Decision strategies for the two-alternative forced choice reminder paradigm.

The decision strategy adopted by an observer in a psychophysical procedure may be established by comparing estimates of sensitivity obtained by using detection-theoretic models based on each of the available decision strategies. Estimates of sensitivity obtained from 10 observers on auditory-level discrimination tasks using the yes/no, two-alternative forced choice (2AFC), and 2AFC with reminder (2AFCR; sometimes called duo-trio) procedures were compared in order to determine the decision strategy used by the judges in the 2AFCR procedure. 2AFCR permits at least three decision strategies: differencing, likelihood ratio, and comparison of distances. The latter strategy has frequently been assumed in the analysis of duo-trio data in the sensory evaluation literature. The present study demonstrates that the comparison-of-distances strategy was not used by 9 of the 10 observers in this auditory experiment. The nature of the instructions given to the observers had no measurable impact on the decision strategy that they adopted.