Demonstration of invisible displacement, using an opaque tea strainer as the device to hide the treat.
We used 3 cups to provide 3 hiding locations and limited training to just 9 trials per condition so that we could test the natural occurrence of object representation in the object’s absence by tamarin monkeys. A total of 8 subjects began this set of studies, with 7 completing them. We tested visible displacement, where the monkeys watched us carry a treat to a particular location and deposit it into one of 3 cups. If they tipped over the correct cup, they got to eat the treat. We conducted single, double, and triple visible displacement (where the item is repeatedly hidden and moved with multiple displacements). A catch trial had us touch a final cup that was not used in the hiding, to examine whether monkeys were simply going to the last spot humans touched rather than the true hiding spot. We also tested invisible displacement, where the treat was hidden in an opaque tea strainer and then the strainer was placed in and out of several hiding spots and shown to be empty once it had deposited the treat. Monkeys responded above chance to all of these conditions except for the most difficult one, a double invisible displacement with a catch, where we touched a final cup not involved in the hiding. They can clearly track objects in their absence and can do so over long periods of manipulation and hiding.
Subjects’ Accuracy in Finding Hidden Rewards in Object Permanence
Read the article published on object permanence (2003).
CITATION: Neiworth, J. J., Steinmark, E., Basile, B. M., Wonders, R., Steely, F., & DeHart, C. (2003). A test of object permanence in a new-world monkey species, cotton top tamarins (Saguinus oedipus). Animal cognition, 6(1), 27–37. https://doi.org/10.1007/s10071-003-0162-2