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PSYC 330: Perception

PSYC 330: Perception. Touch Sensation. The Sense of touch. What does it include? Passive touch (tactile perception) Active touch (haptic perception) The Stimulus Temperature Pressure Pain Movement – kinesthesis. Receptors in the skin: The hardware. Classification: Mechanoreceptors.

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PSYC 330: Perception

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  1. PSYC 330: Perception Touch Sensation

  2. The Sense of touch • What does it include? • Passive touch (tactile perception) • Active touch (haptic perception) • The Stimulus • Temperature • Pressure • Pain • Movement – kinesthesis

  3. Receptors in the skin: The hardware

  4. Classification: Mechanoreceptors • Adaptation rate and size of receptive field • Slow/Small Merkel texture • Slow/Large Ruffini Position/Grasp • Fast/Small Meissner lo freq vibration • Fast/Large Pacinian hi freq vibration

  5. Classification: Thermoreceptors • Warm • Cold

  6. Pain: Nociceptors • Raw nerve endings • A-delta fibers • Myelinated – fast • “insult” pain • C fibers • Not myelinated – slow • “throb” pain

  7. First Stop: Spinal Cord

  8. Onward to brain

  9. The homunculus

  10. Psychophysics of touch • A low-tech experiment….. • Absolute thresholds • LOCATION, LOCATION, LOCATION! • Extremely sensitive • Micrometer resolution • Difference thresholds – spatial resolution • LOCATION, LOCATION, LOCATION!! • Two-point thresholds experiment

  11. Haptic perception • Action for Perception – Exploratory behaviors • Texture – lateral motion • Pressure – hardness • Static contact – temperature • Holding – weight • Enclosure – shape • Contour following – shape

  12. Extracting objects from touch • Visual coding – geometry • Tactile coding – geometry difficult (temporal) • Must integrate information across time to construct shape • Texture more immediately informative • Lederman and Klatzky (1997) • Search for haptic properties that “pop out” (similar to Treisman’s visual search data) • Results: Material properties “pop”, geometric properties don’t • Braille readers – texture, rather than shape

  13. Localizing objects by touch • Localizing requires a frame of personal reference (EGOCENTER) • Much more difficult with touch than with vision • Variable location (eyes always in the same spot – but hands???) • Body image for tactile also varies • http://www.sinauer.com/wolfe2e/chap12/rubberhandF.htm

  14. Now for the really important questions…. • Why can’t we tickle ourselves? • What does “tickle” convey? • Strong reaction • Predators (small ones like spiders) • Self versus Other • Experiment – self tickle versus robot tickle • When delay between direction and robot tickle was short (few msec)  did not tickle • When delay was increased (1/5 s.)  DID tickle

  15. Where am I?

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