Effects of specificity of probability information on human performance in a signal detection task

Abstract

The effects of specificity of probability information on human performance were investigated in two experiments differing only in task difficulty. Subjects decided whether a stimulus was a ‘friend’ or ‘foe’. Four signal detection-aids presented the probability of a ‘foe’ according to differing levels of specificity: (a) two-categories, (b) four-categories, (c) six-categories, and (d) eight-categories. In the fifth condition, the control, no signal detection-aid was present. Hick's law applied to the unsure and correct response times for the four (2·0 bit), six (2·5 bit), and eight (3·0 bit) category aids for both experiments. An inverted U-shaped function was hypothesized for sensitivity (d _a) as a function of aid specificity. In the easier task the eight-category aid and the two-category aid group sensitivity was not significantly different from the other aids. However, the eight-category aid group had greater confidence than the other groups. For the harder task there was no reduced sensitivity for subjects using the eight-category aid, but the two-category aid had reduced sensitivity. In both experiments the mean criteria (B′) for the aided conditions were too liberal when the aid indicated a low probability (M = 0·2) for a ‘foe’.

Now at User Systems Engineering, Texas Instruments, PO Box 655474, M/S 238, Dallas, TX 75265, USA.

Keywords:

• Automation
• Decision-aiding
• Probability
• Response time
• Uncertainty

Notes

Now at User Systems Engineering, Texas Instruments, PO Box 655474, M/S 238, Dallas, TX 75265, USA.