Humans integrate visual and
haptic information in a statistically
optimal fashion
Sense of
Touch
Marc O. Ernst* & Martin S. Banks
2002
Hanan Shteingart
Abstract
• Vision and Touch both provide information
– Vision frequently dominates
– in some circumstances the percept is haptic
• They propose a general principle, which
minimizes variance in the final estimate
– determines the degree to which vision or haptics
dominates
– realized by using maximum-likelihood estimation
to combine the inputs.
• Measured the variances associated with
visual and haptic estimation of height
ML Estimation using Modalities
• Perception Equation
– S physical property
– f estimation operation
(neuronal)
– i modalities
• ML estimation
– Independent Gaussian
noise with uniform prior
probability
– Estimator variance
ML Estimation using Modalities
The Experiment
Within Modality Discrimination
Discrimination Threshold
• DT = (PSE) – P-1taller (0.84)
– PSE - point of subjective equality
– normcdf(1)=0.8413
– DT = √2σ2 (due to comparison)
Discrimination Threshold
1
• just-discriminable change
0.9
0.8
0.7
f(x)
0.6
0.5
0.4
0.3
0.2
0.1
0
-2.5
-2
-1.5
-1
-0.5
0
x
0.5
1
1.5
2
2.5
Visual+haptic experiment
Threshold Prediction