|Carme touching the red square on SMARTA|
At the beginning of this study, we thought that the sound of the conveyer belt inside SMARTA is a good bridge for the ruffed lemurs. We soon learn that it wasn't the case, and that they are probably not paying attention to the sound of the conveyer belt or that they might need to be trained to recognize that the sound of the conveyer belt is a bridge.
As most ruffed lemurs at the Duke Lemur Center are whistle-trained, we have incorporated the whistle as a bridge when we train them to use SMARTA. Here's a short video of Carme doing a red and gray discrimination task. Notice that the moment she touches the red square, a whistle is used to bridge her correct behavior to a craisin that falls off the chute a few seconds later.
Imagine without the whistle. Carme touches the red square and looks to the left. A craisin falls off the chute. The duration between touching the red box and looking to the left only takes a few seconds but that is also how long it takes for SMARTA to dispense a food reward. Carme might then associate looking to the left with a food reward, or any other behaviors she did after touching the red square.
Another positive aspect of using a whistle as a bridge is that we can tell the lemur almost instantaneously that they did a desired behavior as opposed to just giving them a food reward. Without a bridge, it might take more time for a lemur to learn the correct behavior or worse, associating an incorrect behavior with a food reward.