DOI: 10.5061/dryad.2jm63xsv2
title: Data from: Peacock spiders prefer image statistics of average natural scenes over those of male ornamentation

description: The origins of preferences that drive the evolution of arbitrary sexual
 signals have been hotly debated for over 150 years. An emerging but
 little-tested theory, efficient coding theory, proposes that male visual
 courtship displays are adapted to pre-existing processing biases shaped by
 the statistical properties of the natural environment. Natural scenes show
 strong spatial correlations with average amplitudes of spatial frequencies
 falling with an average spectral slope of -1, and humans have been shown
 to prefer random amplitude spectrum images that possess similar slopes. It
 has been proposed that other animals may also prefer the statistics of
 their natural environment and that this preference drives the evolution of
 sexual signaling displays. Here, we measure the spectral slope of the male
 display pattern of the Australian peacock jumping spider Maratus spicatus
 and test for a general preference towards that slope. We present spiders
 (male, female and juvenile) with random images of the male slope of -1.7
 compared to a) a shallower slope of -1.0 and b) a steeper slope of -2.3.
 Spiders spent more time oriented towards the shallower slope than towards
 the male slope and spent the same amount of time oriented towards the male
 slope and the steeper slope. Our results indicate that spiders, like
 humans, prefer the average natural slope of -1, suggesting that this is
 likely the slope typically found in their natural habitat. Rather than
 exploiting a potential processing bias, it seems that males have evolved
 slopes that contrast with the visual background to enhance
 conspicuousness.
description: <strong>Mulitspectral imaging
 (salticidVirtualFilters_530nm.mat, imageSets.mat)</strong>
 Multispectral imaging was done using a multisprectral camera
 containing three bird-based optical
 filters (U, M and L) previously described in Tedore and Nilsson (2019) and
 two additional filters previously described in Glenszczyk et al. (2021).
 By taking a
 weighted
 sum of these pre-existing
 camera filters, we calculated computational filters to generate new
 spectral sensitivities matching the spectral sensitivity of the salticid
 green receptor, which typically peaks around 530 nm (De Voe 1975;
 Yamashita and Tateda 1976; Blest et al. 1981; Zurek et al. 2015;
 Glenszczyk et al. 2021). The computational filter technique is further
 described in Tedore and Nilsson (2021) and Glenszczyk et al.
 (2021). <strong>Display distance
 (FirstDanceDist.txt)</strong>
 We analyzed videos of mating
 experiments for the distance at which males first lifted their abdomen
 towards the female using ImageJ on screenshots of the
 video.  <strong>Data for analysing preference for random noise
 image stimuli with spectral slopes of -1.0, 1-.7 and -2.4
 (PreferenceTestInfos.txt, BORIS
 Data)</strong> In each trial, a spider was presented with a
 pair of random images, one of them always representing the spectral slope
 of the courtship display of <em>M. spicatus</em> males (-1.7)
 and the other one representing either a shallower slope of -1.0 or a
 steeper slope of -2.3. Every spider was tested with both combinations at
 intervals of 7 days (±1 day), and the amount of time the spiders looked at
 each image was recorded. Video analysis
 was performed with BORIS software (Friard and Gamba 2016). We scored the
 viewing direction (left image, right image) by following the direction of
 a bright stripe naturally occurring on top of the
 prosoma.
 <strong>Reflection data of grayscale after printing
 (Reflection Grayscale)</strong>
 We measured the reflectance of printed grays
 having RGB values of 0 to 255 in increments of 5. For measurement, printed
 grays were illuminated by a xenon light source (PX-2) channeled through a
 solarization-resistant fiber optic cable oriented 45° relative to the
 surface normal. Reflectance was measured relative to a PTFE diffuse white
 standard (WS-1) using a solarization-resistant fiber optic cable oriented
 normal to the surface being measured. This fiber channeled reflected light
 into a spectrometer (QE Pro; all sourced from Ocean Optics, Ostfildern,
 Germany). 
description: R Core Team. 2019. R: A Language and Environment for Statistical Computing. https://www.R-project.org/. Matlab. 2020. version 9.9.0 (R2020b). Natick, Massachusetts: The MathWorks Inc.