DOI: 10.5061/dryad.280gb5n17
title: Data from: Motion after-effects induced by dynamic illumination in crab vision

description: Motion detection is an elementary aspect of most animal visual systems.
 However, many environments are prone to background motion which might
 disrupt the ability of visual systems to detect relevant motion cues.
 While in humans, background motion can disrupt the detection of visual
 cues even after the moving background component has ceased, it remains
 unknown whether natural forms of background motion might also affect other
 animal visual systems. Here, we test whether prior exposure to naturally
 occurring ‘caustics’, a form of dynamically moving light patterns commonly
 found in shallow aquatic environments, can have a persisting effect on an
 animal’s motion detection abilities even after the caustic exposure has
 stopped. To do this, we established the response probability of the shore
 crab Carcinus maenas to computer-generated expanding disc stimuli
 mimicking an approaching predator after exposure to either static or
 moving caustic scenes. Prior exposure to moving caustics had a short-term
 persisting effect on visual perception in C. maenas, reducing crabs’
 likelihood to respond to an approaching predator for at least two seconds
 after the moving caustics had ceased. Our study shows that even after an
 exposure period to background motion has ended, the visual response rates
 in C. maenas can still be reduced for a short period owing to the prior
 exposure. While this so-called ‘historical effect’ may derive from an
 adaptation of the crab’s visual system to the caustic background motion,
 we discuss whether it may have survival consequences for this crustacean
 species.
description: # Motion after-effects induced by dynamic illumination in crab vision
 [https://doi.org/10.5061/dryad.280gb5n17](https://doi.org/10.5061/dryad.280gb5n17) ## Description of the data and file structure The two datasets contain the binary response (0 = no response, 1 = responded) of the shore crab Carcinus maenas for approaching predator-like expanding disc stimuli on either static or moving caustic backgrounds.  ### Files and variables #### File: Data\_Experiment1.csv **Description:**  ##### Variables * Trial: Trial number * CrabID: Individual ID for crabs used in this experiment * Size_mm: A individual crab's carapace width in mm * Segment: Each trial comprised the presentation of 8 different treatment (see below). Segment refers to the order number of a treatment within a trial. * Treatment: In total, there were eight treatments, with variations of static or moving caustics in both the exposure and stimulus periods, as well as the contrast (‘visible’ or ‘invisible’) of the expanding disc. We gave each treatment a three-letter code, with the first and second letter stating the caustic condition in the exposure and stimulus period (‘M’ for moving caustics; ‘S’ for static caustics), and the third letter stating the visibility of the expanding disc (‘V’ for a visible disc with a Weber contrast of -0.22; ‘I’ for an invisible disc with a Weber contrast of 0.00). For example, SMV refers to a treatment with an exposure period consisting of static caustics that changes to moving caustics with a visible expanding disc in the stimulus period. * Response: The responses of *C. maenas* to the expanding discs in this experiment were scored as binary response data, with crabs either responding to the expanding disc (1; indicated by slowing down or stopping their movements) or continuing their walking movement and showing no obvious shift in their behaviour (0). #### File: Data\_Experiment2.csv **Description:**  ##### Variables * Trial: Trial number * CrabID: Individual ID for crabs used in this experiment * Size_mm: A individual crab's carapace width in mm * Segment: Each trial comprised the presentation of 8 different treatment (see below). Segment refers to the order number of a treatment within a trial. * Treatment: Each of the eight treatments used in this experiment were assigned an alphanumerical code, following the same system as the previous experiment (see above), but with the addition of a digit referring to the offset (in seconds) at which the disc started to expand (in relation to the start of the stimulus period). For example, MSV3 refers to a treatment with an exposure period consisting of moving caustics that changes to a stimulus period consisting of static caustics with a visible expanding disc that starts expanding 3 seconds after the beginning of the stimulus period. * Response: The responses of *C. maenas* to the expanding discs in this experiment were scored as binary response data, with crabs either responding to the expanding disc (1; indicated by slowing down or stopping their movements) or continuing their walking movement and showing no obvious shift in their behaviour (0). ## Code/software Attached is an R code file which can be used to follow our statistical analysis and plot the data.