Research paper
Sigurdsson V, Saevarsson H, Foxall G. Brand placement and consumer choice: an in-store experiment. Journal of Applied Behavior Analysis. 2009;42(3):741-745. doi:10.1901/jaba.2009.42-741. PMCID: PMC2741065.
Why we cite it
One of few true in-store experiments (not survey or lab-based) demonstrating that shelf position causally affects purchasing. Uses an alternating treatments design across two stores over 4 months, providing clean experimental evidence that middle-shelf (eye-level) placement increases sales relative to high or low shelves. Entrance display amplifies the effect further. The response effort mechanism — less physical and visual effort to notice and reach middle-shelf items — directly parallels the proximity/friction effects in the library's other environment design citations (cpi01, cpi03, cpi10).