I think we could all agree that seeing a photo of a person or place is different to seeing that person or place in real life…right? We react differently to photographs. For instance, if there was a picture of your boss, this wouldn’t stop you checking your private emails, would it? But if this person was there, it might. So, recording the behavioural responses to a photograph in humans, couldn’t possibly be representative of how humans would react to the real-life scenario.
However, this is exactly what is happening when measuring responses to photographs in primates. Scientists often use photos to test how animals perceive the world around them. For example, to test whether a dog can tell the difference between a happy versus sad person, they might record whether the dog whimpers more when it sees an image of a person crying versus laughing. Scientists can use photos instead of real-life stimuli to study animal behaviour because they’re cheaper and easier to bring into the lab. But in the absence of depth, smell, and movement, most animals can likely tell the difference between a photo versus the real thing. Behavioural responses to photos are interpreted to reflect how the primate would react in the real-life situation. Thus, recording how animals react to photos may not necessarily tell us how they would behave towards the same scenario in real life. Surprisingly, very few scientists take this problem into consideration when interpreting animals’ responses to photos.
In a recent collaborative study between Living Links and the Language Research Center of Georgia State University, Morton et al. (2016) investigated for the first time whether brown capuchin monkeys react to photos of the alpha male of their group (see below) in the same way as they do in real life.
Typically, lower-ranking capuchins react to the presence of an alpha male by either avoiding them or acting submissively in their presence (e.g. letting the alpha have first dibs on food). By placing food in front of a photo of the alpha male and then doing the same but in front of the real-life alpha, the researchers were able to compare whether the monkeys’ behaviour towards the photo could predict what would happen in reality.
The researchers found that the capuchins did not react to the photo in the same way as they did to the real-life alpha. Thus, a picture of their “boss” (the alpha male) did not fool the monkeys, let alone prevent them from grabbing the food next to the photo.
This study provides scientists with an important cautionary note when using photos to study animal behaviour.
Morton, F. B., Brosnan, S. F., Prétôt, L., Buchanan-Smith, H. M., O’Sullivan, E., Stocker, M., Wilson, V. A. (2016). Using photographs to study animal social cognition and behaviour: Do capuchins’ responses to photos reflect reality? Behavioural Processes, 124, 38-46. doi:10.1016/j.beproc.2015.10.005