Page 1 of 1 PSY3002_Cognitive Lab © 2009 South University
The Signal Detection Experiment In the signal detection experiment, you watch a random display of dots and see if you can detect a diagonal line of dots. At the end of the experiment, instead of just reporting the percentage of correct responses, the numbers of hits, false alarms, misses, and correct rejections are provided.
• Hit: A hit is reporting a line when a line is present.
• False Alarm: A false alarm is reporting a line when no line is actually present.
• Miss: A miss is not reporting a line when a line is present.
• Correct Rejection: A correct rejection is not reporting a line when no line is present.
These measures reflect sensitivity and consider response bias. For example, a person who reported yes on every single trial would have lower sensitivity than someone who had a mix of hits and correct rejections. The measure of sensitivity in SDT is called d’ (d prime), and the measure of response bias is called β (beta). These values are calculated from proportions of hits and false alarms.
Signal Detected a Signal Did Not Detect a Signal
Present (Correct) Hit Miss
Absent (Incorrect) False Alarm Correct Rejection