Discrimination of edge orientation by bumblebees

PLoS One. 2022 Jun 16;17(6):e0263198. doi: 10.1371/journal.pone.0263198. eCollection 2022.

Abstract

Simple feature detectors in the visual system, such as edge-detectors, are likely to underlie even the most complex visual processing, so understanding the limits of these systems is crucial for a fuller understanding of visual processing. We investigated the ability of bumblebees (Bombus terrestris) to discriminate between differently angled edges. In a multiple-choice, "meadow-like" scenario, bumblebees successfully discriminated between angled bars with 7° differences, significantly exceeding the previously reported performance of eastern honeybees (Apis cerana, limit: 15°). Neither the rate at which bees learned, nor their final discrimination performance were affected by the angular orientation of the training bars, indicating a uniform performance across the visual field. Previous work has found that, in dual-choice tests, eastern honeybees cannot reliably discriminate between angles with less than 25° difference, suggesting that performance in discrimination tasks is affected by the training regime, and doesn't simply reflect the perceptual limitations of the visual system. We used high resolution LCD monitors to investigate bumblebees' angular resolution in a dual-choice experiment. Bumblebees could still discriminate 7° angle differences under such conditions (exceeding the previously reported limit for Apis mellifera, of 10°, as well as that of A. cerana). Bees eventually reached similar levels of accuracy in the dual-choice experiment as they did under multiple-choice conditions but required longer learning periods. Bumblebees show impressive abilities to discriminate between angled edges, performing better than two previously tested species of honeybee. This high performance may, in turn, support complex visual processing in the bumblebee brain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bees
  • Learning*
  • Visual Fields
  • Visual Perception*

Grants and funding

This study was supported by Human Frontier Science Program grant (RGP0022/2014; www.hfsp.org) to L.C.; Engineering and Physical Sciences Research Council program grant Brains-on-Board (EP/P006094/1; epsrc.ukri.org) to L.C.; European Research Council grant SpaceRadarPollinator (339347; erc.europa.eu) to L.C.; and a Royal Society Wolfson Research Merit Award (royalsociety.org) to L.C. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. There was no additional external funding received for this study.