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European starlings are capable of discriminating subtle size asymmetries in paired stimuli (2007)
| Venue: | Journal of the Experimental Analysis of Behavior |
| Citations: | 4 - 0 self |
BibTeX
@ARTICLE{Swaddle07europeanstarlings,
author = {John P. Swaddle and Charles and W. Johnson},
title = {European starlings are capable of discriminating subtle size asymmetries in paired stimuli},
journal = {Journal of the Experimental Analysis of Behavior},
year = {2007},
pages = {39--49}
}
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Abstract
Small deviations from bilateral symmetry (fluctuating asymmetries) are cues to fitness differences in some animals. Therefore, researchers have considered whether animals use these small asymmetries as visual cues to determine appropriate behavioral responses (e.g., mate preferences). However, there have been few systematic studies of animals ’ abilities to visually discriminate such minor asymmetries. If the asymmetries cannot be discriminated, fluctuating asymmetry can not be a visual cue. Here, we report an investigation of European starlings ’ (Sturnus vulgaris) abilities to discriminate small size asymmetries. We trained starlings, through operant conditioning in a free-flight aviary, to discriminate achromatic, symmetric paired stimuli from size-matched asymmetric stimuli. By starting the learning process with a large asymmetry and progressing through sequential trials of decreasing asymmetry, we elucidated a behavioral limit to asymmetry discrimination. We found that starlings are capable of discriminating a 10 % size asymmetry. There was weaker evidence for discrimination of 5 % asymmetry but no evidence for signal discrimination at 2.5 % size asymmetry. This level of asymmetry discrimination suggests that many size asymmetry cues in nature can be discriminated by birds. At each level of asymmetry discrimination, we also tested whether starlings could generalize their learned symmetry preference to unreinforced novel images. Consistent with previous findings, we found that starlings could generalize their symmetry preferences.
Keyphrases
european starling paired stimulus subtle size asymmetry visual cue asymmetry discrimination size asymmetry large asymmetry systematic study sequential trial signal discrimination bilateral symmetry appropriate behavioral response previous finding sturnus vulgaris small asymmetry learned symmetry preference mate preference small size asymmetry behavioral limit symmetry preference many size asymmetry cue animal ability size-matched asymmetric stimulus minor asymmetry small deviation operant conditioning free-flight aviary unreinforced novel image
