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Alex Holcombe
Polly Barr
• Charlie Ludowici
• Kim Ransley
• Ingrid Van Tongeren
William Ngiam
Fahed Jbarah
• Patrick Goodbourn

action precision
Tactile Motion
Tactile Receptors
Binding, grouping


Skills Checklist
Python Programming
Psychopy/VisionEgg Installation Notes
R analysis,plot,stats
Buttonbox with photocell
Programming Cheat Sheets

12 Aug

  • Easy to rely on temporal freq perception b/c spatial freq constant.

15 Jul

  • Has anyone measured pure stretch adaptation? Makes a MAE?
  • Our effect is orientation selective?
  • someone found lack of correlation between pressure thresholds and motion (displacement) thresholds
  • Konkle et al. could be multimodal integration during test rather than transfer. Or criterion shift when dunno motion, just go with other modality

Tactile reversals following visuo-tactile motion

Dark after light weird reversals when close eyes

  • look in mirror whole time before close eyes, so opposite motion
  • look at periscope or double mirror whole time so doesn't correspond
  • stimulus transients trigger the reversals? Control: Light on for 1s only
  • can't fool stretch receptors? is reason why motion correct at beginning. Or rather, because wider range of spatiotemporal freqs

These notes refer to results by Tatjana Seizova-Cajic, Sarah McIntyre Alex Holcombe . Contact Sarah for information about citing


Jacono M, Gori M, Sciutti A, Sandini G, Burr D, 2008, "Perception of acceleration and deceleration in visual, tactile and visuo-tactile stimuli" Perception 37 ECVP Abstract Supplement, page 49

Perception of acceleration and deceleration in visual, tactile and visuo-tactile stimuli

M Jacono, M Gori, A Sciutti, G Sandini, D Burr

Psychophysical literature suggests that the human visual system is more sensitive to speed than acceleration (the temporal derivative of velocity). However few studies consider tactile perception of acceleration and none of them analyzes the visual - tactile modality. Here we investigated visual, tactile and bimodal perception of acceleration/deceleration by measuring speed discrimination over a wide range of transient speeds (from 6.8 to 454 cm s-1). The stimuli were physical wheels etched with sinewave profile. They could be seen, felt or concurrently seen and felt. Subjects were presented sequentially with the standard stimulus, characterized by a fixed final velocity and variable accelerations and with the comparison test, which reached different final velocities with maximal acceleration. Subjects had to evaluate in 2AFC protocol which interval contained the faster movement, using only visual, only tactile or bimodal information. We found similar PSEs among visual, tactile, and bimodal tasks considering all the different accelerations. Moreover we investigated the difference between deceleration and acceleration and the integration of bimodal signals characterized by opposite direction of motion.

Gori M, Mazzilli G, Sandini G, Burr D, 2008, "A characteristic 'dipper function' for bimodal and unimodal visual and tactile motion discrimination and facilitation between modalities" Perception 37 ECVP Abstract Supplement, page 6 A characteristic 'dipper function' for bimodal and unimodal visual and tactile motion discrimination and facilitation between modalities

M Gori, G Mazzilli, G Sandini, D Burr

We measure bimodal and unimodal visual and tactile velocity discrimination thresholds over a wide range of base velocities and spatial frequencies. The stimuli were two physical wheels etched with a sinewave profile that was both seen and felt, allowing for the simultaneous presentation of visual and haptic velocities, either congruent or in conflict. Stimuli were presented in two separate intervals and subjects reported the faster motion in 2AFC using visual, tactile or bimodal information. We found an improvement in the bimodal thresholds well predicted by the maximum likelihood estimation model and not specific for direction. Interestingly, both bimodal and unimodal thresholds showed a characteristic 'dipper function', with the minimum at a given 'pedestal duration'. The 'dip' occurred over the same velocity range at all spatial frequencies and conditions. Most interestingly, a tactile pedestal facilitated a visual test and vice versa, indicating facilitation between modalities and suggesting that the thresholding of these signals occurs at high levels after crossmodal integration.

p.470 of Blake & Sekuler: in "the temporal cortex, some cells distinguish clearly between tactile stimuli that are expected and those that are not. These cells respond strongly when the skin is touched unexpectedly but fail to respond to the same touch if the individual being touched has been able to see that touch was impending (Mistlin & PErrett 1990)

Failures of tactile localisation

  • absolute much worse than relative
  • Weber described that two points on a part of the skin with greater acuity also are perceived to be separated by more distance (see unused tactile acuity tute slide)
  • cutaneous crawling illusion
  • Helmholtz said that in case of acute toothache patient is uncertain whether the pain is coming from the upper or lower jaw
  • Cain (1973) focused a radiant heat source on either front or back of torso, often had no idea where on their skin heat was delivered

Motion reversals

Delta motion named by Korte occurs when second stimulus much more intense than first. Motion perceived in wrong direction! Also occurs in tactile and auditory (Burtt 1917)

Skin receptors

Receptor depth skin type Fave temp freq* afferent associated sensation
Merkel's disk top skin layers glabrous and hairy? ~1 Hz, <5Hz SA-2, SA-1? pressure
Meissner's corpuscle glabrous ~10 Hz FA-1 flutter
Ruffini corpuscle glabrous and hairy? ~100 Hz  ? stretching
Pacinian corpuscle glabrous? ~400 Hz FA-2 vibration
free nerve ending deep? sometimes on hair, lowww? C,? pain, ache, heat, cold,
  • At high amplitude, all the mechanoreceptors respond to all freqs
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