DOI:10.6129/CJP.202206_64(2).0005
Chinese Journal of Psychology 2022, Vol.64, No.2, 217-232

Incorporating Response Confidence into Adaptive Methods for Threshold Estimation

Che Cheng(Department of Psychology, National Taiwan University), Yan-Jun Huang(Department of Psychology, National Taiwan University), Yung-Fong Hsu(Department of Psychology, National Taiwan University; Graduate Institute of Brain and Mind Sciences, National Taiwan University; Neurobiology and Cognitive Science Center, National Taiwan University)

Abstract

In psychophysical studies of discrimination, thresholds are commonly estimated by (nonparametric, fixed-step- size) adaptive methods using a binary response format. However, it can sometimes be challenging for participants to give a dichotomous response. To resolve the issue, scholars have suggested adding more response categories to the algorithm (Kaernbach, 2001; Klein, 2001). However, Hsu and Chin (2014) argued that their extension has some limitations. Following Hsu and Chin (2014), we proposed an alternative framework to incorporate response confidence into existing adaptive methods for Yes/No tasks. In particular, we introduced the concept of a “cut-off,” thereby expanding the meaning of psychometric functions to psychometric surfaces. We performed simulations to investigate the feasibility of the framework. We considered three adaptive methods, namely Derman’s Up-Down (DUD) method (Derman, 1957), the Biased Coin Design (BCD) (Durham & Flournoy, 1995), and the Weighted Up-Down (WUD) method (Kaernbach, 1991). Setting 0.75 as the target probability for the threshold, we systematically manipulated the initial value, step size, cut-off, and number of trials to examine their impact on the threshold estimation performance of the three adaptive methods. Our simulation results showed that the proposed framework is applicable in general and that WUD and BCD performed slightly better than DUD. We also extended the framework to the Same/Different task, where the psychometric function is not monotonically increasing. We tackled this issue by providing mappings between the response confidence scales of the Same/Different task and the Yes/No task. Doing this enables us to obtain a transformed psychometric function that satisfies the monotonicity property, and thus the aforementioned framework can be readily applied to the Same/Different task.

Keywords: response confidence, adaptive methods, threshold estimation