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 Visual 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

Low Absolute threshold Medium Intensity of stimulus Percentage of correct detections 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