Psychology 1000 Lecture Notes - Lecture 5: Morphine, Subliminal Stimuli, Auditory Cortex
7 May 2018
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Chapter 5: Sensation and Perception
The Basics
Sensation - Stimulation of the sense organs (visual receptors, auditory receptors, taste buds).
Perception - Selection, organization, and interpretation of sensory input.
Ex. You look with your eyes (sensation) but see with your brain (perception)
Psychophysics - the study of how physical stimuli are translated into psychological experience. (i.e.
studies the relation between sensation and perception).
Sensory Integration: How sensations turn into perception (5-step process).
Psychophysics
- Stimulus: Information in the environment (touch, sound waves, light waves, etc.) that is picked up by
our sensory receptors. Any sensation begins with a detectable stimulus.
- Concerned with 2 kinds of sensitivity to stimuli: Absolute Limits of Sensitivity and Differences
between Stimuli:
1) Absolute Limits of Sensitivity How intense must a stimulus be for us to detect it 50% of the time?
(The lower the absolute threshold, the greater sensitivity).
2) Signal Detection Theory Absolute Threshold is not fixed. Situational factors can influence sensory
judgements. When the perception is more important, people have lower absolute thresholds
(Perception is essentially a decision).
3) The Difference Threshold (JND) How much does a stimulus need to be changed in order for us to
detect it? (Ex. what is the minimum amount that you need to turn the stereo down for your parents to
notice that it is not as loud?).
Wee’s Law - States that the difference threshold is proportional to magnitude of stimulus.
Varies for every stimulus :
Audition (Tonal pitch) 1/333
Vision (brightness) 1/60
Pain (heat reduced) 1/30
Audition (loudness) 1/20
Taste (salt concentration) 1/3
Ex. To just notice that a light is brighter, you have to increase the original brightness by a factor of 1/60
(the smaller the fraction, the more sensitive the sensory organ is).
SUBLIMINAL STIMULI: Stimuli that register on our NS but are below our sensory threshold. Research
shows that subliminal stimuli have little effect on our behavior and just a small effect on our attitudes
and emotional priming.
Wee’s La eaks do at eteel high
and low intensities
Most sensitive stimulus: pitch, brightness
Least sensitive stimulus: smell, taste
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Audition
The Stimulus: Sound waves (pressure waves in a medium). Our sensory register for audition is our ears.
Outer ear: The pinna collects sound waves and channels them down the ear canal, the sound waves put
pressure on the ear drum (tympanic membranes) which oscillates the 3 bones and amplifies the sound
to the oval window.
Note: The inner ear contains vestibular sacs that are used for balance and equilibrium (vestibular
system).
Auditory Transduction
- When sound waves strike the eardrum, pressure created at the oval window by the hammer, anvil and
stirrup sets the fluid inside the cochlea into motion which vibrates the basilar membrane causing the
hair cells in the organ of corti to vibrate. This bending of the hair cells triggers a release of
neurotransmitters into the synaptic space between hair cells and the neurons of the auditory nerve,
resulting in nerve impulses sent to the temporal lobe that respond to specific types of auditory input.
Perception of Loudness
Louder sounds are high-amplitude waves that cause hair cells to bend more and release more
neurotransmitter substance at the point of synapse with auditory nerve cells which results in high rate
of firing w/in auditory nerves. In addition, certain cells only respond to very loud sounds.
Thus, loudness is coded in terms of:
1. Rate of firing in the axons of the auditory nerve
2. Certain cells that respond to very loud cells
Perception of Pitch
1. Frequency Theory Nerve impulses/second sent to the brain match the frequency of the sound
Ex. Sound of 100HZ would mean fire 100 times/second
Pole: Neuos a’t fie oe tha ties/seod, so this is ol useful fo feueies ude
1000 Hz.
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Document Summary
Sensation - stimulation of the sense organs (visual receptors, auditory receptors, taste buds). Perception - selection, organization, and interpretation of sensory input. You look with your eyes (sensation) but see with your brain (perception) Psychophysics - the study of how physical stimuli are translated into psychological experience. (i. e. studies the relation between sensation and perception). Sensory integration: how sensations turn into perception (5-step process). Stimulus: information in the environment (touch, sound waves, light waves, etc. ) that is picked up by our sensory receptors. We(cid:271)e(cid:396)"s law - states that the difference threshold is proportional to magnitude of stimulus. We(cid:271)e(cid:396)"s la(cid:449) (cid:271)(cid:396)eaks do(cid:449)(cid:374) at e(cid:454)t(cid:396)e(cid:373)el(cid:455) high and low intensities. To just notice that a light is brighter, you have to increase the original brightness by a factor of 1/60 (the smaller the fraction, the more sensitive the sensory organ is). Subliminal stimuli: stimuli that register on our ns but are below our sensory threshold.
