Sensation & Perception

ATTENTION, PROCESSING, THRESHOLDS

• Goals Contrast sensation & perception; understand how we process & attend to stimuli in the environment.

Sensation

• Process by which our sensory receptors and nervous system receive and represent stimulus energy

Perception• Process of organizing & interpreting

sensory information, enabling us to recognize meaningful objects and events

Bottom-up Processing• Analyze stimulus beginning w/sensory

receptors and work up to brain’s integration of sensory info

Sensory cortex

Auditory cortex

Top-down Processing• Process info by higher-level mental

processes• Draw upon experiences &

expectations

Selective Attention: Focusing conscious awareness• “Cocktail party affect” – attending to

one sound/voice in an environment • Inattentional blindness – missing stimuli

in environment due to selective attention

• Change blindness – missing changes in stimuli due to selective attention

• Goal Distinguish between absolute thresholds and difference thresholds.

What is the absolute threshold?• Weakest amount of a stimulus

that a person can detect 50% of the time

Signal Detection Theory • Predicts how and when we detect the

presence of a faint stimulus (signal) amid background stimulation (noise)

Assumes that there is no single absolute threshold

Detection depends partly on person’s experience expectations motivation level of fatigue

Subliminal Perception• Below one’s absolute threshold for

conscious awareness• Priming will activate

your conscious mind, predisposing one’s perception, memory, or response

0

25

50

75

100

LowAbsolutethreshold

Medium

Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

What is the difference threshold?• Minimal difference or change in

intensity of a stimulus that a person can notice 50% of the time– i.e. Change in volume on the radio,

change in lighting

Sensory Adaptation• Decreased sensation

due to constant stimulation.

• Decreased sensitivity to stimulus