Signal Detection Theory

What is signal detection theory? (very general)

• psychological theory explaining how people detect stimuli in their environment

What is a signal in SDT?

• refers to the true sensory information coming from external world

What is noise in SDT?

• refers to various physiological and psychological processes influencing our perception of a signal (external stimulus) in an unpredictable manner

  • physiological noise could be spontaneous activity in sensory nerves

  • psychological noise could be spontaneous fluctuations in attention

• noise = whatever is not measured + contributes to variability in participants’ responses

What is sensitivity (d’) in SDT?

• individual's ability to distinguish between signal and noise (regardless of response bias)

• reflets how well they can detect target stimulus

What is the criterion in SDT?

• strength of felt sensation where an individual says yes vs no that they felt stimulus

• determines an individual’s bias

• (intensity required for them to report “yes”)

What is a more conservative bias?

• more likely to withhold detections until certain they perceived

• higher intensity needed to meet detection “criteria”

• may occur when you lose something from false alarms

  • (minimizing false alarms rather than maximizing hits)

What is a more liberal bias?

• more likely to report a detection

• lower intensity needed to meet detection “criteria”

• may occur when you lose something from misses

  • (maximizing hits rather than minimizing false alarms)

What is an ROC curve?

• used to plot the probability of a hit / false alarm

• criterion determines where points are on curve

• sensitivity impacts shape of curve