Realistic humanoids can be a little bit creepy. Apparently, zebrafish feel the same way about robot fish.

In order to study fear in fish, researchers from NYU Polytechnic School of Engineering built a highly realistic, robotic model of a red tiger oscar: a fish often feared by others. They also used a tank divided into three compartments. The first was compartment was left empty, while the second held a live zebrafish. The third compartment had either the robot fish, a real red tiger oscar (a fish that tends to scare others), or a computer animation of an oscar fish.

The live zebrafish weren’t bothered by the animation. But they were scared by both the live red tiger oscar and the robot version. According to Maurizio Porfiri, professor of mechanical and aerospace engineering at the NYU School of Engineering, the live fish spent much less time in the area of the tank where the real oscar fish or the robot was placed. Porfiri also noted that the live zebrafish were more consistently spooked by the robot than the live red tiger oscar.

“Avoidance isn’t the only way we can tell a zebrafish is scared,” said Porfiri. “When these fish are afraid, they also swim differently, and we were surprised to find that the robotic fish could produce an even stronger fear-related response than the actual live predator.”

The researchers claim this is the first study to directly compare the response of zebrafish to both live and robotic predators.