Physiological investigation on tactually perceived objects
Touching objects not only allows us to perceive and discriminate their physical properties (e.g., roughness and softness), it may also evoke affective feelings such as that of pleasantness. There is considerable interest in the commonalities and differences of mechanisms between affective and dis...
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| Format: | Final Year Project |
| Language: | English |
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Nanyang Technological University
2020
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| Online Access: | https://hdl.handle.net/10356/138403 |
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| Institution: | Nanyang Technological University |
| Language: | English |
| Summary: | Touching objects not only allows us to perceive and discriminate their physical properties
(e.g., roughness and softness), it may also evoke affective feelings such as that of
pleasantness. There is considerable interest in the commonalities and differences of
mechanisms between affective and discriminative aspects of touch. Previous psychophysical
studies have demonstrated that physical characteristics of object properties similarly affect
affective and discriminative touch, highlighting the common mechanisms underlying the two
aspects of touch. However, because explicit measures such as subjective ratings can involve
self-report biases, it is unclear about the nature of implicit processing underlying these types
of touch. The present study investigated the psychophysical relationship between
pleasantness and perceived softness through both implicit and explicit measures.
Polyurethane rubber stimuli of different compliances were pressed onto participants’
fingertips at two different forces. Two groups of participants made numerical estimations of
the perceived magnitude of either pleasantness or softness while target muscle activity was
recorded through non-invasive facial electromyography (EMG). Perceived magnitudes of
both pleasantness and softness monotonically increased as a function of increasing object
compliance. However, significant changes in implicit facial EMG responses were only found
when participants were instructed to evaluate pleasantness associated with the contact with
stimuli. These results indicate that contrary to explicit measures, the implicit processing of
stimuli is different between pleasantness and perceived softness and that there might be
partially distinct mechanisms between affective and discriminative touch. Possible
explanations for the findings are discussed. |
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