Psycpysics Practice Qs Flashcards
When no stimulus is presented, even though observer asked
Blank trials
During a VF test, the patient is reluctant to signal that she sees the stimulus even when she may see it. The threshold criteria used by the patient is
Strict
When determining a clinical threshold, which psychophysical method most minimizes the important of a patients criterion?
Forced choice
Which method of threshold determination is commonly used during automated VF testing?
Staircase
Which of the following forced-choice clinical procedures is expected to result in the least steep (shallowest) psychometric function
2AFC
A response in which the subject reports not seeing a clearly visible, Supra-threshold stimulus is referred to as a
False negative
The Jackson crossed cylinder tests for measuring astigmatism is an example of which fo the following psychophysical methods
Forced choice
If the chance performance of an 4AFC method experiment is 25% what is the threshold of this 4AFC method?
62.5
When a patient adopts a strict criterion during clinical test, as opposed to a lax criterion, the result is relatively
Few false positives and few hits
If the VA of a patient who has a strict criterion is determined with the endothelium of descending limits alone, the measure VA is likely to be
Betterthan it actually is
Ocular disease is expected to cause the slope of the psychometric function to
Decrease
Webers law predicts that as background intensity increases, contrast threshold
Remains constant
When measuring VA with a typical snellen VA test, which psychophysical methods will provide the most reliable result
Descending limit
Combined with forced choice
As the intensity of the background surrounding a patch of light increases, the background of the patch
Decreases
According to signal detection theory, a stimulus produces neural activity that is
Randomly distributed over time
For a given detecatblilty, as the probability of a hit increases, the probability of a false positive
Increases
The method of constant stimuli is designed to keep what constant from trial to trial
Subjects expectations and stimulus intensity
As the stimulus size increases, the detectaobility of the stimulus
Increases
?
The appearance of the E is the same under both dim and bright lighting conditions, as long as it obeys Weber’s law. This phenomenon is referred to as
Light constancy
If an observers repsonse is correct reject, then the neural activation is
Below the criterion
