Sensation and Perception

1. Sensation and Perception Sensation: your window to the world Perception: interpreting what comes in your window.

2. Sensation • the passive process of bringing information from the outside world to the body and the brain • Process of sensing our environment through taste, sight sound, touch and smell • Example:

3. Perception • the active process of selecting, organizing, and interpreting the information brought to the brain by the senses • Perception is the way we interpret sensations and therefore make sense of everything around us • Example:

4. Bottoms-up Processing • AKA - Feature analysis • Begins with the sensory receptors and works its way up to the brain • Use the features of the object itself to process the information • Examples:

5. Top Down Processing • Processing information from the senses with higher level mental processes using our experiences and expectations • Using your background knowledge to fill in the gaps • Example:

6. Selective Attention • Ability to focus our conscious awareness on a particular stimulus • Example:

7. Selective Attention

8. Cocktail-party phenomenon • The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations. • Form of selective attention. • Example:

9. Selective Inattention • Change Blindness/Inattentional Blindness - Falling to notice changes in the environment • Example: • Choice Blindness - failure to notice a switch in a choice that is made • Example: • Change deafness – failure to notice a change in voices that are speaking • Example: • Pop out – stimuli we don’t chose to attend to but they draw our eyes and demand our attention • Example:

10. Psychometrics • Study of howphysical stimuli are translated into psychological experience. • Psychologists use thresholds to measure these events • Example:

11. Thresholds • Absolute threshold – minimum stimulation needed to detect a stimulus of light, sound pressure, taste, or odor 50% of the time • Examples:

12. Signal Detection Theory • Predicts how and when we detect a signal amid background noise • Assumes no absolute threshold • Detection depends partly on a person’s experience, expectations , motivation and alertness… alertness…people respond differently to same stimuli • Examples:

13. Subliminal Stimulation • Subliminal Stimulation – below one’s absolute threshold for conscious awareness • Example • Priming – increased sensitivity to certain stimuli due to prior experience outside conscious awareness • Example

14. 100 75 Percentage of correct detections 50 Subliminal stimuli 25 0 Low Medium Absolute threshold Intensity of stimulus Do Subliminal Messages work? • Based on studies, some people do respond to stimuli below the absolute threshold, under some circumstances. • The problem is people behave differently at different levels, so what could be subliminal (or below the threshold) for one person, may be supraliminal (above the threshold) for another person.

15. Backmasking- More Subliminal Messaging?Listing to Songs in Reverse • There are legends about hidden messages in songs - Led Zeppelin's Stairway to Heaven was one of the first songs to have supposed hidden, satanic messages. • http://jeffmilner.com/backmasking.htm • Why does this seem to work?

16. Difference Threshold AKA • Just Noticeable Difference – the amount a change needed in a stimulus (stronger or weaker) for us to recognize the change has occurred • the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change. • Example:

17. Weber’s Law • Related to JND • For people to really perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount". • Proportion varies depending on the stimulus • Example:

18. Weber’s Law • JND = Constant (K) X Intensity • Pitch = .003 ( if someone sings a little off key, we will be able to tell) • Loudness = .10 • Saltiness = .20 • Light = .08 • Example:

19. Sensory Adaptation • Diminished sensitivity as a consequence of constant stimulation • Example Do you feel your underwear all day?