Psychology 1000 Lecture Notes - Lecture 7: Subliminal Stimuli, Vitreous Body, Spectral Sensitivity

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2 Aug 2016
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October.27
Chapter five
Sensation
-Psychophysics
-Subliminal Perception
-Visual system
Next time: More vision
Scan: page 143-151
What do Weber fractions tell you about sensation?
Can we perceive subliminal subliminal messages?
How does the visual system work?
Sensation
How do we perceive the world around us?
Psychophysics and psychophysiology
Psychophysics
-Relation between physical stimulus and psychological response
-Fechner (father of psychophysics)
-Can determine a just noticeable difference
-JND
-Can figure out when things are different (ex. When lighting changes)
Threshold
-Value of a stimulus characteristic required to produce some response
-Absolute: Lower limit (tell us when sensory systems kick in)
Difference: Amount of change for JND
-Not 1 to 1 relationship (non-linear)
Weber’s law
-Size of difference threshold relative to physical intensity of test is constant
-If I=50 db and a JND is reported at 55 db
-Value of JND is not constants but the relative difference is
-Compare sensitivity of different systems
Fechner’s Law
-Sensation increases with the logarithm of intensity
-More general and cognitively economic
S= k log I
Compare Δ1
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Steven’s power law
-S= k log IN
-More predictive across a variety of sensations
-Most general
Subliminal perception
-Can we perceive stimuli that are below threshold?
-Is out behaviour affected by subliminal stimuli?
-James Vicary (1957)
-Claimed 50% increase in popcorn sales
-Made up this data
-Concern about the use of subliminal “cuts”
William Tapley
-Found shapes in structures
-In general there is no evidence that subliminal cuts influence consumer behaviour
-But consider Bruce and Valentine (1986)- priming
-Used priming
-Showed people photos 1 for 100 milliseconds, couldn’t identify it, but if the first photo was
related to the second you could identify the second quicker.
-Fitzsimons 2008
-30 milliseconds exposure to logos
-Influenced subtly
-Sperdin 2014
-Min presentation time for neural response
-250 microseconds (1/4000 sec)
Sensory systems
4 things in common
1.Accessory structures
ex. Outer ear
2. Transduction
-Receptors, take sensory signal (ex. Light) and convert it into neural signal
3. Coding
ex. Frequency
4. Interaction
-Physiological and psychological
The visual system
-Iris (coloured portion, spherer muscle, controls size of pupil)
-Pupil
-Cornea (protects the eye, major focus point of images)
-Lens (thick structure, allows to focus near and far)
-Vitreous humor (Inflates eyeball)
-Retina (Most sensitive portion, visual receptors)
-Foves(most sensitive part of retina)
-Optic never (composed of axons from retina)
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