International Journal of Comparative Psychology

Change blindness is a phenomenon in which individuals fail to detect seemingly obvious changes in their visual fields.  Like humans, several animal species have also been shown to exhibit change blindness; however, no species of New World monkey has been tested to date.  Nine capuchins (Sapajus [Cebus] apella) were trained to select whether or not a stimulus changed on a computerized task.  In four phases of testing, consisting of full image changes, subtle occlusion changes, and two levels of feature location changes, the search display and mask durations were systematically varied to determine whether capuchins experienced change blindness and in what contexts.  Only the full image change test yielded significant results, with subjects detecting changes most accurately with longer search displays and, perplexingly, least accurately when there was no mask.  No interactions between search display and mask durations were found in any test phase, suggesting that the relationship between the two parameters may not be important to how capuchins perceive changes.  While it is possible that capuchins do not experience change blindness, we suspect that a mix of experimental design, the difficulty of the task, and the inability to verify how closely the subjects attended to each trial contributed to the lack of significant results.