Figure 1.

Unconditioned light and social preference. a, Schematic of training chamber. The training chamber consists of 14 individual channels, separated on one side by opaque barriers, creating an isolated environment, and on the other side by clear barriers, creating a social environment in which larvae can see their conspecifics. Barriers are slanted at increasing angles toward the outer edges of the testing and training chambers to prevent occlusion of the larvae by the barriers from the camera, situated 11.5 cm above. b, The testing and training chambers were placed in a custom-built, enclosed behavioral box that isolated the larvae from any outside visual or acoustic stimuli. The behavioral box had a semitransparent bottom, onto which different light environments were projected using a computer-controlled projector, while the position of the larvae was captured every 10 s using a camera mounted above. c, Percentage of time spent in light environment during 15 min period by larval zebrafish. Under conditions tested here, larvae showed moderate preference for light, which increases slightly, though not significantly (6 dpf vs 8 dpf, p = 0.091), with age. n = 120–168 per condition. Error bars indicate SEM. d, Percentage of time spent in social environment during 15 min period by larval zebrafish, in both light and dark illumination conditions. Differences between age groups were not statistically significant. n = 27 or 28 per condition. e, Percentage of time spent in social environment during 15 min period by larval zebrafish placed into the training chamber individually, without conspecifics in adjacent channels, in both light and dark conditions. n = 28 per condition.