Outline- and solid-angle orientation illusions have different determinants

Peter Wenderoth*, Tony O'Connor

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    11 Citations (Scopus)


    Six experiments together suggest that negative illusions (assimilation effects) induced by either single solid acute-angle or double solid-angle (Bourdon) displays are explained by a failure to discriminate the judged edge of the angle(s) from the other edge and from the average orientation of the display [the bisector(s) of the angle figure]. The evidence for this is that Bourdon effects occur only when the judged edge is straight (Experiments 1 and 2) and only when the edge is not vertical or horizontal (Experiments 1, 3, and 4), and that these effects are enhanced by manipulations that reduce acuity for parallelism (Experiments 5 and 6). None of these variables affect outline-angle tilt illusions in the same fashion, which strongly suggests that solid- and outline-angle illusions have entirely different determinants.

    Original languageEnglish
    Pages (from-to)45-52
    Number of pages8
    JournalPerception and Psychophysics
    Issue number1
    Publication statusPublished - Jan 1987


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