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47 Cards in this Set
- Front
- Back
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Why study perception? |
-Future careers involved -Medical applications -Understand how we perceive the world |
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Why is it important to study perception objectively? |
Because it's often not possible to know what people perceive based on external stimuli. |
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What are the 7 steps in the Perceptual process? |
1. Environmental stimulus 2. Light is reflected and transformed 3. Receptor processes 4. Neural processing 5. Perception 6. Recognition 7. Action |
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What does Step One and Two Involve? (Stimuli) |
-Environmental stimuli -Principle of transformation -Sensory receptors |
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What is environmental stimuli? |
All objects available to observer in the environment |
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What is the principle of transformation? |
The stimulus and perception aren't the same, there is a transformation from the stimulus to electromagnetic energy to electrical signals |
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What are sensory receptors? |
Cells specialized to respond to environmental energy |
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What does Step Three involve? (Receptor processes/transduction) |
Visual pigment reacts to light. Transduction occurs and changes environmental energy into nerve impulses. -Transduction -Rods and cones |
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What is transduction? |
transformation of one energy form to another |
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What do rod and cone photoreceptors do? |
They line the back of the eye and change light energy into electrical energy, influencing what we perceive |
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What does Step 4 involve? (neural processing) |
-Neural processing -Primary receiving areas |
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What is neural processing? |
The changes that occur as signals are transmitted through thousands of neurons |
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What are the primary receiving areas for each of the sensory systems? |
Occipital lobe= vision Temporal lobe= hearing Parietal lobe= skin sense Frontal lobe= signals from all senses |
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Where does neural processing take place? |
In interconnected circuits of neurons and other complex circuits in the brain. Each sense sends signals to different areas of the brain. |
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What does step five to seven involve? (behavioral responses) |
-Perception -Recognition -Action |
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What is perception? |
Occurs as a conscious experience, we are aware of the stimulus |
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What is recognition? |
Occurs when an object is placed in a category, giving it meaning |
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What is action? |
Occurs when the person perceiving the stimulus initiates motor activity in response to recognition |
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KNOWLEDGE What is knowledge? |
Any info the perceiver brings to a situation |
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What is bottom up processing? |
Processing based on incoming stimuli from the environment, begins with stimulation of receptors |
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What is top down processing? |
Based on previous knowledge or cognitive factors |
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What is principle of representation? |
Everything a person perceives is based not on direct contact with stimuli, but on representations of stimuli that are formed on the receptors and activity in the nervous system |
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What is visual form agnosia? |
An inability to recognize objects |
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What did the rat-man demonstration show? |
How recently acquired info can influence perception, involving top down processing |
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STUDYING PERCEPTION What is the oblique effect? |
Better detail vision and sensitivity for verticals or horizontals (ferrets horizontal, humans both) compared to slanted lines |
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What is the psychophysical approach? |
Measures the relationship between the stimuli and perception (ex. subjects are tested to see how well they could see fine lines) |
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What is psychophysics? |
Study of the relationship between physical stimulus and our perception of it in our brain (developed by Gustav Fechner) |
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What is the physiological approach? |
Measures two relationships: 1. The one between stimuli and physiological responses 2. The relationship between physiological responses and behavioural responses (ex. measuring brain responses to stimuli) |
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BEHAVIORAL APPROACHES What are some behavioural approaches? |
1. Psychophysical methods: detection and discrimination 2. Perceiving magnitude: magnitude estimation |
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What is an absolute threshold? |
-the smallest amount of energy needed to detect a stimulus -the point where the subject says they see the light 50% of the time -idealized threshold at level 4 |
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CLASSIC PSYCHOPHYSICAL METHOD What are classic psychophysical methods? |
1. Method of adjustment 2. Method of Limits 3. Method of constant stimuli |
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What is method of adjustment? |
-Observer adjusts the stimulus intensity until it's detectable -Settings averaged to provide a threshold estimate PROS: more variable, fast, easy for observer CONS: subject to bias since observer controls intensity and knows whats being measured |
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What is method of limits? |
-Ascending trials alternate with descending trials (ex. hearing a tone) -Starting point varies from trial to trial -Calculates the average of all crossover points PROS: observer can't memorize pattern, less change of bias, done by experimenter CONS: still aware of stimulus, time consuming |
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What is the staircase procedure? |
-A trial begins at some intensity below or above the threshold. -When stimulus is presented and is detected, the next trial is reduced in intensity. -Threshold is average of reversals (continues until 15-20 reversals) PROS: observer loses track of what staircase they're on and can't predict increase/decrease, deals with habituation and expectation |
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What is method of constant stimuli? |
-Range of test values (ex. 7-11) are selected for subject's threshold -Stimuli presented 20 times in random order -Psychometric function is plotted -Find 50% point (threshold) -Method of adjustment used to determine test value ranges before MOCS PROS: precise with less bias |
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What does the slope show? |
Steep slope= high precision (low variability) Slope tells us how precise the observer is and gives an idea of accuracy. |
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DIFFERENCE THRESHOLD What is the difference threshold/just noticeable difference? |
The smallest difference between two stimuli that a person can just detect |
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What is Weber's law? |
JND/S=K S=stimulus K=constant
JND= S*K |
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ESTIMATING MAGNITUDE How is magnitude estimated? (Developed by S.S. Stevens) |
We measure threshold perceptions with ME, indicating what the observer is experiencing. 1.Experimenter presents a standard stimulus (ex. light) 2.Assigns it a value (ex. 10) 3.They present different intensities 4.Ask subject to assign a number to each light in relation to the original one |
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What is perceived magnitude? |
the number for intensity of the stimulus |
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What is response compression and expansion? |
Compression: the increase in perceived magnitude is smaller than the increase in stimulus intensity (slope -<1) Expansion: as intensity is increased, perceptual magnitude increases more than stimulus intensity (slope >1) |
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What does reaction time depend on? |
-Intensity and duration of stimulus -Which sense is stimulated -Personal attributes -Usually more complex operations take longer (ex. mental rotation task, visual search task, difficult conjunction search) |
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SIGNAL DETECTION THEORY Why is SDT useful? |
In classic methods there are no ways to separate sensitivity from response criteria. SDT can be used to assess thresholds separately. |
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What is SDT? |
-Only one stimulus intensity is presented, on some trials none is presented. -Results come in four types: 1. Hit- correct response 2. Miss- saying no when it is present 3. False Alarm- saying yes when it isnt present 4. Correct rejection- saying no when there is no stimulus present |
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How is a person's sensitivity indicated? |
It's indicated on the probability distribution by the distance between the peaks of N and Signal+Noise distributions (more sensitive, larger separation) |
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RECEIVER OPERATING CHARACTERISTIC CURVE (ROC) What does the shape of the ROC curve show? |
It shows each person's sensitivity. Overall sensitivity can be known by taking into account different response criteria. |
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What is plotted? |
Results from the liberal, conservative, and neutral responses are plotted using the percentage of hits vs. false alarms. High sensitivity= bowed ROC curve Low= flatter curve |
