Eight ways to ask people how similar things are
A tutorial review in Attention, Perception, & Psychophysics surveys the common methods for collecting similarity judgments. Each one is runnable below. Try a short version yourself, or let a simulated participant answer, and see the similarity matrix and 2-D MDS map the method produces.
Daggett, E. W., & Hout, M. C. (2025). A tutorial review on methods for collecting similarity judgments from human observers. Attention, Perception, & Psychophysics, 87, 737–751. doi:10.3758/s13414-025-03044-3
Ratings reproduced from Table 1 of the paper. The authors describe them as loose relative guidelines, some not yet validated experimentally. “Reliability” means likely consistency between participants; “Geometric” methods force symmetric proximities.
The simulated participant answers from a hand-coded feature list for each stimulus (for animals: mammal, four legs, flies, canine, domestic, size, hooves, scales; for shapes: hue and number of sides) plus random noise. It exists to show what each method's output looks like, not to model real observers.