Psychonomic Bulletin & Review

, Volume 21, Issue 4, pp 976–985 | Cite as

The eyes grasp, the hands see: Metric category knowledge transfers between vision and touch

  • Christian Wallraven
  • Heinrich H. Bülthoff
  • Steffen Waterkamp
  • Loes van Dam
  • Nina Gaißert
Brief Report


Categorization of seen objects is often determined by the shapes of objects. However, shape is not exclusive to the visual modality: The haptic system also is expert at identifying shapes. Hence, an important question for understanding shape processing is whether humans store separate modality-dependent shape representations, or whether information is integrated into one multisensory representation. To answer this question, we created a metric space of computer-generated novel objects varying in shape. These objects were then printed using a 3-D printer, to generate tangible stimuli. In a categorization experiment, participants first explored the objects visually and haptically. We found that both modalities led to highly similar categorization behavior. Next, participants were trained either visually or haptically on shape categories within the metric space. As expected, visual training increased visual performance, and haptic training increased haptic performance. Importantly, however, we found that visual training also improved haptic performance, and vice versa. Two additional experiments showed that the location of the categorical boundary in the metric space also transferred across modalities, as did heightened discriminability of objects adjacent to the boundary. This observed transfer of metric category knowledge across modalities indicates that visual and haptic forms of shape information are integrated into a shared multisensory representation.


Shape Object categorization Vision Haptics Categorization Multisensory representations 


Author note

This research was supported by a PhD stipend from the Max Planck Society; by the WCU (World Class University) program through the National Research Foundation (NRF) of Korea, funded by the Ministry of Education, Science and Technology (Grant No. R31-2008-000-10008-0); by the Basic Science Research Program through the National Research Foundation of Korea, funded by the Ministry of Science, ICT and Future Planning (Grant No. NRF-2013R1A1A1011768); and by the Brain Korea 21 PLUS Program through the National Research Foundation of Korea, funded by the Ministry of Education.


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Copyright information

© Psychonomic Society, Inc. 2013

Authors and Affiliations

  • Christian Wallraven
    • 1
  • Heinrich H. Bülthoff
    • 1
    • 2
  • Steffen Waterkamp
    • 2
  • Loes van Dam
    • 3
  • Nina Gaißert
    • 2
  1. 1.Department of Brain and Cognitive EngineeringKorea UniversitySeongbuk-guKorea
  2. 2.Max Planck Institute for Biological CyberneticsTübingenGermany
  3. 3.University of BielefeldBielefeldGermany

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