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Unit 7: Sensation & Perception

Unit 7: Sensation & Perception. Sensation. Sensory systems enable organisms to obtain necessary information for survival

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Unit 7: Sensation & Perception

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  1. Unit 7: Sensation & Perception

  2. Sensation • Sensory systems enable organisms to obtain necessary information for survival • Example: a frog has eyes with receptors that are designed to detect the movement of small black shapes, but a frog would starve to death if it were knee-deep in motionless flies • Example: the human ear is designed to be most receptive to a baby’s cry • We are constantly bombarded with all kinds of stimuli, some of which we are highly sensitive to, many of which we are completely unable to detect • Ultra low or high frequency sound waves (elephants)

  3. Sensation • Absolute threshold: minimum stimulation necessary to detect a particular stimulus • Light, sound, pressure, taste, odor • Stimulus below the absolute threshold can not be detected • E.g. ultraviolet light • We measure absolute threshold by recording the stimulation necessary for someone to pinpoint its appearance 50% of the time.

  4. Absolute Threshold • Absolute Threshold

  5. Absolute Threshold Subliminal

  6. Absolute Threshold • Subliminal Stimuli = below one’s absolute threshold for conscious awareness • It was once believed that advertisers would manipulate consumers by flashing messages for incredibly brief moments of time during movies and television • Are we able to detect these subliminal stimuli? • Can subliminal stimuli still impact us?

  7. Subliminal Stimulation • Remember: the absolute threshold represents the amount of stimulation for us to detect a stimuli 50% of the time • Therefore, below this threshold we are still able to detect stimuli SOME of the time • Research has shown that subliminal stimuli can actually impact us • Rating images of people • Priming us to respond later

  8. Difference Thresholds • As well as being able to detect the presence of a minute stimuli, we must also be able to detect small differences as a stimuli changes • Difference threshold = the minimum difference a person can detect between any two stimuli • Just Noticeable Difference (JND) • The JND is not a constant, fixed value • Depends upon the magnitude of the stimulus

  9. Difference Threshold • Example: • If you add 10g to a 100g weight and you WILL notice the difference • If you add 10g to a 100kg weight, and you will NOT notice the difference • The change in stimulus was constant, but the different threshold was increased because of the increased magnitude of the stimulus • When the magnitude increases, the value of the JND also increases

  10. Difference Threshold • Weber’s Law = to perceive a difference in stimuli, they must differ by a constant percentage (not amount). • Different for each type of sensory information • Light = 8% • Weight (pressure) = 2% • Sound = 0.3%

  11. Difference Threshold Class Question: • Imagine you are in charge of designing a new coin system for Ghana. • Why would it be useful to apply the principles of the JND in your design? • Think of an example from your own activities today that demonstrates sensory adaptation for light, sound, and pressure.

  12. Sensory Adaptation • When a stimulus is presented constantly, we become insensitive to it • Example: Move your watch up an inch on your wrist, and you will notice it for only a few minutes • Sensory adaptation = our diminished sensitivity to unchanging stimulus • What about vision?

  13. Demonstration • Sensory Adaptation for taste

  14. Class Activity: • Remember: Psychology is a science • Design a procedure to determine the JND for either light, sound, smell, taste, or pressure.

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