DOI: 10.5061/dryad.stqjq2c1z
title: Comparison of categorical color perception in two Estrildid finches

description: Sensory systems are predicted to be adapted to the perception of important
 stimuli, such as signals used in communication. Prior work has shown that
 female zebra finches perceive the carotenoid-based orange-red coloration
 of male beaks—a mate choice signal—categorically. Specifically, females
 exhibited an increased ability to discriminate between colors from
 opposite sides of a perceptual category boundary than equally-different
 colors from the same side of the boundary. The Bengalese finch, an
 Estrildid finch related to the zebra finch, is black, brown and white,
 lacking carotenoid coloration. To explore the relationship between
 categorical color perception and signal use, we tested Bengalese finches
 using the same orange-red continuum as in zebra finches, and also tested
 how both species discriminated among colors differing systematically in
 hue and brightness. Unlike in zebra finches, we found no evidence of
 categorical perception of an orange-red continuum in Bengalese finches.
 Instead, we found that the combination of chromatic distance (hue
 difference) and Michelson contrast (difference in brightness) strongly
 correlated with color discrimination ability on all tested color pairs in
 Bengalese finches. The pattern was different in zebra finches: this strong
 correlation held only when discriminating between colors from different
 categories, but not when discriminating between colors from within the
 same category. These experiments suggest that categorical perception is
 not a universal feature of avian, or even Estrildid finch, vision. Our
 findings also provide further insights into the mechanism underlying
 categorical perception and are consistent with the hypothesis that
 categorical perception is adapted for signal perception.
description: These behavioral data were collected by EMC, PAG, and DB. The
 data are from a behavioral assay in which birds were provided with a
 foraging grid with 12 wells. On top of six of the wells, we placed colored
 circular discs that were either the same color on both halves (solid) or
 different colors on each half (bicolor): two bicolor discs were used in
 each trial alongside two solid discs of each of the colors comprising the
 bicolor discs. We trained birds to search for food rewards beneath discs
 that they perceived as bicolor. A bird passed a trial if it flipped both
 bicolor discs before flipping any of the solid discs. The data archived
 here have been processed to show the mean "pass frequency," i.e.
 the proportion of trials out of 10 in which birds flipped both bicolor
 discs before flipping any solid discs. Some of the data files show pass
 frequency for each bird for each color combination; others show the mean
 pass frequency across birds (i.e. all zebra finches averaged together) for
 a given color combination. The data also contain  the
 bird ID (a unique identifier for each bird), the number ID of the colors
 on each half of the disc (col1 and col2), and the chromatic distance and
 contrast for the color combination in that trial. Chromatic distance was
 calculated using the Receptor Noise-Limited model (see main text for
 details). Contrast is Michelson contrast (see main text for
 details).
description: "Analysis R Script.R"- This file contains all the code
 necessary to build the training models and<br> do the analysis
 associated with them (i.e. compare them to observed results, generate
 figures).<br> It also has the script for the AIC comparisons between
 models that use a category vs. contrast.
 "Bengalese Finch Data," "Zebra Finch Beak
 Data," and "Zebra Finch Luminance Training Data" support
 the above R script.<br> They are summary datasets (i.e. population
 mean pass frequencies for each color comparison). For example,
 "Bengalese Finch Data.csv" shows<br> mean pass frequency
 across our population of Bengalese finches for each color
 combination.<br> "data" are data regarding zebra finch
 pass frequency on the Beak Set, originally published in [removed for
 double blind review]. "Zebra Finch Luminance Training Data" show
 zebra finch pass frequencies for the Extended Color set.
 "Zebra_finch_raw_beak_set,"
 "Zebra_finch_raw_extended_set," and
 "Bengalese_finch_raw_beak_and_extended_sets" contain<br>
 individual mean pass frequency for each color comparison. These data file
 can be used to create<br> things like Figures 2 and 3 (labeling and
 discrimination) Column descriptions for all data files
 include:<br> bird.ID :    "raw" datasets only. Individual
 bird ID.<br> cat :    Color comparison<br> col1 :    Color 1
 (the redder color) in the color comparison<br> col2 :    Color 2
 (the oranger color) in the color comparison<br> contrast :  
  Michelson contrast between Colors 1 and 2<br> chrom.dist :  
  Chromatic Distance (Delta S) Between Colors 1 and 2<br> pass.freq
 :    Proportion of comparison tasks that birds pass (population
 mean)<br> sd :    Standard deviation of pass frequency<br> n
 :    # of birds that completed comparisons<br> se :    Standard
 error of pass frequency<br> training :    "Bengalese Finch
 Data.csv": Indicates whether a given comparison is used in the
 training model (binary, 0=not included, 1=included)