A respiration rate detector is provided for determining a rate of respiration of an experimental animal. The respiration rate detector includes one or more optical detectors to observe an experimental animal and generate a video signal relating to the experimental animal. A controller is provided to process the video signal to determine an optical flow of the video signal and generate an optical-flow signal, and analyze the optical-flow signal to determine the respiration rate of the experimental animal based on a detected repetitive movement of the experimental animal. The respiration rate is thereby detected without requiring physical contact with the experimental animal.