Barry Hughes

Active artificial echolocation and the nonvisual perception of aperture passability

The potential of airborne sonar to provide effective information about three-dimensional (3D) spatial layouts was assessed in four companion experiments. Blindfolded participants, never given visual access to the layout of a large room, were asked to use a sonar device whose output they had never previously encountered to judge the passability (by normal walking) of apertures between two aligned wall panels. Estimates were made from fixed and variable locations, approaches to the apertures were made from orthogonal and oblique angles, and the panels were at different distances and orientations. In each experiment, participants gave evidence of an ability to immediately use the information in structured echoes to make these judgments, though aperture location, approach angles, wall alignment and orientation each had significant effects on performance. The data are compared with performance under visual and nonechoic auditory conditions and are discussed with respect to the notions of potential information and effective information during these perceptually guided tasks.

Texture perception via active touch

Abstract The importance of movement in texture perception by touch has long been appreciated, but problematic issues related to the utilization of information during active touch persist. How is the repeated demonstration of active–passive equivalence in perceptual sensitivity to felt texture to be interpreted? What does such equivalence imply about the source(s) of information used to make perceptual judgements of texture? What sort of perceptual subsystem is organized to recover texture by touch? What is the role played by the action system in this recovery? The seminal observations of David Katz and J.J. Gibson are recounted and contemporary research is described. Several unresolved issues are outlined, as are several approaches by which the availability and utilization of information within this particular perceptual-action subsystem can be empirically studied.

Linguistic and perceptual-motor contributions to the kinematic properties of the braille reading finger

Recordings of the dominant finger during the reading of braille sentences by experienced readers reveal that the velocity of the finger changes frequently during the traverse of a line of text. These changes, not previously reported, involve a multitude of accelerations and decelerations, as well as reversals of direction. We investigated the origin of these velocity intermittencies (as well as movement reversals) by asking readers to twice read out-loud or silently sentences comprising high- or low-frequency words which combined to make grammatical sentences that were either meaningful or nonmeaningful. In a control condition we asked braille readers to smoothly scan lines of braille comprised of meaningless cell combinations. Word frequency and re-reading each contribute to the kinematics of finger movements, but neither sentence meaning nor the mode of reading do so. The velocity intermittencies were so pervasive that they are not easily attributable either to linguistic processing, text familiarity, mode of reading, or to sensory-motor interactions with the textured patterns of braille, but seem integral to all braille finger movements except reversals. While language-related processing can affect the finger movements, the effects are superimposed on a highly intermittent velocity profile whose origin appears to lie in the motor control of slow movements.

On the Nonsmooth, Nonconstant Velocity of Braille Reading and Reversals

Relative to print reading, braille-reading finger movements are held to be of more constant speed, with continuous and exhaustive contact with all words. However, the continuity of movements is intermittent in two distinct ways: (a) readers reverse direction and reread material already encountered and (b) the continual fluctuations of velocity between phases of acceleration and deceleration. We analyze recordings of experienced readers’ encounters with ambiguous sentences predicted to encourage more reversals, and we undertake comparative kinematic analyses of the finger movements during such reading. The data suggest that when reversals are initiated and where they are targeted reflect language-processing demands. However, their kinematic properties are not qualitatively different from those of forward reading. We conclude that how readers of braille move the reading finger—both forward and in reverse—is primarily influenced by the control properties of low-velocity movements and only secondarily by language properties.

Behavioural and Electrophysiological effects related to semantic violations during braille reading

This study investigated the potential to detect event related potentials (ERPs) occurring in response to a specific task in braille reading. This would expand current methodologies for studying the cognitive processes underlying braille reading. An N400 effect paradigm was utilised, whereby proficient blind braille readers read congruent- and incongruent-ending braille sentences. Kinematic and electroencephalography (EEG) data were obtained simultaneously and synchronised. The ERPs differed between the incongruent and congruent sentences in a manner consistent with the N400 effect found with a previous sighted reading paradigm, demonstrating that ERPs can be obtained during braille reading. The frequency of finger reversals and the degree of intermittency in the finger velocity were significantly higher when reading incongruent versus congruent sentence endings. Both reversals and the potential N400 effect may reflect processes involved in semantic unification. These findings have significant implications for the modelling of braille reading. The refinement of the technique will enable other ERPs to be identified and related to behavioural responses, to further our understanding of the braille reading process.

Can haptic feedback reduce the intermittency of slow hand movement velocities

The velocity traces of slow movements are notable for their intermittency: they reveal continuous fluctuations between acceleration and deceleration. We investigate whether this intermittency can be overcome by analyzing haptic feedbacks contribution to any reduction in intermittency. We report an experiment in which blindfolded participants tracked the preferred index finger right- and leftward along raised lines of 8 cm or 16 cm extent at one of three driving frequencies, resulting in movements that ranged from the very slow (mean: 1 cm/s) to the moderately rapid (mean: 32 cm/s). The raised line was punctuated by orthogonal marker lines at 1 cm intervals. We reasoned that if haptic feedback generated by crossing these tangible lines can be used to modulate finger velocity, then requirements to always move “at as smooth and constant a velocity as possible” would be more achievable as practice proceeds. While we found that practice resulted in statistically significant reductions in intermittency, the absolute reductions were only modest. It appears more likely, therefore, that the intermittency in slow movements is not easily obviated by haptic feedback. The precise origin of this intermittency remains uncertain.

Alcohol consumption, dependence and foraging

ABSTRACT Background: Smartphone technology enables treatment providers to deliver targeted outpatient support “on site” in “real time,” but this will require a better understanding of peer networks and substance users’ acquisition of drugs. Objectives: This study sought to understand contextual factors associated with risky levels of alcohol consumption. Methods: A total of 280 participants answered an online survey, completed the AUDIT and indicated their numbers of regular drinking partners, and the number of times and places alcohol was normally consumed. Results: Hazardous drinkers had a greater number of drinking partners and drank alcohol at a greater number of times and locations. Alcohol dependence was associated with alcohol use in more times and places, but was not linked to the numbers of drinking partners. Models drawn from foraging literature were used to describe the data. Conclusions/Importance: Patterns of alcohol foraging could be described by power laws, and such power laws could be used to compare foraging for a range of substances. A consideration of foraging behavior may inform location-aware services targeting risky substance use.

A Multidimensional Scaling Analysis of Texture Gradient Perception via Haptic Exploration

More than one line of research has established roughness as the primary subjective attribute of textured surfaces explored by touch and to be a robust attribute largely unaffected by exploratory velocities or whether exploration is active or passive in nature. Roughness perception appears to be based on sensitivity to spatial distributions of texture elements. We investigated sensitivity to these spatial properties by using texture gradients of known form, explored by one or two fingers, and subjected to multidimensional scaling analysis. Our data suggest that irrespective finger use, perceivers are sensitive to direction and magnitudes of gradients, but not in strict conformance with these physical dimensions, and that a third (but unknown) dimension may also be involved

Skin stimulation, objects of perception, and the blind

The model developed in the target article is not as comprehensive as might be desired on two counts: (1) in that how the transition from proximal stimulation at the skin gives rise to the perception of external objects is taken for granted; and (2) in that another population of participants, the blind, constitute an important group from which we can understand somatosensory processing and neural plasticity.