Chapter 8 Sensation & Perception

Sensation & Perception What occurs when a stimulus activates a receptor. Perception The organization of sensory information into meaningful experiences.

Psychophysics The study of the relationships between sensory experiences and the physical stimuli that caused them.

Thresholds Absolute threshold Difference threshold The weakest amount of a stimulus that a person can detect half the time. Difference threshold The smallest change in a physical stimulus that can be detected between two stimuli. Also known as the JND

Approximate absolute thresholds for the 5 senses: Vision - Candle flame seen at 30 miles on a clear, dark night. Hearing - Tick of a watch under quiet conditions at 20 feet. Taste - 1 Teaspoon of sugar in 2 gallons of water. Smell - 1 Drop of perfume diffused into a three-room apartment. Touch - A bee's wing falling on your cheek from 1 centimeter above.

Weber’s Law For any change in a stimulus to be detected, a constant proportion of that stimulus must be added or subtracted.

Sensory Adaptation Your senses are most responsive to increases and decreases, and to new events rather than to ongoing, unchanging stimulation.

Detecting Stimuli Signal-detection theory The study of people’s tendencies to make correct judgments in detecting the presence of stimuli.

The Stroop Effect

Stare at the grid only briefly, and you will see areas of gray at the intersections of the white rows and columns.

Now, try to count the black dots in this one.