• The language of the eyes

    From ScienceDaily@1:317/3 to All on Tue Mar 8 21:30:38 2022
    The language of the eyes
    Relevance of the human white of the eye for communication

    Date:
    March 8, 2022
    Source:
    University of Konstanz
    Summary:
    What is the significance of the sclera of our eyes? A question which
    researchers have been interested in for some time now. Recently
    a research team led by a comparative psychologist has succeeded
    in deciphering the mystery: The white of the eye contributes
    decisively to the visibility of directions of gaze through its
    basic color properties.



    FULL STORY ==========================================================================
    What is the significance of the sclera of our eyes? A question which researchers have been interested in for some time now. Recently a research
    team led by a comparative psychologist has succeeded in deciphering the mystery: The white of the eye contributes decisively to the visibility
    of directions of gaze through its basic color properties.


    ==========================================================================
    When we talk to other people, we usually maintain eye contact with
    one another.

    We know exactly who is looking at whom and which unspoken messages
    the person is displaying using the "language of their eyes" or which
    object they are looking at. Whilst communicating this helps us humans
    to be able to identify the direction of the other person's gaze
    quickly and clearly. "We owe this to the formation of the whites of
    the eye. Humans might have evolved this distinguishing eye feature for conspecific communication," says Kano. "In doing so, humans have probably evolved a unique communicative style critical for their hallmark social activities." Kano is a junior group leader at the Centre for the Advanced
    Study of Collective Behaviour (CASCB), a cluster of excellence at the University of Konstanz. This study goes back to research he conducted
    with Yuri Kawaguchi and Hanling Yeow at Kumamoto Sanctuary at the Kyoto University.

    Humans and chimpanzees can perceive the human eye better than the
    chimpanzees eye But how did the researchers reach these groundbreaking findings? The results are based on experiments Kano's research team
    conducted with humans and chimpanzees -- the closest relatives of
    humans. Both study groups were presented with images of humans and
    chimpanzees in computerized tasks. During the experiment, the task was
    to distinguish the gaze directions of humans and chimpanzees. Over a
    period of several months, the chimpanzees were presented with pictures of different perspectives of eyes of both species -- two with a straight
    line of eye sight, one viewing to the side. If they pointed to the
    picture with the shifted eye, they received a reward. Kano explains:
    "We found that both humans and chimpanzees distinguished eye-gaze
    directions of humans better than those of chimpanzees, particularly in
    visually challenging conditions." The researchers also observed that participants of both species distinguished the eye-gaze directions of chimpanzees better when the contrast polarity of the chimpanzee eye was reversed compared to when it was normal; namely when the chimpanzee
    eye had human-like white sclera and a darker iris. Whiteness in the
    sclera thus facilitates the visibility of eye-gaze direction even across species. "Our findings thus support but also critically update the central premises of the gaze-signalling hypothesis," summarizes Kano his findings.

    The novel aspect of the study is that the three researchers chose a cross- species design for comparison for the first time. In the experiments,
    they presented eye images to both chimpanzee and human participants. This
    is essential for distinguishing between several alternative hypotheses,
    Kano informs us.

    Video: https://youtu.be/MM_yiM3-Vhw

    ========================================================================== Story Source: Materials provided by University_of_Konstanz. Original
    written by Dr Elisabeth Bo"ker. Note: Content may be edited for style
    and length.


    ========================================================================== Journal Reference:
    1. Fumihiro Kano, Yuri Kawaguchi, Yeow Hanling. Experimental evidence
    that
    uniformly white sclera enhances the visibility of eye-gaze direction
    in humans and chimpanzees. eLife, 2022; 11 DOI: 10.7554/eLife.74086 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220308102743.htm

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