# The effects of non-diagnostic information on confidence and decision making

## TL;DR

This study explores how non-diagnostic information affects confidence and decision-making in perceptual tasks.

## Contribution

The paper empirically validates the doubt-scaling model's predictions about non-diagnostic information's impact on confidence and accuracy.

## Key findings

- Increasing non-diagnostic information reduced confidence and accuracy in perceptual tasks.
- Non-diagnostic information generally slowed response times and increased error speed.
- Results were replicated in a decision-only task, supporting the doubt-scaling model.

## Abstract

Many decision-making tasks are characterized by a combination of diagnostic and non-diagnostic information, yet models of responding and confidence almost exclusively focus on the contribution of diagnostic information (e.g., evidence associated with stimulus discriminability), largely ignoring the contribution of non-diagnostic information. An exception is Baranski and Petrusic’s Journal of Experimental Psychology: Human Perception and Performance, 24(3), 929-945, (1998) doubt-scaling model, which predicts a negative relationship between non-diagnostic information and confidence, and between non-diagnostic information and accuracy. In two perceptual-choice tasks, we tested the effects of manipulating non-diagnostic information on confidence, accuracy and response time (RT). In Experiment 1, participants viewed a dynamic grid consisting of flashing blue, orange and white pixels and indicated whether the stimulus was predominantly blue or orange (using a response scale ranging from low-confidence blue to high-confidence orange), with the white pixels constituting non-diagnostic information. Increasing non-diagnostic information reduced both confidence and accuracy, generally slowed RTs, and led to an increase in the speed of errors. Experiment 2 replicated these results for a decision-only task, providing further support for the doubt-scaling model of confidence.