Sensation and Perception

Chapters 5 & 6

Some Basic Questions

How do we sense the world?

Some Basic Questions

How do we sense the world? How do we perceive color?

Some Basic Questions

How do we sense the world? How do we perceive color? How do we perceive motion?

Some Basic Questions

How do we sense the world? How do we perceive color? How do we perceive motion? How do we perceive size and shape?

Some Basic Principles

Sensation Detecting physical energy from the environment and

encoding it as neural signals

Perception Select, organize, and interpret our sensations How our mind interprets what our senses detect

Sensation and Perception do not always cooperate

Sensation Bottom-Up Processing

analysis that begins with the sense receptors and works up to the brain’s integration of sensory information

Top-Down Processing information processing guided by higher-level

mental processes as when we construct perceptions drawing on

our experience and expectations

Sensation Our

sensory and perceptual processes work together to help us sort out complext processes

Sensation- Thresholds

Absolute Threshold minimum stimulation needed to detect a

particular stimulus 50% of the time Difference Threshold

minimum difference between two stimuli required for detection 50% of the time

just noticeable difference (JND)

Difference Threshold

Weber’s Law- to perceive as different, two stimuli must

differ by a constant minimum percentage light intensity- 8% weight- 2% tone frequency- 0.3%

Are these two colors the same?

Are these two colors the same?

Are these two colors the same?

Are these two colors the same?

Are these two colors the same?

Sensation- Thresholds

Subliminal When stimuli are

below one’s absolute threshold for conscious awareness

0

25

50

75

100

Low Absolutethreshold

Medium

Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

Subliminal Advertising

Subliminal Messages

Do subliminal messages work in songs?

Lets find out!

Sensation- Thresholds 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

Can you spot the “C”

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOCOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

Can you spot the “N”

MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMNMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM

Can you spot the “R”?

BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBB

Sensory adaptation- diminished sensitivity as a consequence of

constant stimulation