In this three-stimulus task the subject is presented with a "triangle"(ABC) of stimuli, two of which are alike, and is asked to locate the "odd" one. This may be any of the three. There are six possible stimulus sequences: (S1, S2, S2) and (S2, S1, S1), for both of which the correct response is "A"; (S2, S1, S2) and (S1, S2, S1), for which the answer is "B"; (S1, S1, S2) and (S2, S2, S1), for which the answer is "C".
- Macmillan, N.A., & Creelman, C.D. 1991. Detection Theory: A User's Guide, New York: Cambridge University Press.