The study took place at the research station Pipiapan, run by the Universidad Veracruzana, outside of Catemaco, Veracruz, in Mexico. I worked with three female black-handed spider monkeys (Ateles geoffroyi), Piolina, Nanny and Kelly.

To investigate the olfactory detection thresholds of the monkeys, I used a method called a two-choice instrumental conditioning paradigm. The monkeys were presented with two boxes, each with a paper strip attached to it. One paper strip was impregnated with the odorant that I was testing for, the other with an odorless solution. The monkey sniffed both paper strips as much as it liked, and decided which box to open. If it chose the box with the odorized paper strips, it found a food reward inside, but if it chose the wrong box, it received nothing.

Each monkey received three blocks of 10 trials per day. Every day, they were presented with a lower concentration of the odorant, until they could no longer significantly distinguish it from the odorless solution (meaning the had less than 21 out of 30 correct choices). The last concentration that was distinguished above this level was the threshold value.