Comparison of Fuzzy Signal Detection and Traditional Signal Detection Theory: Analysis of Duration Discrimination of Brief Light Flashes

Both Traditional and Fuzzy Signal Detection Theory (SDT) methods of analyses were compared using a duration discrimination task of brief light flashes. Both difficulty and response bias (by instruction) were manipulated. The two methods clearly provided different estimates of SDT parameters. The Fuzzy SDT analyses inflated performance while the traditional SDT analyses underestimated performance. In some cases performance on the ‘easier’ condition was worse than on the more ‘difficult’ condition. This may be due to differences in the range of durations discriminated, which was narrower in the ‘easier’ condition. Range of stimuli used can impact performance, although it or maybe an artifact of the procedure for the crisp analysis. Fuzzy SDT met the assumptions of traditional SDT, the assumption of normally distributed noise and signal plus noise distribution holds. In addition, the equal variance assumption holds for the more difficult discrimination for all participants.