PSYC101 Lecture Notes - Detection Theory, Subjective Constancy, Absolute Threshold
10 Jun 2018
School
Department
Course
Professor
Perception
Lecture Overview
Thresholds of sensations – Signal detection theory
•
Visual perception: depth perception, perceptual constancies, and visual
illusions
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Theories of perception: Bottom – up, top-down, and gestalt approaches
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Attention
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Application of research on perception
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Basic Concepts
Sensation: Stimulation of sense organs
Absorption of energy
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Perception: Organisation of sensory information and interpretation of input
Translating sensory input into something meaningful
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Elements of a Sensory System
The progress of sensation:
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Accessory struture modifies energy
1.
Receptor tranduces energy
2.
Sensory nerves bring encoded information of CNS
3.
Initial processing in the thalamus (except for smell)
4.
Processing in cerebral cortex produces preception (last piece of converting
energy)
5.
Perception Paradox
Although perception seems so quick and easy it is an incredibly complex
process
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Failures of perception
Perceptual illusions
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Threshold of Sensation
Psychophysics and the Absolute Threshold
Early psychologists were greatly intersted in the experience of sensation
Psychophysics: relationship of physical energy in the environment and
psychological experience
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•
Week 7 –Lecture
Friday, 5 May 2017
4:29 PM
find more resources at oneclass.com
find more resources at oneclass.com
psychological experience
Thresholds: What is the minimum amount of energy required for detection of
a stimuls?
Absolute threshold: Minimum intensity detectable by an organism
No single intensity that mans a person is suddenly able to detect
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Intensity when the stimulus is detected 50% of the time
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The Absolute Threshold
The minimum amount of energy that can be detected 50% of the time
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Supraliminal stimulation: refers to a stimulus going to detect more the 50% of
the time
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Subliminal stimulation: refers to a stimulus not going to detect 50% of the
time
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Thresholds
Vary between people and situations
Distraction of other noises
Internal (Neurons firing) and external (concert)
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Psychological distractions
Stress and fatigue
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Is something out there?
Signal detection theory: Key point in the SDT is that detection involves
decision processes and sensory processes
Judgement call about the presence of a stimulus
Influence by 'noise' (irrelevant stimuli and neural activity)
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First process: sensory which reflects individual differences
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Second process: Response bias or decision criteria
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Signal Detection
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find more resources at oneclass.com
Sensitivity:
Intensity of the signal
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Capacity of sensory system
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Affected by 'noise' level
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Response criterion
Willingness to respond to a stimulus
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Influenced by motivation and expectancies
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Response bias: Present stimuli at low intensities
Stimuli and no-stimuli trails
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Can make two types of error
False alarm; Responding when there is no signal
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Fall to report
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Can make two correct responses
Correct positive: as it increases false alarm increases
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Correct negative: as it increase (nope nothing is there) you might
fail to report
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Trade-off between stimuli sensitivity and vulnerability to errors
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Response bias:
High or low response bias depends on many factors
Expectations
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Motivation
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Performance when detecting stimuli depends on:
Your criterion
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The 'noise'
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Intensity of the stimuli
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Perception Without Awareness
Can stimuli be detected even if it is below the threshold of awareness?
Subliminal perception
'Eat popcorn' flashing imperceptibly is a film
Increase in sale of 58%
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▪
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Generally only weak effects are seen
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Judging differences Between Stimuli
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Visual perception: depth perception, perceptual constancies, and visual illusions. Theories of perception: bottom up, top-down, and gestalt approaches. Perception: organisation of sensory information and interpretation of input. Initial processing in the thalamus (except for smell) Processing in cerebral cortex produces preception (last piece of converting energy) Although perception seems so quick and easy it is an incredibly complex process. Early psychologists were greatly intersted in the experience of sensation. Psychophysics: relationship of physical energy in the environment and psychological experience psychological experience. Absolute threshold: minimum intensity detectable by an organism. No single intensity that mans a person is suddenly able to detect. Intensity when the stimulus is detected 50% of the time. The minimum amount of energy that can be detected 50% of the time. Supraliminal stimulation: refers to a stimulus going to detect more the 50% of the time. Subliminal stimulation: refers to a stimulus not going to detect 50% of the time.
