A customizable, low-cost optomotor apparatus: a powerful tool for behaviourally measuring visual capability

Abstract

1. Vision is the dominant sense for many animals, and there is an enormous diversity in visual capabilities. Understanding the visual abilities of a given species can therefore be key for investigating its behaviour and evolution. However, many techniques for quantifying visual capability are expensive, require specialized equipment, or are terminal for the animal. 2. Here, we discuss how to measure the optomotor (or optokinetic) response, an innate response that can be elicited without any training in a wide range of taxa, and which is quantifiable, accessible, and non-invasive, and provide guidance for carrying out optomotor experiments. 3. We provide instructions for building a customizable, programmable optomotor apparatus using 3D-printed and low-cost materials, discuss experimental design considerations for optomotor assays, include a guide that calculates the dimensions of stimuli of varying spatial frequency, and provide a table summarizing experimental parameters in prior optomotor experiments across a range of species. 4. Ultimately, making this simple technique more accessible will allow more researchers to incorporate measures of visual capability into their work. Additionally, the low cost and ease of construction of our apparatus will allow educators in a variety of settings to include optomotor assays in classroom activities or demonstrations. Although here we focus on using optomotor to measure visual acuity—the ability to perceive detail—the apparatus and stimuli described here can be adapted to measure visual capabilities including spectral, contrast, and polarization sensitivity, as well as motion detection, among others.