CATPERCCOL · Perception of signals under varying conditions: implications of proportional processing of signal magnitude for signal design
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2019-08-15 → 2021-08-14
- EU contribution
- €183,455
- Participants
- 1
- Scheme
- MSCA-IF
Lines connect the coordinator with its partners.
Results in brief
Perception of signals under varying conditions: implications of proportional processing of signal magnitude for signal design
Animals assess one another using signals in contexts that are critically important for survival and reproduction, such as mate choice. Many animal signals vary along a continuum, and this variation reflects variation in the quality of the signaller. An implicit assumption in most research on animal signalling is that signal perception is continuous, or that receivers can perceive and respond to each difference in signal magnitude between signallers. However, although the signal varies continuously across individuals, increasing evidence suggests that not all of that variation is perceived by the receiver, resulting in discontinuous perception. To understand why a signal receiver responds to a signal in a given way, it is crucial to understand how the receiver perceived the signal. Signal perception is a function of the receiver’s sensory physiology and perceptual processes that occur after a signal is transduced by the sensory organ. Currently, however, we know little about how information from the sensory organs is processed in the brain in non-human animals, i.e. how the physical attributes of a signal are linked to behavioural outcomes. This project has investigated perception of size-based traits during mate choice, using the green swordtail fish Xiphophorus helleri. Our primary findings are (1) that visual acuity, the ability to perceive detail, is low in green swordtails, approximately 1/20th that of humans, but is higher in females than males, and that (2) perception of body size, an important mate choice signal in swordtails, is proportional. Under proportional processing, stimuli are compared based on proportional rather than absolute differences in magnitude. Thus, as the overall magnitude of the signal increases, it becomes more difficult for receivers to discriminate differences in size. This project is the first to test for proportional processing of a visual mate choice signal. Understanding how signal receivers perceive signal variation is crucial to understanding how signallers place selection on signal evolution; how receivers evaluate and compare signallers; and ultimately, how the incredible diversity of signalling structures found in the animal kingdom has evolved. Additionally, studying perception in non-human animals can help us understand the diversity of perceptual processing across species, and establish new model systems for cognitive and perceptual studies.
Data: CORDIS, © European Union
Project objective
Individuals evaluate one another during interactions using assessment signals that indicate quality, and these signals vary across individuals, reflecting variation in signaler quality. For example, green swordtail (Xiphophorus helleri) females assess the length of an extended caudal fin (known as a sword) on males, which ranges in length from 10-70mm in nature, during mate choice, and males evaluate one another’s swords during agonistic encounters. Models of signal evolution implicitly assume that signals are perceived continuously, meaning that each change in signal magnitude is both perceived by the receiver and results in a concomitant change in receiver response. Increasing evidence, however, shows that signals across modalities, from acoustic signals to color-based visual signals, can be perceived discontinuously. One mechanism by which stimuli can be perceived discontinuously is called proportional processing, which follows Weber’s law. Under proportional processing, a viewer can more readily discriminate between two stimuli that differ by a certain amount when both of those stimuli are of low magnitude, compared with two stimuli that differ by the same amount but are both high magnitude. Although proportional processing has been shown to operate across a variety of taxa and modalities, no study has yet tested for proportional processing of a visual signal. This project will (1) test whether signal magnitude, i.e. male sword length, is perceived continuously or proportionally by female and male swordtails; (2) assess how perception of stimulus magnitude is affected by variation in environmental conditions, by manipulating both the visual and auditory environment; (3) compare perception of signal-relevant (bars) and signal-irrelevant (circles) stimuli, between a swordtail species that exhibits sexual dimorphism in sword length (X. helleri) with one that does not (X. maculatus), to examine the evolution of perceptual processes; and (4) compare perception of the signal magnitude in swordtails with existing data on length perception in a variety of taxa (including humans), to examine the generality of proportional processing of length across species, and how perception differs between species with very different visual acuities (ability to perceive detail) and signaling behaviours. This project will be the first to examine proportional processing of a visual signaling trait in any non-human animal and will provide the first tests of how viewing conditions and multi-modal stimuli impact perception of signal magnitude in non-primates. By combining my expertise in different mechanisms of discontinuous perception with the expertise of Dr Kelley at Exeter, which spans animal behavior, acoustic signaling, and perceptual processing, we will (1) provide novel insights into the relationship between signal design, behaviour, and environment, (2) increase our understanding of how vision and higher-level perceptual processes interact in the perceptual organisation of stimuli, and (3) provide invaluable training in managing a large project at the forefront of perception research, thus opening a host of career and collaborative opportunities.
Original text from CORDIS.
Participants
- THE UNIVERSITY OF EXETER · ExeterCoordinatorUnited Kingdom
Links
Data: CORDIS, © European Union