Method of Adjustment
2 tokens / session
Participants drag a stimulus until it perceptually matches a reference. Continuous DV captures illusion magnitude or perceptual thresholds.
Choose this if
you run Müller-Lyer, Ebbinghaus, Ponzo, vertical-horizontal or any classical illusion where magnitude is the outcome.
Results look like
mean adjustment error per condition with 95% CIs – »Müller-Lyer illusion magnitude: 18.4 px (SD 6.1)«.
Try it yourself
You'll see two horizontal lines with arrowheads. One is a fixed reference; the other is adjustable. Drag the slider until they look the same length.
Starter templates
Müller-Lyer illusion — starter
Adjust the variable line until perceived equal to the reference. Illusion magnitude = adjustable − reference (in px).
Ebbinghaus illusion — starter
Central circle with small vs large satellites. Adjust the right-side circle to match perceived size.
Ponzo illusion — starter
Two converging depth lines; adjust the “far” line to match the “near” one.
Vertical-horizontal illusion — starter
Adjust the horizontal line to match the vertical reference.