title: The effect of orientation on the clarity of Hermann grid illusory lines.
abstract: To test the hypothesis that Hermann grid illusory lines are most clear when the grid is presented at a 45 deg, each of 20 participants underwent 10 trials in each of two conditions ('make the lines least clear' and 'make the lines most clear') which were run using a method of adjustment. A matched-pairs t-test applied to the means of the two conditions was significant beyond the 0.01 level. One-group t-tests supported the claim that the illusory lines are least clear for a vertical/horizontal orientation of the grid and most clear when it is rotated 45 deg. The results substantiate, in a systematic manner, 70 years of claims about the effects of grid orientation on illusory line clarity.
authors.affiliation: The University College of the Cariboo, Kamloops, BC, Canada. dgoldwaithe@cariboo.bc.ca
authors.forename: D
authors.initials: D
authors.lastname: Goldthwaite
authors.forename: A
authors.initials: A
authors.lastname: Crowther
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D012016:Reference Values