6. Measuring Vision Flashcards
The Stroop effect
An interference effect where reaction time is slower due to automatic processing of incongruent information
Two direct applications of the Stroop effect
- Studying grapheme-colour synaesthesia
- Mapping colour appearance
These are both ___________
Name and describe an indirect application of the Stroop effect, and what it has been used for.
The implicit association test is an __________________.
- It tests strength of associations to measure attitudes
- Subjects categorise words along two dimensions
- Easier/faster response pairings indicate that pairing is more strongly associated in memory, which indicates an underlying attitude.
- This test has been adapted to test psychopaths attitudes to violence
What is a threshold, and what is it used for?
The lowest stimulus level that you can reliably detect/discriminate.
This is a measure used to quantify behaviour.
How are thresholds and sensitivity related?
_____________________ are inversely related. The more stimulus you need, the higher the __________, and the poorer the _________. This is expressed in log10.
Give an example of a detection task
An example of __________:
How dim can I make a single light and still see it?
Give an example of a discrimination task.
What’s the smallest difference in luminance between two lights I can see?
Which is more reliable - a detection task or a discrimination task? Why?
Detection requires criterion or what constitutes sufficient evidence, which will be different for everyone. Discrimination is criterion free.
This means that a discrimination task is __________
What are four methods of measuring vision?
- Adjustment
- Method of constant stimuli
- Method of limits
- Staircase
These are all ______________
Acuity
________ is:
- Threshold size
- The most popular clinical measure of visual function
How would you measure acuity with the adjustment method? What are its caveats?
Adjust with the dial until the letter is a size where you can just read it, then report which letter you are seeing.
Caveats: criterion in choosing size, slow process.
What is this an example of?
How would you measure acuity with the method of constant stimuli? What are its caveats?
Letters are shown one at a time at a variety of different sizes. Participant must report which letter they are seeing. Their answers do not change the stimuli they are shown.
Caveats: effeciency and speed (the one size fits all nature of the task is not ideal).
What is this an example of?
How would you measure acuity with the method of limits?
A mixture of two kinds of trials:
Descending _____________: the letters start large and then you shrink the letters until the subject gets the task wrong.
Ascending ____________: the letters start small and then get larger until the subject gets the task right.
This is an example of ________________.
How would you measure acuity with the staricase method? What are its caveats?
Present a stimulus in discrete steps of increasing or decreasing visibility. Alter step direction at each change in performance (reversal).
Very efficient and adaptive - but caveat: anticipation
What is this an example of?
What are forced choice tasks, and what is their advantage?
The psychometric function is generated by measuring responses to multiple stimuli with the subject always responding. The subject is given two or more choices.
Advantage: no criterion, bias can be controlled.
What am I?
Point of subjective equality
_________________ is the point where the subject has a 50% chance of picking either option, thus perceiving them to be equal. This is a way of measuring the effect of an illusion.
How can you read the following two abilities on a psychometric curve?
- Discrimination ability/sensitivity (threshold/JND)
- Illusion strength
What do the following two parts of a psychometric curve tell us about?
- The slope =
- The shift =
Weber-Feshner law of discrimination
The more there is of a stimulus, the harder it is to detect change in it.
OR Resolution (aka your threshold for detecting change / just noticeable difference) decreases with stimulus magnitude.
What is this?
How is the Weber-Feshner law explained?
_____________ is explained by multiplicative noise: uncertainty scales with the size of the stimulus.
Neurons become more variable the more they fire, so we become poorer at making discriminations of change in stimuli that are at larger magnitude.
Reverse card!
An interference effect where reaction time is slower due to automatic processing of incongruent information
The Stroop effect
Reverse card!
- Studying grapheme-colour synaesthesia
- Mapping colour appearance
These are both ___________
Two direct applications of the Stroop effect
Reverse card!
The implicit association test is an __________________.
- It tests strength of associations to measure attitudes
- Subjects categorise words along two dimensions
- Easier/faster response pairings indicate that pairing is more strongly associated in memory, which indicates an underlying attitude.
- This test has been adapted to test psychopaths attitudes to violence
Name and describe an indirect application of the Stroop effect, and what it has been used for.
Reverse card!
The lowest stimulus level that you can reliably detect/discriminate.
This is a measure used to quantify behaviour.
What is a threshold, and what is it used for?
Reverse card!
_____________________ are inversely related. The more stimulus you need, the higher the __________, and the poorer the _________. This is expressed in log10.
How are thresholds and sensitivity related?
Reverse card!
An example of __________:
How dim can I make a single light and still see it?
Give an example of a detection task
Reverse card!
What’s the smallest difference in luminance between two lights I can see?
Give an example of a discrimination task.
Reverse card!
Detection requires criterion or what constitutes sufficient evidence, which will be different for everyone. Discrimination is criterion free.
This means that a discrimination task is __________
Which is more reliable - a detection task or a discrimination task? Why?
Reverse card!
- Adjustment
- Method of constant stimuli
- Method of limits
- Staircase
These are all ______________
What are four methods of measuring vision?
Reverse card!
________ is:
- Threshold size
- The most popular clinical measure of visual function
Acuity
Reverse card!
Adjust with the dial until the letter is a size where you can just read it, then report which letter you are seeing.
Caveats: criterion in choosing letter, slow process.
What is this an example of?
How would you measure acuity with the adjustment method? What are its caveats?
Reverse card!
Letters are shown one at a time at a variety of different sizes. Participant must report which letter they are seeing. Their answers do not change the stimuli they are shown.
Caveats: effeciency and speed (the one size fits all nature of the task is not ideal).
What is this an example of?
How would you measure acuity with the method of constant stimuli? What are its caveats?
Reverse card!
A mixture of two kinds of trials:
Descending ______________: the letters start large and then you shrink the letters until the subject gets the task wrong.
Ascending ______________: the letters start small and then get larger until the subject gets the task right.
This is an example of ________________.
How would you measure acuity with the method of limits?
Reverse card!
Present a stimulus in discrete steps of increasing or decreasing visibility. Alter step direction at each change in performance (reversal).
Very efficient and adaptive - but caveat: anticipation
What is this an example of?
How would you measure acuity with the staricase method? What are its caveats?
Reverse card!
The psychometric function is generated by measuring responses to multiple stimuli with the subject always responding. The subject is given two or more choices.
Advantage: no criterion, bias can be controlled.
What am I?
What are forced choice tasks, and what is their advantage?
Reverse card!
_________________ is the point where the subject has a 50% chance of picking either option, thus perceiving them to be equal. This is a way of measuring the effect of an illusion.
Point of subjective equality
Reverse card!
What do the following two parts of a psychometric curve tell us about?
- The slope =
- The shift =
How can you read the following two abilities on a psychometric curve?
- Discrimination ability/sensitivity (threshold/JND)
- Illusion strength
Reverse card!
The more there is of a stimulus, the harder it is to detect change in it.
OR Resolution (aka your threshold for detecting change / just noticeable difference) decreases with stimulus magnitude.
What is this?
Weber-Feshner law of discrimination
Reverse card!
_____________ is explained by multiplicative noise: uncertainty scales with the size of the stimulus.
Neurons become more variable the more they fire, so we become poorer at making discriminations of change in stimuli that are at larger magnitude.
How is the Weber-Feshner law explained?
