In SDT, how is an increase in detection sensitivity conceptualised in terms of the movement of the distributions? Is it conceptualised as the signal distribution moving rightward, or as the noise distribution moving leftward?
Technically it can go either way, and both situations would be conceptually and statistically equivalent. But it is conventional to fix the mean of the noise distribution at 0, so that increased discriminability corresponds graphically with the signal+noise distribution moving rightward along the latent axis.