The Wertheimer–Benary Effect Does Not Invert, and a Nulled Wertheimer–Benary Effect

Abstract

More than three-quarters of a century ago Wertheimer and Benary demonstrated an ingenious and clear, though, interestingly, small effect: a grey triangle just inside an arm of a black cross on a white background appears slightly lighter than an identical triangle immediately adjacent to the cross, despite both triangles having the same perimeter exposure to black and white. Over a generation ago White discovered an apparently related, but far stronger effect: when short grey (test) bars are placed onto either black or white alternating long bars, the short test bars placed on the long black bars appear much lighter than those placed on the long white bars. A decade ago Spehar, Gilchrist, and Arend found that, enigmatically, if the short test bars in White's effect are the lightest stimulus in a figure, then the relative lightness of the test bars inverts compared with the standard version of White's effect. Here we show that the Wertheimer-Benary effect does not invert, but instead produces a very weak version of the standard effect. We also demonstrate a novel, nulled Wertheimer-Benary effect.