Support for a theory of memory for event duration must distinguish between test-trial ambiguity and actual memory loss.

Parmenter (1999) looked at pigeon timing tasks. Birds had to remember how long a light stayed on.

The paper says many errors blamed on "bad memory" may come from fuzzy test cues instead.

It warns: check if the retention gap and the gap between trials feel the same to the bird.

No new data were run. The author re-examined past work.

He showed that when the two dark gaps look alike, birds pick the short key by mistake.

The bias vanishes when the gaps look different, so the fault is cue confusion, not forgetting.

McMillan et al. (1999) ran a tight test the same year. They lit up the inter-trial gap and saw the choose-short bias shrink. Both papers say: change the gap, change the error, memory stays fine.

Tranberg et al. (1980) once dimmed the lights during the delay and saw accuracy drop. That paper blamed "interference." Parmenter (1999) reframes it: the light shift simply made the gap feel new, so the bird hesitated. Same data, cleaner story.

Arantes et al. (2008) later showed that birds carry old context into new sessions. Again, choices shifted without any memory loss, backing the idea that external cues, not fading traces, drive the numbers.

Before you say "the learner forgot," ask if your gaps, lights, or room cues look alike. Swap in a clear signal—colored card, beep, or brief blackout—to make the retention interval stand out. You may see better accuracy with no extra drilling.