Because they’ve probably never seen an intoxicated man pick a bar fight with someone much stronger, an inebriated spring breaker leap from a three-story balcony into a hotel pool, or an episode of “Cops,” researchers at the Polytechnic Institute of New York University used zebrafish, robotic predators and a healthy amount of ethanol to gauge how alcohol affects fear.

Although the experiment, published in PLOS ONE, a peer-reviewed, open-access online publication, may shed light on new ways of understanding human anxiety and anxiety-altering substances, it proved most interesting in its novel use of robotic stimuli. Maurizio Porfiri, associate professor of mechanical and aerospace engineering at NYU-Poly, and Simone Macri, from the Istituto Superiore di Sanita in Rome, tested the ability of robots to influence live animals, in this case zebrafish, then added varying concentrations of alcohol, harmless in the doses used, to alter the fishes’ responses.


Pictured: zebrafish (image via Princeton.edu)

“Robots are ideal replacements as independent variables in tests involving social stimuli,” Porfiri said. “They are fully controllable, stimuli can be reproduced precisely each time, and robots can never be influenced by the behavior of the test subjects.” More impressive, they keep experiments constant by reducing the drawbacks of live predator fatigue and unconventional behavior while also proving more humane by reducing the use of live test subjects.  

In the first of three lab scenarios, the researchers, along with students Valentina Cianca and Tiziana Bartolini, placed zebrafish and a robotic Indian leaf fish, a natural predator, in separate compartments of a three-part tank. The entire control group avoided the leaf fish, favoring the third, empty compartment. However, after ethanol was added to the water, the zebrafish began to show changes in behavior, with those exposed to the highest concentration failing to avoid the predatory robot. Porfiri and his colleagues witnessed the same effect using a robotic heron to beat the water’s surface.

Supported by the National Science Foundation, the Honors Center of Italian Universities, and the Mitsui USA Foundation, the researchers think zebrafish may be a suitable replacement for higher-order animals in tests to evaluate emotional responses, while their studies have demonstrated that robots certainly can function as suitable predator replacements. Animal testing likely won’t get PETA’s stamp of approval, but it’s made a large step in a positive direction.