Results Experiment 2: secondary corrections.

A) and B) shows the perceptual noise for the left/right discrimination of the errors before and after making secondary corrective movements and the standard deviation in random error respectively. The median and 25% and 75% percentiles across participants for each condition are indicated by the bars and the error bars respectively (median and 75% percentile for the after correction are 144 mm and approaching infinity respectively). The separate points indicate the results for individual participants (filled symbols indicate performance significantly above chance). C) The measured correction gain vs. the optimal gain for each participant. The predicted optimal gains are generally relatively low which is consistent with participants' behavior. D) Measured ratio between the standard deviations in final endpoint and initial error versus the predicted error ratio. Values below one mean that participants' variance was reduced after making the corrections. Values of one mean no change and values above one mean participants' performance became worse by making corrections. As predicted from the level of perceptual noise and the resulting low correction gains participants hardly improve through correcting.