Memory without awareness: pigeons do not show metamemory in delayed matching to sample.

Metamemory, the ability to report on memory strength, is clearly established in rhesus macaques (Macaca mulatta) by converging evidence from several paradigms. In contrast, A. Inman and S. J. Shettleworth (1999) found no conclusive evidence of metamemory in pigeons. The authors studied pigeons further in 3 paradigms, with multiple tests of metamemory in each. Pigeons encountered a safe alternative to a matching-to-sample test either before (Experiment 2) or concurrently with (Experiment 3) the matching test. Choices of the safe option did not vary consistently with matching accuracy or change in trials with omitted samples in the way predicted for an animal with metamemory. In Experiment 4, confidence ratings following completion of the matching test also did not vary consistently as predicted by metamemory.