1. The problem statement, all variables and given/known data This question is about the line length experiment, which can be seen here: http://people.usd.edu/~schieber/coglab/WebersLaw.html [Broken] Basically you are shown two lines and you have to pick the one that is longer. This is repeated X number of times and the results allow you to calculate the smallest detectable difference in line length, the threshold. 1) If the lines are now made twice as long and the viewing distance stays the same, what will happen to the threshold? 2) If the viewing distance is doubled, but the lines stay the same length, what will happen to the threshold? 3. The attempt at a solution 1) I expect that the threshold is a fixed percentage of line length, so if the line length doubles, so would the threshold. 2) I expect it would double again, but I'm not sure how to back that up.