1. 1 HOW do we Sense Things? SENSE RECEPTORS are cells located in the sense organs (eyes, ears, etc.) that convert _______________ energy to ______________ energy SENSE RECEPTORS ▼ SENSORY NEURONS ▼ BRAIN CELLS I’m not the only one who has electrical currents running through my body!

2. 2 Your brain interprets info. in 2 different ways 1) _____________________ your sense organs (eyes, ears, nose, etc.) send impulses along designated nerve pathways to specific parts of the brain. ► Tells the various senses apart! EXAMPLE: Eye info. goes to the visual cortex

3. 3 2) _____________________ rely on the fact that sensory neurons fire, or are inhibited from firing, only when presented with specific stimuli. ► Tells the difference between sensations WITHIN a particular sense! EXAMPLE: Color vs. Shape

4. 4 What do you think might happen if your sensory neurons sent information to the wrong part of the brain?

5. 5 WEIRD, but TRUE! _______________: A rare condition in which stimulation of one sense also evokes a sensation in another In other words, a person might see sounds or smell colors EXAMPLE 1: A person may say that the aroma of cinnamon feels like velvet EXAMPLE 2: One might say that the sound of a clarinet tastes like cherries.

6. 6 Sensing the World: Some Basic Principles  Threshold  Absolute Threshold  Difference Threshold  Subliminal Stimulation  Signal Detection Theory  Sensory Adaptation

7. 7 THRESHOLDS 1)________________________: The smallest quantity of physical energy that can be reliably detected by an observer RELIABLE = Detection _____ of the time EXAMPLE: What’s the smallest line you will read correctly 50% of the time?

8. 8

9. 9 No Detection Intensity Absolute Threshold Detected Yes No Observer’s Response Tell when you (the observer) detect the light.

10. 10 Thresholds Absolute Threshold: Minimum stimulation needed to detect one particular stimulus 50% of the time. Proportion of “Yes” Responses 0.00 0.50 1.00 0 5 10 15 20 25 Stimulus Intensity (lumens)

11. 11 NORMAL SENSORY ABILITIES VISION: A candle flame on a clear, dark night from _____ miles away. HEARING: A ticking watch in perfectly quiet room from _____ feet away TASTE: A teaspoon of sugar diluted in _____ gallons of water SMELL: A drop of perfume diffused through a ____-room apartment TOUCH: Feel the wing of a bee falling in your cheek from a height of ______

12. 12 THRESHOLDS 2) _________________________: The smallest difference in stimulation that can be reliably detected when comparing two things A.K.A. Just Noticeable Difference

13. 13 Difference Threshold Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold Tell when you (observer) detect a difference in the light. No Observer’s Response NoYes

14. 14 Weber’s Law Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. StimulusConstant % Light8% Weight2% Tone.3%

15. 15 DIFFERENCE THRESHOLD When comparing 2 objects, A and B, the difference threshold will depend on the intensity or size of A. –The larger or more intense A is, the greater the change must be before you can detect a difference.

16. 16 DIFFERENCE THRESHOLD EXAMPLE In comparing 2 pebbles, you might be able to detect a difference of only a fraction of an ounce In comparing 2 massive boulders, such a subtle difference would most likely not be noticed.

17. 17 How did Scientists figure this out?......Psychophysics A study of the relationship between physical characteristics of stimuli and our psychological experience with them. Physical World Psychological World LightBrightness SoundVolume PressureWeight SugarSweet

18. 18 Signal Detection Theory (SDT): highlights the limitations of measuring absolute and difference thresholds Signal Detection Theory (SDT): Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Person’s experience Expectations Motivation Level of fatigue Carol Lee/ Tony Stone Images ___________________: some people are habitual yea-sayers and others are habitual naysayers which can greatly affect and disrupt data collection techniques.

19. 19 SDT Matrix Decision YesNo Signal Present Hit Miss or False Negative Absent False Alarm or False Positive Correct Rejection The observer decides whether she hears the tone or not, based on the signal being present or not. This translates into four outcomes.

20. 20 Subliminal Threshold Subliminal Threshold: When stimuli are below one’s absolute threshold for conscious awareness.

21. 21 SUBLIMINAL ORIGINS 1950s Movie theater owner claimed to sell more refreshments when he flashed the words “EAT MORE POPCORN” or “DRINK COKE” for a split second on the screen. Turned out to be a hoax

22. 22 SUBLIMINAL MESSAGES Subliminal messages have appeared in all kinds of places: –Magazines –Movies –Political Campaigns –Weight Loss Strategies –Self-Improvement Books –Memory Enhancers and Study Aids

23. 23 SELF-HELP SUBLIMINAL TAPES Many promise to help you stop smoking, lose weight, relieve stress, or stop taking drugs Study = Placebo tapes vs. “Real Tapes”

24. 24 The Effect of Subliminal Stimuli “Absolute” threshold is merely the point at which we detect a stimulus half the time. Therefore it is possible to sense subliminal (below threshold) stimuli. Laboratory research reveals that subliminal stimuli has a subtle, fleeting effect that may prime (or heighten) a feeling that already exists. Research in subliminal priming confirms that much of our information processing occurs automatically without detection by our conscious mind and supports evidence in the powers of intuition.

25. 25 Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation. Put a band aid on your arm and after awhile you don’t sense it.

26. 26 Now you see, now you don’t