When Ai, mother of the chimp Amuyu, whose mental feats you reported in this article, appeared in a television documentary a few years ago, I reproduced for myself the number-sequence test she performed and found that, after practice, I could easily outperform her. After reading about Ayumu, I tried the number-recall tests that he and the Kyoto students did. With five digits exposed for 210 milliseconds, I had about a 70 percent success rate—not quite as well as Ayumu, but better than the students. I conclude that conditioning plays a large role in performance.

Merlijn van Veen
Westervoort, The Netherlands