Fig. 4. Performance of three pigtail macaques in discriminating between various dilutions of a given odorant and the odourless solvent. Each data point represents the percentage of correct choices from 30 decisions. The three different symbols represent data from each of the three individual animals tested. Filled symbols indicate dilutions that were not discriminated significantly above the chance level (binomial test, P>0.05; chance level shown by broken line).