Effects of Object Texture on Precontact Movement Time in Human Prehension

Using kinematic data in a precision-grip reaching task, Weir, MacKenzie, Marteniuk, and Cargoe (1991) concluded that prior to contact with an object, its texture does not affect the course of grasping. The present study used their task of reaching for and lifting a slippery-, normal- (polished metal), or rough-surfaced dowel. This occurred under the original, blocked condition, in which textures were held constant within a series of trials, and under a new, randomized condition, in which textures varied randomly from trial to trial. Performance was also examined over more extended periods of practice. Reaction time and precontact movement time were directly measured. In contrast to the results of Weir et al., 1991, reaching for the slippery dowel resulted in slower movement time. This effect was found both early and late in practice for the randomized condition; it was found only in late practice for the blocked condition. These effects can be attributed to the greater geometric and dynamic precision required for lifting a slippery object.     

Tactile roughness perception with a rigid link interposed between skin and surface.

Subjects made roughness judgments of textured surfaces made of raised elements, while holding stick-like probes or through a rigid sheath mounted on the fingertip. These rigid links, which impose vibratory coding of roughness, were compared with the finger (bare or covered with a compliant glove), using magnitude-estimation and roughness differentiation tasks. All end effectors led to an increasing function relating subjective roughness magnitude to surface interelement spacing, and all produced above-chance roughness discrimination. Although discrimination was best with the finger, rigid links produced greater perceived roughness for the smoothest stimuli. A peak in the magnitude-estimation functions for the small probe and a transition from calling more sparsely spaced surfaces rougher to calling them smoother were predictable from the size of the contact area. The results indicate the potential viability of vibratory coding of roughness through a rigid link and have implications for teleoperation and virtual-reality systems.     

Q’Hand: A fully automated apparatus for studying haptic processing of spatially distributed inputs

Q’Hand is an electromechanical system that permits fully automated preparation and presentation of spatially distributed stimulus displays, as well as on-line data acquisition, all under software control. Selected inputs may be presented to any one or combination of the middle three fingertips of both hands. Both accuracy and reaction times are collected on line. Q’Hand was specifically designed to investigate tactile/haptic preattentive and attentive processing of single and multidimensional stimuli. However, it may also be used to study a variety of other research topics, such as pattern recognition, psychophysical issues, and lateralization of somatosensory function. Further, it may be adapted relatively easily for use in clinical settings. For example, with this apparatus, automated psychophysical tests may be designed for the evaluation of the extent of sensory impairment due to peripheral nerve damage otheihander to cortical dysfunction.     

Imagined haptic exploration in judgments of object properties

In Experiment 1, each subject rated a single, named object for its roughness, hardness, temperature, weight, size, or shape. In Experiment 2, each subject compared one pair of objects along the same dimensions. In both studies, a substantial proportion of subjects who judged the first four dimensions imagined a hand making exploratory movements appropriate for the designated information. The proportion of hand-exploration images decreased substantially when judging size or shape, or when judgments could be made readily through general semantic knowledge. The results suggest that the incorporation of haptic exploration into visual imagery provides access to information about haptically accessible object properties.     

Visual mediation and the haptic recognition of two-dimensional pictures of common objects

A set of three experiments was performed to investigate the role of visual imaging in the haptic recognition of raised-line depictions of common objects. Blindfolded, sighted (Experiment 1) observers performed the task very poorly, while several findings converged to indicate that a visual translation process was adopted. These included (1) strong correlation between image-ability ratings (obtained in Experiment 1 and, independently, in Experiment 2) and both recognition speed and accuracy, (2) superior performance with, and greater ease of imaging, two-dimensional as opposed to three-dimensional depictions, despite equivalence in rated line complexity, and (3) a significant correlation between the general ability of the observer to image and obtained imageability ratings of the stimulus depictions. That congenitally blind observers performed the same task even more poorly, while their performance did not differ for two- versus three-dimensional depictions (Experiment 3), provides further evidence that visual translation was used by the sighted. Such limited performance is contrasted with the considerable skill with which real common objects are processed and recognized haptically. The reasons for the general difference in the haptic performance of two- versus three-dimensional tasks are considered. Implications for the presentation of spatial information in the form of tangible graphics displays for the blind are also discussed.     

Journal Reviews

[Authors are asked to send offprints of articles in learned journals on subjects relevant to this section. Offprints of articles in other publications will not normally be reported here, likewise offprints of articles in books since they may constitute part of a volume that can be made the subject matter of a review.]
B ash , K. W. (Bern). 'Regressus ad superos'
B ash , K. W. (Bern). 'Die Dynamik der Aggression (the dynamics of aggression)'
B ash , K. W. (Bern). 'Der unwahrscheinliche Jung'
B ührmann , M. V. (Gansbaai, S. Africa). 'Research into the methods of traditional healers (diviners) amongst the Xhosa-speaking people'
B ührmann , M. V. (Gansbaai, S. Africa). 'Western Psychiatry and the Xhosa Patient.'
B ührmann , M. V. (Gansbaai, S. Africa). 'Dream therapy through the ages'.
D reifuss , G. et al. (Haifa). Article in Shdemot
F ordham , M. (London). 'Die analytische (komplexe) Psychologie in England, article in vol. III of Die Psychologie des 20. Jahrhunderts
F rey -W ehrlin , C. T. (Zürich). 'Die Analytische (komplexe) Psychologie Jung's'
K otschnig , E lined P rys : 'Womanhood in myth and life.'
P aulsen , L. (London). 'Intuition: the unaccountable element'
S cott , W. C lifford , M. (Montreal). 'Remembering sleep and dreams'
'E idon '     

“Improving one’s touch” … and more

Gordon and Cooper (1975) have described an interesting tactile phenomenon. The orientation of undulations on the surface of an object can be detected more accurately when a person moves an intermediate paper over the surface than when the bare fingers are used. Counter to a prediction derived from Gordon and Cooper’s explanation of their results, the present studies show that the apparent roughness of a surface increases when a similar manner of touching is used. The first two experiments confirm the latter observation. To explain the alteration in perceived roughness (and more tentatively, Gordon and Cooper’s own findings), it is proposed that surface roughness (and undulations) are masked by shear forces applied to the skin. Two informal tests and a third experiment support this interpretation. Alternative explanations and a practical application for the blind are also considered.     

Tactile roughness of grooved surfaces: The touching process and effects of macro- and microsurface structure

Ss made magnitude estimates of the perceived roughness of grooved aluminum plates. Two aspects of the touching process were altered and their effects upon roughness examined. Roughness increased with increasing finger force, regardless of whether the S or the E chose the values. Rate of hand motion had a negligible effect on perceived roughness, indicating a roughness constancy and providing further evidence of the relative unimportance of vibratory frequency. The effects of these components of the touching process were discussed in terms of an active-passive continuum rather than a dichotomy. Perceived roughness declined with increasing land width (with narrow grooves), although only over the widest half of the land range; there was no land effect when the grooves were wide. In addition to these macrostructural parameters, the effects of two stimulus production techniques were compared. The discrepancies between the two sets of data were interpreted in terms of the microscopic irregularities of the plate surfaces. The findings were briefly related to an analysis of perceived roughness of grooved surfaces in terms of static deformation of the skin.     

Social and Gendered Readings of Illness Narratives

This essay recognizes that the interactions that define medical care are problematic and that narrative is invoked to overcome these strains. Being grounded in science, medicine, too, might be influenced by a particular world-view that arose in the natural philosophy of the Scientific Revolution. If narrative responds to this sort of medicine, it may retain traces of this mindset. A feminist approach responds to this viewpoint and may used beneficially to analyze both the story of medicine and the stories within medicine. Tensions discussed from this perspective are those between sickness and health and those between patient and provider; also questioned are suitable form(s) of narrative and whose narratives are valued. Suggestions for broadening narrative to address these issues include letting the body speak for itself, overcoming the power differential in the patient/provider interaction and using standpoints to foster a more equal and just medical system.