Weber–Fechner law states that: "that the subjective sensation is proportional to the logarithm of the stimulus intensity". So maybe the "time estimates" actual

Weber–Fechner law states that: "that the subjective sensation is proportional to the logarithm of the stimulus intensity". So maybe the "time estimates" actually are estimates for expected stimulus intensity. Think about it as 'guessing the level of dread you feel when looking at the project /after/ you finish it'. According to Fechner this should be related to the actual difficulty by a logarithmic law ( at least for humans). These estimates of sensation are than just normal distributed, as one would expect.