# peak shift effect

"peak shift effect" is a phrase in psychology of education. I want to know the literal meaning of it. Does it mean "effect caused by shifting peaks" or "effect caused by shifts that are at their peak"? I think the former is OK. Am I right?

Context:

Suppose you’re training a rat to recognize the difference between a square and a rectangle. You present him a square and a rectangle with a switch in front of each. Every time the rat pushes the rectangle switch, you reward him with a piece of cheese. It won’t take long before the rat chooses the rectangle in every single trial.

Now give the rat a choice between the original rectangle and a longer, skinnier rectangle. The rat will strongly prefer the longer, skinnier rectangle. The rat has been trained to do more than pick out one particular rectangle – it has been trained to be rewarded by the concept of “rectangularness” itself. So when it gets something that’s REALLY rectangular – a very long and skinny rectangle – it strongly prefers it. This is the peak shift effect – it occurs when the strength of a particular response is directly proportional to the magnitude of a somewhat simple perceptual cue. Exaggerate that cue, and you can exaggerate the response it elicits.

https://coarsegrained.wordpress.com/2010/08/08/peak-shift-effect/

• "Peak shift", in statistics, is the movement of the "peak" of a frequency graph one direction or another due to some change in parameters. – Hot Licks Dec 6 '15 at 12:37