Module 11

Introduction to Sensation and

Perception

Sensation

Sensation the process by which our sensory

receptors and nervous system receive and represent stimulus energy

Perception the process of organizing and

interpreting sensory information, enabling us to recognize meaningful objects and events

Sensation

Sensationhow do we change energy into sense

Perceptionwhat do we do with our sensory information

Sensation Our

sensory and perceptual processes work together to help us sort out complex images

Sensation

Bottom-Up Processing analysis that begins with the sense

receptors and works up to the brain’s integration of sensory information (piecing lines together to recognize the number 4)

Top-Down Processing information processing guided by

higher-level mental processes as when we construct perceptions

drawing on our experience and expectations (think you know someone and as they get closer, realize that you don’t)

Sensation- Basic Principles

Psychophysics study of the relationship between

physical characteristics of stimuli and our psychological experience of them

Light- brightness Sound- volume Pressure- weight Taste- sweetness

Sensation- Thresholds Absolute Threshold

minimum stimulation needed to detect a particular stimulus 50% of the time

isn’t constant – can change with motivation and alertness

Difference Threshold minimum difference between two stimuli

required for detection 50% of the time just noticeable difference (JND)

Sensation- A. 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

Sensation- A. Thresholds

Signal Detection Theorydetection of stimuli involves decision processes as well as sensory processes

Example – riddle, shower/telephone

“You’re driving a bus with 12 passengers. At your first stop, 6 passengers get off. At the second stop, 3 get off. At the third stop, 2 more get off, but 3 new people get on. What color are the driver’s eyes?

Did you detect the signal – who is the driver? – over the noise – number of passengers?

Sensation- A. 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

Sensation- A. Thresholds

Subliminal Messages

Reverse Speech - Voices From The Unconscious

Sensation- Thresholds

Difference Threshold minimum difference between two

stimuli required for detection 50% of the time

just noticeable difference (JND) – we experience the difference threshold as a JND.

Read the passage at the right.

How many lines do you require to experience a noticeable difference?

Sensation- D. Thresholds

Weber’s Law to be perceived as different, two

stimuli must differ by a constant minimum percentage (rather than a constant amount) light intensity- 8% (1/60) weight- 2% (1/50) tone frequency- 0.3% (1/333)

Sensation- D. Thresholds

Sensory Adaptation diminished sensitivity as a

consequence of constant stimulation(wearing a new wristwatch)

Selective Attention focusing of conscious awareness

on a particular stimulus as in the cocktail party effect

(listen to one voice, among many)

Now you see it, now you don’t!

Perception

Selective Attention

Do you see circles with white lines or a cube?

Because attention is selective, you only see one interpretation at a time.

Change Blindness

Change Blindness is an example of Selective Attention

Lab Demos

Change Blindness