Robot speed and body movement were the main focus of another study, also published in PLOS ONE, in which Porfiri teamed with NYU-Poly postdoctoral fellow Sachit Butail and graduate student Tiziana Bartolini. This time, the subject was the zebrafish, and the robot was a free-swimming unit with the coloration, size, aspect ratio, and fin shape of a fertile female member of the species.
The researchers placed the robot in a shared tank with shoals of live zebrafish, aiming to determine if the fish would perceive the robot as a predator, and whether visual cues from the robot could be used to modulate the fishes' social behavior and activity. The team used a remote control to drive the robot in a circular swimming pattern, while varying its tail-beat frequency. For comparison purposes, they also exposed the fish to the robot in a fixed position, beating its tail.
Experiments showed that while the zebrafish clearly did not perceive the swimming robot as one of their ownthey maintained greater distance from the robot than they did to each otherthe robot was still an effective stimulus for modulating their social behavior.
When the robot was held still in the tank, the live fish showed high group cohesion, along with a strong polarizationmeaning the fish were likely to be close to each other and oriented in the same direction. As the robot's tail-beat frequency increased, it had a profound impact on the group's collective behavior, causing a spike in the cohesion and a small but detectable decrease in polarizationthe fish largely milled together and even matched their speeds to that of the robot as it reached a certain tail-beat frequency.
"This shows us that the fish are responding to more than one
|Contact: Kathleen Hamilton|
Polytechnic Institute of New York University