Fig 1.

Theoretical distribution of stereo thresholds in arcsec (A), assuming that the distribution of log-thresholds is normal (B).The mean, median and mode of the log-thresholds are all equal (1.7 log₁₀ arcsec corresponding to 50 arcsec), but the mean of the thresholds is higher (58 arcsec) and the mode is lower (38 arcsec). The conversion relating the mean, medians etc of these two distributions uses the formulae given in Table 2. The values chosen for the mean and SD of the log-distribution do not matter for the present purpose of illustration, but were taken from the values we obtained in 10 and 11-year-olds.