1. Sensation and Perception
Sensory input and Psychophysics

2. Sensation and Perception
What do you hear?
What do you see?
What do you taste?
What do you smell?
What do you feel? (not emotion)
What conclusions can you draw from these answers?

3. Sensation
Starts with a stimulus (any aspect of change in our environment to which we respond)
Can be measured in size, duration, intensity and wavelength
Occurs anytime a stimulus activates a receptor

4. Sensory Receptor Living cell that responds to certain type of energy
Often located in sense organs
Specialized structure that collects energy particularly well… (eye, ear, etc)
Detect physical changes in energy such as heat, light, sound, and physical pressure

5. Eye- notes changes in light

6. Ear- notes changes in sound

7. Skin- notes changes in heat and pressure

8. Perception
Organization of sensory information into a meaningful experience
Comes from a combination of sensations and past experiences

9. Psychophysics
The interaction between the physical world (stimuli) and the psychological world (internal experience)
What is the relationship between color and wavelength?
How does changing a light’s intensity affect your perception of it’s brightness?

11. Threshold
How much energy is required for someone to hear a sound, or see a light?
How much of a scent must be in a room for someone to smell it?
How much pressure must be put on the skin for someone to feel it?
Is it the same for everyone?

12. How strong must a stimulus be in order for detection?
Threshold- dividing line
Not exact
Absolute threshold- point at which a very weak stimulus can be detected 50% of the time
Difference threshold- smallest change a person can detect 50% of the time.
(JND) just noticeable difference

13. Weber’s Law
The larger the magnitude of the stimulus, the larger the JND
25 watt light bulb / 50 watt light bulb very different
175 watt light bulb / 200 watt light bulb hard to notice

14. Weber’s Law
The JND increases in direct proportion to the intensity of the stimulus.
Often not true when stimuli approach extreme values.

15. Fechner’s Law Accounts for the extreme values exception
Can be demonstrated in a curve
Follows a logarithmic relationship
The curve drops as the magnitude of the stimulus approaches extreme values

16. Fechner’s Law
Exceptions include electric shock and heaviness

17. Sensory adaptation
Our senses are tuned to change and respond to increases and decreases in stimuli, or new events rather than constant stimulation.
We adapt to change/deviation in stimulation
Movie theater
Clothes on body

18. Signal Detection theory
Study of people’s tendencies to make correct judgments in detecting the presence of stimuli
Recognizing stimuli against a competing background of stimuli
Individuals vary based on situation
Preattentive process-getting info automatically when presented
Attentive process- paying attention to only one of the stimuli at a time when presented with multiple stimuli p 213

19. Look at page 210