Comparison of Algorithms to Measure a Psychophysical Threshold using Digital Applications: The Stereoacuity Case Study

The use of digital applications to perform psychophysical measurements led to the introduction of algorithms to guide the users in test execution. In this paper we show three algorithms, two already well known: StrictStaircase and PEST, and a new one that we propose: PEST3. All the algorithms aim at estimating the level of a psychophysical capability by performing a sequence of simple tests; starting from initial level N, the test is executed until the target level is reached. They differ in the choice of the next steps in the sequences and the stopping condition. We have applied the algorithms to the stereoacuity case study and we have compared them by answering a set of research questions. Finally, we provide guidelines to choose the best algorithm based on the test goal. We found that while StrictStaircase provides optimal results, it requires the largest number of steps and this may hinder its use; PEST3 can overcome these limits without compromising the final results.