As Welch puts it, "There is no visual position constancy here, so why should a model originally devised to explain this constancy be appropriate?" (1978: 16).
Moreover, subjects' estimates of the auditory position often differ from their estimates of the visual position.
Our first objective was to determine the extent to which practice enhanced visual position estimates within each training condition.
This suggests taking into account the type of feedback information included in these internal models because the effects of visual, position or force information were non equivalent.
Because perception is corrupted by noise, any sensory stimulus does not reveal the true visual position, but rather induces a distribution of where the stimulus could be, given the stimulus.
It should be noted that these psychophysical biases are relative to a reference position (in Experiment 1, a remembered proprioceptive position and in Experiment 2 a continuous visual position).
