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Humans integrate visual and haptic information in a statistically optimal fashion



When a person looks at an object while exploring it with their hand, vision and touch both provide information for estimating the properties of the object. Vision frequently dominates the integrated visual–haptic percept, for example when judging size, shape or position1,2,3, but in some circumstances the percept is clearly affected by haptics4,5,6,7. Here we propose that a general principle, which minimizes variance in the final estimate, determines the degree to which vision or haptics dominates. This principle is realized by using maximum-likelihood estimation8,9,10,11,12,13,14,15 to combine the inputs. To investigate cue combination quantitatively, we first measured the variances associated with visual and haptic estimation of height. We then used these measurements to construct a maximum-likelihood integrator. This model behaved very similarly to humans in a visual–haptic task. Thus, the nervous system seems to combine visual and haptic information in a fashion that is similar to a maximum-likelihood integrator. Visual dominance occurs when the variance associated with visual estimation is lower than that associated with haptic estimation.

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We thank M. Landy for comments on the manuscript; and H. Ernst, X. Moncada, C. Alderson and S. Kashiwada for participating as observers. This research was supported by research grants from Air Force Office of Scientific Research and the National Institutes of Health, and by an equipment grant from Silicon Graphics.

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Competing interests

The authors declare no competing financial interests.

Correspondence to Marc O. Ernst.

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Further reading

Figure 1: Maximum-likelihood estimation integration: two hypothetical situations.
Figure 2: Apparatus and stimuli.
Figure 3: Predictions and experimental data.


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