Abstract
Here, we demonstrate a systematic shift in the perceived location of a tactile stimulus on the arm toward where the eye is looking. Participants reported the perceived position of touches presented between the elbow and the wrist while maintaining eye positions at various eccentricities. The perceived location of the touch was shifted by between 1 and 5 cm (1.9°–9.5° visual angle) by a change in eye position of ±25° from straight ahead. In a control condition, we repeat the protocol with the eyes fixating straight ahead. Changes in attention accounted for only 17% of the shift due to eye position. The pattern of tactile shifts due to eye position was comparable whether or not the arm was visible. However, touches at locations along the forearm were perceived as being farther apart when the arm was visible compared to when it was covered. These results are discussed in terms of the coding of tactile space, which seems to require integration of tactile, visual and eye position information.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Notes
Eye position was not measured since timing and accuracy of the eye’s position were not critical to the experiment.
Upon the request of a reviewer, we tested the hypothesis that the effects reported here were due to a ventriloquism effect between the flashed LED and the touch. As there was a variable delay between the LED offset and tactile onset (100–450 ms), a separate analysis of trials with a short delay (100–275) was compared with long delays (276–450) for both experiment 1 and 2. If the effect reported was due to spatial ventriloquism, then shorter delays should yield stronger effects (larger shifts in position) while longer delays should yield smaller or no effects at all. The average perceived location of the touches (4) at each fixation (4) in each experiment (2) was calculated separately for short and long delays by pooling the participant’s data. Regressions were fitted to each touch across the four fixations separately for the short and long delays (in the same way as is presented in Figs. 2, 3a, and 4a in the paper). If the effects were due to ventriloquism, then there should be larger slopes for shorter delays. A paired samples t test comparing eight short delays and eight long delays (four with vision and four without vision) revealed no significant difference between the slopes for the two delay groups t 7 = 0.29, P = .78).
Since different participants were used in experiment 3 and experiments 1 and 2, this smaller effect could not be statistically tested with a repeated measures design. However, by taking the average slope of the regression lines when the eyes were in a fixed position (Fig. 4a solid black line) and dividing it by the average slope of the regression lines when the eyes changed fixation (Fig. 4a dotted black line), we have calculated that 17% of the effect initially reported as due to eye position, was actually due to the effects of attention.
Similarly, one might argue that the shifted touch might have been due to a response bias. However, the same logic applies since a response bias in this experiment would probably be towards the flashed LED, and should then have appeared in the results of experiment 3. Since the shifted touch effect is minimal in experiment 3, we feel that if a response bias were present it would be relatively minimal in comparison to the size of the effect due to eye position.
References
Austen EL, Soto-Faraco S, Enns JT, Kingstone A (2004) Mislocalizations of touch to a fake hand. Cogn Affect Behav Neurosci 4:170–181
Avillac M, Deneve S, Olivier E, Pouget A, Duhamel JR (2005) Reference frames for representing visual and tactile locations in parietal cortex. Nat Neurosci 8:941–949
Boring EG (1942) Sensation and perception in the history of experimental psychology. Appleton-Century, New York
Cholewiak RW, Collins AA (2003) Vibrotactile localization on the arm: effects of place, space, and age. Percept Psychophys 65:1058–1077
Danilov Y, Tyler M (2005) Brainport: an alternative input to the brain. J Integr Neurosci 4:537–550
de Vries SC, van Erp JB, Kiefer RJ (2009) Direction coding using a tactile chair. Appl Ergon 40(3):477–484
Flach R, Haggard P (2006) The cutaneous rabbit revisited. J Exp Psychol Hum Percept Perform 32:717–732
Graziano MS (2001) A system of multimodal areas in the primate brain. Neuron 29:4–6
Harris LR, Smith AT (2008) The coding of perceived eye position. Exp Brain Res 187:429–437
Ho C, Spence C (2007) Head orientation biases tactile localization. Brain Res 1144:136–141
Ho C, Reed N, Spence C (2006) Assessing the effectiveness of “intuitive” vibrotactile warning signals in preventing front-to-rear-end collisions in a driving simulator. Accid Anal Prev 38:988–996
Kilgard MP, Merzenich MM (1995) Anticipated stimuli across skin. Nature 373:663
Kopinska A, Harris LR (2003) Spatial representation in body coordinates: evidence from errors in remembering positions of visual and auditory targets after active eye, head, and body movements. Can J Exp Psychol 51:23–37
Lewald J (1998) The effect of gaze eccentricity on perceived sound direction and its relation to visual localization. Hear Res 115:206–216
Lewald J, Ehrenstein WH (1996a) Auditory-visual shift in localization depending on gaze direction. Neuroreport 7:1929–1932
Lewald J, Ehrenstein WH (1996b) The effect of eye position on auditory lateralization. Exp Brain Res 108:473–485
Lewald J, Ehrenstein WH (1998) Influence of head-to-trunk position on sound lateralization. Exp Brain Res 121:230–238
Longo MR, Lourenco SF (2007) Space perception and body morphology: extent of near space scales with arm length. Exp Brain Res 177:285–290
Makin TR, Holmes NP, Ehrsson HH (2008) On the other hand: dummy hands and peripersonal space. Behav Brain Res 191:1–10
Pouget A, Deneve S, Duhamel JR (2002) A computational perspective on the neural basis of multisensory spatial representations. Nat Rev Neurosci 3:741–747
Rorden C, Greene K, Sasine G, Baylis G (2002) Enhanced tactile performance at the destination of an upcoming saccade. Curr Biol 12:1429–1434
Rossetti Y, Tadary B, Prablanc C (1994) Optimal contributions of head and eye positions to spatial accuracy in man tested by visually directed pointing. Exp Brain Res 97:487–496
Segond H, Weiss D, Sampaio E (2005) Human spatial navigation via a visuo-tactile sensory substitution system. Perception 34:1231–1249
Stolle AM, Holzl R, Kleinbohl D, Mrsic A, Tan HZ (2004) Measuring point localization errors in spatiotemporal tactile stimulus patterns. In: Proceedings of EuroHaptics, Munich, Germany, 5–7 June, pp 512–515
Wang X, Zhang M, Cohen S, Goldberg ME (2007) The proprioceptive representation of eye position in monkey primary somatosensory cortex. Nat Neurosci 10:640–646
Weerts TC, Thurlow WR (1971) The effects of eye position and expectation on sound localization. Percept Psychophys 9:35–39
Wexler M (2003) Voluntary head movement and allocentric perception of space. Psychol Sci 14:340–346
Acknowledgments
LRH is supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. Vanessa Harrar holds an NSERC postgraduate scholarship.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Harrar, V., Harris, L.R. Eye position affects the perceived location of touch. Exp Brain Res 198, 403–410 (2009). https://doi.org/10.1007/s00221-009-1884-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00221-009-1884-4