motivation

Your motivation increases as you approach a finish line.

The study using loyalty card stamps to demonstrate the goal gradient effect was conducted by Nunes and Drèze in 2006.

Change the attributed source from Kivetz, Urminsky, and Zheng (2006) to Nunes and Drèze (2006).

You are more likely to work for a finish line than a starting point.

Where this comes from

Study: Kivetz, Urminsky, and Zheng, 2006
What the check found: Kivetz et al. (2006) did study goal progress, but the specific loyalty card/stamp experiment is widely cited as the work of Nunes and Drèze (2006).
Confidence: Solid, with limits

One of these every day, and every one names the study it came from. When a finding is contested, it says so.