Clark Hull
Clark Hull was a psychologist associated with the goal-gradient hypothesis: the idea, first developed in animal learning research, that effort increases as a reward gets closer. His name appears on this site because the 2006 marketing study by Ran Kivetz, Oleg Urminsky and Yuhuang Zheng takes his hypothesis as its starting point and tests it with people.
Who they are
Hull worked in the behaviourist tradition of learning research, in which motivation was studied through how animals approach rewards. This site has not read his original papers, and records his contribution only as the later literature describes it.
This page records only what the papers and their published records state. Biography beyond the cited work is not given here.
Key papers
The goal-gradient hypothesis. Named as Hull's in Kivetz and colleagues' 2006 paper in the Journal of Marketing Research, whose title, "The goal-gradient hypothesis resurrected", refers to it directly. That paper tested the idea in a café reward programme and on a music-rating website, and found customers speeding up as they neared a reward.
Key ideas
The central idea is that distance to a goal shapes effort. Kivetz's study found the same pattern in human customers that the hypothesis had described in animals, and found that progress given rather than earned also sped people up. That is the link between Hull's hypothesis and the endowed progress effect, in which a head start on a loyalty card raises the chance of finishing it.
Sources
- Kivetz, R., Urminsky, O., & Zheng, Y. (2006). The goal-gradient hypothesis resurrected: purchase acceleration, illusionary goal progress, and customer retention. Journal of Marketing Research, 43(1), 39-58. doi:10.1509/jmkr.43.1.39