Movement time can be set by the user

[jyotikab]

If None, sample from a normal distribution with mean =250ms, std = 0.1

[jyotikab]

Done ! A default None leads to movement times to be sampled from N(250,1.5). The other two alternatives are to pass a list: ["constant", 250] or ["mean",250]. The former sets a constant value of 250 for all trials, whereas latter samples from a normal distribution (250,1.5)