Chapter 2: Signal Detection and Absolute Judgement

Slide Template

SIGNAL DETECTION THEORY

The Signal Detection Paradigm

• Hit, misses, false alarms and correct rejections.

The Signal Detection Paradigm

• Change in the evidence variable caused by a weak and strong signal.

The Signal Detection Paradigm

• Hypothetical distribution underlying signal detection theory and sensitivity

Setting the Response Criterion: Optimally in SDT

• Signal probability. Optimal beta.• Payoffs. Expected value.

Setting the Response Criterion: Optimally in SDT

• Human Performance in Setting Beta.• Sluggish beta. • Relationship between obtained and optimal

decision criteria.

Sensitivity

• Misses result because of high beta or low sensitivity

THE ROC CURVE

Theoretical Representation

• Receiver Operating Characteristic (ROC) curve

Theoretical Representation

• Analysis of confidence ratings in signal detection tasks.

Theoretical Representation

• Z-scores.

Empirical Data

• Distinction between theoretical data and actual empirical data collected in an experiment

FUZZY SIGNAL DETECTION THEORY

Fuzzy SDT

• Combining SDT and fuzzy logic.• Mapping function.

APPLICATIONS OF SDT

Medical Diagnosis

• Disease prevalence.

Recognition Memory and Eyewitness Testimony

• Relative judgment

Alarm and Alert Systems

• SDT and warning signals

Alarm and Alert Systems

• Alarm false alarms– Minimum safe altitude warning

• Solutions: – Use multiple alarm levels– Raise automated beta slightly– Keep the human in the loop– Improve operator understanding of alarm false

alarms.

VIGILANCE

Target versus non-target events

• Vigilance level and vigilance decrement

Measuring Vigilance Performance

• Influences on sensitivity• Changes in bias

Theories of Vigilance

• Arousal theory

Theories of Vigilance

• Sustained demand theory.• Expectancy theory.

Techniques to Combat the Loss of Vigilance

• Increasing sensitivity: – show target examples– increase target salience– reduce the event rate– train observers

• Shift in Response Criterion. – Instructions, knowledge of results, false signals,

confidence levels• Other techniques– Arousal and fatigue

Application

• Inside and outside the Laboratory• Examples– Situation Awareness

ABSOLUTE JUDGMENT

Quantifying Information

• Bits

Single Dimensions

• Experimental Results• Channel capacity• Bow Effect• Applictions

Multi-dimensional Judgment

• Orthogonal Dimensions

Multi-dimensional Judgment

• Correlated Dimensions

Multi-dimensional Judgment

• Dimensional Relations: – Integral and Separable. – Garner Sort task.

Multi-dimensional Judgment

• Configural Dimensions– Emergent features.

• Summary

Multi-dimensional Judgment

• Implications of Multi-Dimensional Absolute Judgment– Example of configural dimensions for the heights

and widths of rectangles