight the critical role that vision plays in influencing the conscious perception of the temporal order of tactile stimuli.

Adult↗

PubMed2005

Assessing the effectiveness of various auditory cues in capturing a driver's visual attention.

This study was designed to assess the potential benefits of using spatial auditory warning signals in a simulated driving task. In particular, the authors assessed the possible facilitation of responses (braking or accelerating) to potential emergency driving situations (the rapid approach of a car from the front or from behind) seen through the windshield or the rearview mirror. Across 5 experiments, the authors assessed the efficacy of nonspatial-nonpredictive (neutral), spatially nonpredictive (50% valid), and spatially predictive (80% valid) car horn sounds, as well as symbolic predictive and spatially presented symbolic predictive verbal cues (the words "front" or "back") in directing the participant's visual attention to the relevant direction. The results suggest that spatially predictive semantically meaningful auditory warning signals may provide a particularly effective means of capturing attention.

Adolescent↗

PubMed2005

Spatial modulation of tactile temporal-order judgments.

We report a series of three experiments designed to examine the effect of posture on tactile temporal processing. Observers reported which of two tactile stimuli, presented to the left and right index fingers (experiments 1-3; or thumb, experiment 3), was perceived first while adopting one of two postures--hands-close (adjacent, but not touching) or hands-far (1 m apart)--in the dark. Just-noticeable differences were significantly smaller in the hands-far posture across all three experiments. In the first two experiments we compared hand versus foot responses and found equivalent advantages for the hands-far posture. In the final experiment the stimuli were presented to either the same or different digit on each hand (index finger or thumb) and we found that only when the same digit on each hand was stimulated was there an advantage for the hands-far posture. The finding that temporal precision was better with greater distance contradicts predictions based on attention-switching models of temporal-order judgments, and also contrasts with results from similar experimental manipulations in other modalities (eg vision). These results provide support for a rapid and automatic process that transforms the representation of a tactile stimulus from a skin-centred reference frame to a more external (eg body-centred or allocentric) one.

Adult↗

PubMed2005

Audio-visual simultaneity judgments.

The relative spatiotemporal correspondence between sensory events affects multisensory integration across a variety of species; integration is maximal when stimuli in different sensory modalities are presented from approximately the same position at about the same time. In the present study, we investigated the influence of spatial and temporal factors on audio-visual simultaneity perception in humans. Participants made unspeeded simultaneous versus successive discrimination responses to pairs of auditory and visual stimuli presented at varying stimulus onset asynchronies from either the same or different spatial positions using either the method of constant stimuli (Experiments 1 and 2) or psychophysical staircases (Experiment 3). The participants in all three experiments were more likely to report the stimuli as being simultaneous when they originated from the same spatial position than when they came from different positions, demonstrating that the apparent perception of multisensory simultaneity is dependent on the relative spatial position from which stimuli are presented.

Adult↗

PubMed2004

Examining the crossmodal consequences of viewing the Müller-Lyer illusion.

For many years, the Müller-Lyer illusion was studied as a purely "visual" illusion, but like many other optical illusions, the evidence now shows that it also occurs when stimuli are presented tactually. In the present study, we investigated whether the visual perception of the illusion would have any crossmodal consequences for haptic perception. The wings-in and wings-out parts of the Müller-Lyer illusion were placed end-to-end, sharing a central fin. This Brentano version of the illusion was presented visually on a screen in front of the participants, who had to compare the "felt" length of two sticks placed on the back of the screen, one behind either part of the illusion. Our results show that the presentation of the visual illusion modified the felt lengths of the sticks presented directly behind the illusion. In particular, the stick presented on the side of space perceived visually as being shorter (behind the wings-in part of the display) was perceived as longer, and vice versa for the stick mounted behind the space perceived visually as longer (behind the wings-out part of the display). These results highlight the crossmodal consequences of the visual perception of the Müller-Lyer illusion for the haptic perception of line length.

Adolescent↗

PubMed2004

Intramodal perceptual grouping modulates multisensory integration: evidence from the crossmodal dynamic capture task.

We investigated the extent to which intramodal visual perceptual grouping influences the multisensory integration (or grouping) of auditory and visual motion information. Participants discriminated the direction of motion of two sequentially presented sounds (moving leftward or rightward), while simultaneously trying to ignore a task-irrelevant visual apparent motion stream. The principles of perceptual grouping were used to vary the direction and extent of apparent motion within the irrelevant modality (vision). The results demonstrate that the multisensory integration of motion information can be modulated by the perceptual grouping taking place unimodally within vision, suggesting that unimodal perceptual grouping processes precede multisensory integration. The present study therefore illustrates how intramodal and crossmodal perceptual grouping processes interact to determine how the information in complex multisensory environments is parsed.

Acoustic Stimulation↗

PubMed2004

Exploring the role of visual perceptual grouping on the audiovisual integration of motion.

In the present study, we explored the role of visual perceptual grouping on audiovisual motion integration, using an adaptation of the crossmodal dynamic capture task developed by Soto-Faraco et al. The principles of perceptual grouping were used to vary the perceived direction (horizontal vs vertical) and extent of apparent motion within the visual modality. When the critical visual stimuli, giving rise to horizontal local motion, were embedded within a larger array of lights, giving rise to the perception of global motion vertically, the influence of visual motion information on the perception of auditory apparent motion (moving horizontally) was reduced significantly. These results highlight the need to consider intramodal perceptual grouping when investigating crossmodal perceptual grouping.

Adult↗

PubMed2004

Audiotactile temporal order judgments.

We report a series of three experiments in which participants made unspeeded 'Which modality came first?' temporal order judgments (TOJs) to pairs of auditory and tactile stimuli presented at varying stimulus onset asynchronies (SOAs) using the method of constant stimuli. The stimuli were presented from either the same or different locations in order to explore the potential effect of redundant spatial information on audiotactile temporal perception. In Experiment 1, the auditory and tactile stimuli had to be separated by nearly 80 ms for inexperienced participants to be able to judge their temporal order accurately (i.e., for the just noticeable difference (JND) to be achieved), no matter whether the stimuli were presented from the same or different spatial positions. More experienced psychophysical observers (Experiment 2) also failed to show any effect of relative spatial position on audiotactile TOJ performance, despite having much lower JNDs (40 ms) overall. A similar pattern of results was found in Experiment 3 when silent electrocutaneous stimulation was used rather than vibrotactile stimulation. Thus, relative spatial position seems to be a less important factor in determining performance for audiotactile TOJ than for other modality pairings (e.g., audiovisual and visuotactile).

Acoustic Stimulation↗

PubMed2004

Extending or projecting peripersonal space with tools? Multisensory interactions highlight only the distal and proximal ends of tools.

The effects of tool-use on the brain's representation of the body and of the space surrounding the body ('peripersonal space') has recently been studied within a number of disciplines in cognitive neuroscience, and is also of great interest to philosophers and behavioural ecologists. To date, most experimental findings suggest that tool-use extends the boundary of peripersonal space-visual stimuli presented at the tips of tools interact more with simultaneous tactile stimuli presented at the hands than visual stimuli presented at the same distance, but not associated with the tools. We studied the proposed extension of peripersonal space by tool-use by measuring the effects of three different tool-use tasks on the integration of visual and tactile stimuli at three distances from participants' hands along two hand-held tools. When the tool-use task required using the shafts or the tips of the tools, visuotactile interactions were stronger at the tips of the tools than in the middle of the shaft. When the handles of the tools were used, however, visuotactile interactions were strongest near the hands and decreased with distance along the tools. These results suggest that tools do not simply 'extend' peripersonal space, but that just the tips of tools actively manipulated in extrapersonal space are incorporated into the brain's visuotactile representations of the body and of peripersonal space.

Adolescent↗

PubMed2004

On the inability to ignore touch when responding to vision in the crossmodal congruency task.

We investigated the extent to which people can selectively ignore distracting vibrotactile information when performing a visual task. In Experiment 1, participants made speeded elevation discrimination responses (up vs. down) to a series of visual targets presented from one of two eccentricities on either side of central fixation, while simultaneously trying to ignore task-irrelevant vibrotactile distractors presented independently to the finger (up) vs. thumb (down) of either hand. Participants responded significantly more slowly, and somewhat less accurately, when the elevation of the vibrotactile distractor was incongruent with that of the visual target than when they were presented from the same (i.e., congruent) elevation. This crossmodal congruency effect was significantly larger when the visual and tactile stimuli appeared on the same side of space than when they appeared on different sides, although the relative eccentricity of the two stimuli within the hemifield (i.e., same vs. different) had little effect on performance. In Experiment 2, participants who crossed their hands over the midline showed a very different pattern of crossmodal congruency effects to participants who adopted an uncrossed hands posture. Our results suggest that both the relative external location and the initial hemispheric projection of the target and distractor stimuli contribute jointly to determining the magnitude of the crossmodal congruency effect when participants have to respond to vision and ignore touch.

Adult↗

PubMed2004

Assessing automaticity in the audiovisual integration of motion.

This study examined the multisensory integration of visual and auditory motion information using a methodology designed to single out perceptual integration processes from post-perceptual influences. We assessed the threshold stimulus onset asynchrony (SOA) at which the relative directions (same vs. different) of simultaneously presented visual and auditory apparent motion streams could no longer be discriminated (Experiment 1). This threshold was higher than the upper threshold for direction discrimination (left vs. right) of each individual modality when presented in isolation (Experiment 2). The poorer performance observed in bimodal displays was interpreted as a consequence of automatic multisensory integration of motion information. Experiment 3 supported this interpretation by ruling out task differences as the explanation for the higher threshold in Experiment 1. Together these data provide empirical support for the view that multisensory integration of motion signals can occur at a perceptual level.

Auditory Perception↗

PubMed2004

Investigating the effect of a transparent barrier on the crossmodal congruency effect.

A transparent barrier, such as a window, protects us from approaching objects (such as flies), although we can still see the objects coming toward us through the occluder. In the present study, we examined whether this potential dissociation between tactile and visual experience introduced by the presence of a transparent barrier also affects visual-tactile interactions in normal participants, as indexed by performance in the crossmodal congruency task. Participants discriminated the elevation of vibrotactile target stimuli (upper vs lower) presented to the left or right hand while trying to ignore visual distractor lights that could independently be presented from upper or lower locations on either the same or the opposite side. A transparent occluder was placed between the vibrotactile targets and the visual stimuli (the barrier occluded the vibrotactile targets in Experiment 1 and the visual distractors in Experiment 2). Vibrotactile elevation discrimination performance was slower and less accurate when the distractor lights were presented from incongruent locations relative to the target (e.g., lower tactile target with upper distractor light). However, there were no significant differences between performance with and without the transparent occluder present. This pattern of results was replicated in Experiment 3 under conditions where the participants were periodically required to reach around the transparent occluder in order to press buttons placed near to the visual distractors. Taken together, these results support recent neuropsychological evidence [Farne et al. (2003) Int J Psychophysiol 50:51-61] suggesting that visual-tactile interactions in peripersonal space are not necessarily modulated by conscious awareness of the impossibility of our hand being touched by the visual stimuli.

Adult↗

PubMed2004

Bouncing or streaming? Exploring the influence of auditory cues on the interpretation of ambiguous visual motion.

When looking at two identical objects moving toward each other on a two-dimensional visual display, two different events can be perceived: the objects can either be seen to bounce off each other, or else to stream through one another. Previous research has shown that the large bias normally seen toward the streaming percept can be modulated by the presentation of an auditory event at the moment of coincidence. However, previous behavioral research on this crossmodal effect has always relied on subjective report. In the present experiment, we used a novel experimental design to provide a more objective/implicit measure of the effect of an auditory cue on visual motion perception. In our study, two disks moved toward each other, with the point of coincidence hidden behind an occluder. When emerging from behind the occluder, the disks (one red, the other blue) could either follow the same trajectory (streaming) or else move in the opposite direction (bouncing). Participants made speeded discrimination responses regarding the side from which one of the disks emerged from behind the occluder. Participants responded more rapidly on streaming trials when no sound was presented and on bouncing trials when the sound was presented at the moment of coincidence. These results provide the first empirical demonstration of the auditory modulation of an ambiguous visual motion display using an implicit/objective behavioral measure of perception.

Acoustic Stimulation↗

PubMed2004

That's my hand! Activity in premotor cortex reflects feeling of ownership of a limb.

When we look at our hands, we immediately know that they are part of our own body. This feeling of ownership of our limbs is a fundamental aspect of self-consciousness. We have studied the neuronal counterparts of this experience. A perceptual illusion was used to manipulate feelings of ownership of a rubber hand presented in front of healthy subjects while brain activity was measured by functional magnetic resonance imaging. The neural activity in the premotor cortex reflected the feeling of ownership of the hand. This suggests that multisensory integration in the premotor cortex provides a mechanism for bodily self-attribution.

Body Image↗

PubMed2004

Early vision impairs tactile perception in the blind.

Researchers have known for more than a century that crossing the hands can impair both tactile perception and the execution of appropriate finger movements. Sighted people find it more difficult to judge the temporal order when two tactile stimuli, one applied to either hand, are presented and their hands are crossed over the midline as compared to when they adopt a more typical uncrossed-hands posture. It has been argued that because of the dominant role of vision in motor planning and execution, tactile stimuli are remapped into externally defined coordinates (predominantly determined by visual inputs) that takes longer to achieve when external and body-centered codes (determined primarily by somatosensory/proprioceptive inputs) are in conflict and that involves both multisensory parietal and visual cortex. Here, we show that the performance of late, but not of congenitally, blind people was impaired by crossing the hands. Moreover, we provide the first empirical evidence for superior temporal order judgments (TOJs) for tactile stimuli in the congenitally blind. These findings suggest a critical role of childhood vision in modulating the perception of touch that may arise from the emergence of specific crossmodal links during development.

Adolescent↗

PubMed2004

The body schema and the multisensory representation(s) of peripersonal space.

In order to guide the movement of the body through space, the brain must constantly monitor the position and movement of the body in relation to nearby objects. The effective 'piloting' of the body to avoid or manipulate objects in pursuit of behavioural goals (Popper & Eccles, 1977, p. 129), requires an integrated neural representation of the body (the 'body schema') and of the space around the body ('peripersonal space'). In the review that follows, we describe and evaluate recent results from neurophysiology, neuropsychology, and psychophysics in both human and non-human primates that support the existence of an integrated representation of visual, somatosensory, and auditory peripersonal space. Such a representation involves primarily visual, somatosensory, and proprioceptive modalities, operates in body part-centred reference frames, and demonstrates significant plasticity. Recent research shows that the use of tools, the viewing of one's body or body parts in mirrors, and in video-monitors, may also modulate the visuotactile representation of peripersonal space.

Journal Article↗