Examination of ambiguous stimulus preferences with duration-based measures.

Schlundt et al. (1999) looked at items that came out tied or unclear in a standard approach-based preference test.

They ran the same items again, but this time they let participants interact as long as they wanted and recorded total time spent with each item.

The goal was to see if the extra duration data would clean up the hierarchy and better predict which items would work as reinforcers.

The second, duration-based round produced clearer rankings: items that looked equal before now had a definite high-to-low order.

When the team tested the top items in a reinforcer task, the new hierarchy matched what actually kept responding going.

Kodak et al. (2009) conceptually replicated the idea and showed why it matters: for half of their participants the duration test crowned a different winner than the standard approach test, and only the duration winner functioned as a reinforcer.

Day et al. (2021) extended the method further, proving you can cut the free-operant session to one minute and still get valid data while also reducing problem behavior.

Kang et al. (2013) swept fourteen studies into one review and concluded that duration-based formats belong on the short list of evidence-based tweaks that sharpen reinforcer prediction.

If your client touches two items the same number of times, don’t guess—simply re-run the assessment for a minute or two and score by how long each item stays in their hands. The clearer hierarchy you get is more likely to point to a true reinforcer, saving you from failed sessions and wasted program time.