PSYC 101 Lecture Notes - Detection Theory, False Alarm, Sensory Threshold

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6 Apr 2012
Sensation and Perception
Sensation: process in which the stimulation of receptor cells sends nerve impulses to the brain.
Perception: process in which the brain interprets sensations, giving them order and meaning.
Stimulus Discrimination:
Just Noticeable Difference (JND) (minimum difference accurately perceived). Sitting in a
dark room…having two lights shone from different doors and asked which light is
Weber’s Law (JND in sensation is always a constant proportion of the initial intensity).
For lighter things, we can spot smaller differences. For heavier things, we don’t really
notice small changes (1g in a 1kg object…hard to notice).
Fechner’s Law (as intensity increases, larger increases are needed to produce
subjectively equal changes)
Stimulus Detection:
Sensory threshold. When can you first detect a sound? When can you first detect a
light? Etc.
Signal detection theory
Hit (saying yes when the event did occur), miss (saying no when event occurred), correct
rejection (saying no when the event does not occur), false alarm (saying yes when the
event didn’t occur)
Percentage of hits and false alarms depends on the criterion. If you’re being rewarded for the
hits, you’ll be a lot more careful in not making a mistake - High chance of hits and vice-versa.
Clicker: Which of the following qualifies as a miss? Answer: A signal is present and the
participant says “no”.
Clicker: While jenny is in the shower she is listening for the phone because she is
expecting an important call about a new job. She is more likely to make a _________
than a _______. Answer: False alarm; miss.
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