El Greco fallacy

It is believed the term originated with Irvin Rock, in his 1966 book, The Nature of Perceptual Adaptation.

[3] Chaz Firestone and Brian Scholl have alleged that this fallacy has been the cause for mistaken thinking in perception research,[1][4] including in studies that presumed to show that wearing a heavy backpack makes hills literally appear steeper, or holding rods outstretched horizontally would make doorways look narrower.

In the example of holding rods outstretched, the original experiment had subjects evaluate the width of apertures (intended to simulate doorways), then show this width on a ruler held by experimenters.

[5] When Firestone and Scholl repeated this experiment, substituting rulers for a separate aperture that was adjusted by experimenters to the subjects instruction, the aperture was still evaluated as narrower.

This narrowing effect was later implied to be a demand characteristic after another group was told that their holding a rod was an evaluation of balance abilities.