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Where a paper is not directly linked from the publications page an abstract is provided here.
We
describe progress towards the provision of realistic cutaneous information to
accompany kinaesthetic input currently available in devices used to haptically
explore virtual objects. A temperature change at the fingertips is made
coincident with “touching” a virtual soft drink can. Pressure orthogonal to
the skin surface contacting the virtual surface can be incorporated in a similar
way.
We used a new
device for comparing active and passive touch that provides a high level of
control over the tasks, and yet also provides
freedom for the explorer. Whether one of active or passive touch was
superior to the other, or whether there was equivalence was determined by the
type of stimulus explored. In terms of latency and accuracy, simple raised line
forms were best explored passively, multiple-element figures were best explored
actively, and for abstract shapes performance in the two exploratory modes was
equivalent. We suggest that cognitive factors account for these findings.
Subjects' fingertips were guided around raised line drawings by a machine we call the Tactile Display System (TDS). The subject's task was to identify, as quickly as possible, what was depicted in the drawings. There were five conditions. In the first, subjects could feel the raised line as they were guided. In the second, guided movements were the same as in condition 1 but subjects felt only the textured paper because the raised line was absent. In the third condition, the paper was completely removed, leaving only kinesthetic cues for the identification task. In the other two conditions (cutaneous information only) the fingertip was held stationary while (a) the raised line drawing was moved beneath it (following the same pattern of movements used in the previous condition) and (b) only the textured paper was moved under the stationary fingertip. Identification of the depictions deteriorated as a function of amount of information present, but performance when kinesthetic cues alone were present, did not differ from performance when cutaneous cues alone were present. The results are discussed in relation to previous research in which the roles of kinesthetic and cutaneous cues are compared. A review of the research comparing
active and passive tactile exploration reveals a lack of agreement about which
is superior. Knowing which is better may help determine the best way to teach
blind people how to use raised line drawings and has potential application in
virtual reality development. It is suggested that the field of haptics lacks
satisfactory definitions of active and passive tactile perception and that
previous research contains potentially confounding variables. A new device is
described and tested – the Tactile Display System (TDS) – that holds
constant many of these confounding factors. The results suggest that passive
exploration is superior in accuracy and latency for simple raised line drawings
such as the outline of a Christmas tree or a heart, that active perception is
better for more complex figures such as a three-letter word, and that there is
no difference between active and passive perception for simple, abstract
pictures. A possible explanation for these findings and further research to test
the explanation are described. The TDS is also capable of breaking
passive-guided exploration into the separate components of kinaesthesis, shear,
and cutaneous information. It was found that kinaesthesis is the most important
factor and that in a task of exploring raised line drawings larger than the size
of the fingerpad, the primary use of cutaneous information may be to guide
exploratory movements.