Peak–end rule end. The effects of the duration of an experience upon retrospective evaluation are extremely slight. Fredrickson and Kahneman labeled this phenomenon "duration neglect". The peak–end rule is applicable only when an experience has definite beginning and end periods. A 1993 study titled "When More Pain Is Preferred to Less: Adding a Better End" by Kahneman, Fredrickson, Charles Schreiber, and Donald Redelmeier provided groundbreaking evidence for the peak–end rule. Participants were subjected to two different versions of a single unpleasant experience. The first trial had subjects submerge a hand in 14 °C water for 60 seconds. The second trial had subjects
Chain rule a variable "z" depends on the variable "y", which itself depends on the variable "x", so that "y" and "z" are therefore dependent variables, then "z", via the intermediate variable of "y", depends on "x" as well. The chain rule then states, The two versions of the chain rule are related; if formula_4 and formula_5, then In integration, the counterpart to the chain rule is the substitution rule. The chain rule seems to have first been used by Gottfried Wilhelm Leibniz. He used it to calculate the derivative of formula_7 as the composite of the square root function and the