Psychophysics Flashcards
Response expansion
the result when doubling the physical intensity of a stimulus more than doubles the subjective magnitude of the stimulus
Response compression
the result when doubling the physical intensity of a stimulus less than doubles the subjective magnitude of the stimulus
Goal of psychophysics
to describe the relationship between the physical world and the mind
Absolute threshold (method of limits)
experimenter presents successively lower (or higher) intensity until it is no longer perceived (or just noticed)
Gustav Teodor Fechner
wanted to create a scientific study of the relationship between the body and the soul; developed ways to measure perception
Absolute threshold (method of constant stimuli)
Present subject with predetermined stimuli at different levels
Absolute threshold (method of adjustment)
is a special case of method of limits where the participants adjusts the intensity levels themselves
Measured absolute threshold
point where the stimulus is noticed 50% of the time (50% of participants detect the stimulus)
Liberal strategy
“yes” (even though they aren’t sure, they will say yes)
Conservative strategy
“no” (even though they aren’t sure, they will say no)
Ex. lucy says “yes” on 90 trials. This correct response –saying “yes” when a stimulus is present
called a hit (tone is present)
Ex. Lucy says “no” on 10 trials. This incorrect response – saying “no” when a stimulus is present
called a miss (tone is present)
Ex. Lucy says “yes” on 40 trials. This incorrect response – saying “yes” when there is no stimulus
called a false alarm
Define the difference threshold (DL)
The difference threshold (or Just Noticeable Difference - JND) is the smallest change in a stimulus that a person can detect. It represents the minimum amount by which two stimuli must differ for someone to notice the change. This concept helps us understand how sensitive our senses are to detecting variations in things like brightness, sound, or taste. The idea is linked to Weber’s Law, which states that the noticeable difference is proportional to the initial intensity of the stimulus.
Ex. Lucy says “no” on 60 trials. This correct response – saying “no” when there is no stimulus
called correct rejection
Explain the relationship between DL and jnd
The relationship between DL (difference threshold) and JND (Just Noticeable Difference) is straightforward, as the terms are essentially synonymous. Both DL and JND refer to the smallest detectable change in a stimulus that an individual can perceive. In other words, they represent the minimum amount by which two stimuli must differ for a person to notice that they are not the same.
DL and JND are often used interchangeably in discussions related to psychophysics, the branch of psychology that studies the relationship between physical stimuli and the psychological sensations they evoke. These terms are crucial for understanding the limits of human sensory perception and the sensitivity of our senses to changes in the environment. The idea behind both concepts is to quantify the smallest change that a person can reliably detect in various sensory experiences, such as vision, hearing, taste, and touch
Describe the experimental procedure of magnitude estimation
In magnitude estimation, participants assign numerical values to the perceived intensity of stimuli, allowing researchers to understand the perceived magnitudes of different stimuli
Describe how steven’s power law is connected to out perceived change in stimulus intensity
Steven’s Power Law is a mathematical relationship between the perceived intensity of a stimulus (S) and the physical intensity of that stimulus (I). It is expressed as S = a * (I^n), where ‘a’ is a constant and ‘n’ is an exponent.
The exponent ‘n’ in the equation reflects the subjective scaling of perceived intensity. Different values of ‘n’ represent different relationships between physical and perceived intensity.
Describe the terms in an outcome matrix
An outcome matrix is a table that summarizes the results of signal detection experiments. It typically includes categories such as hits, misses, correct rejections, and false alarms, providing a comprehensive view of an observer’s responses to stimuli
Compare the difference between noise and signal + noise probability distribution
Noise: represents random variability or background activity that may interfere with signal detection
Signal + Noise: represents the combination of the actual signal and background noise in a probability distribution
Explain how the criterion is related to hits, misses, correct rejections and false alarms
The criterion is the decision threshold an observer uses to determine whether a stimulus is present or absent. It influences the balance between hits, misses, correct rejections, and false alarms
Describe and give examples of how payoffs can alter the criterion
Payoffs, or consequences associated with correct and incorrect responses, can influence an observer’s decision criterion. Higher payoffs for hist or correct rejections may lead to a more conservative criterion, while higher payoffs for false alarms may result in a more liberal criterion
Explain what an ROC curve is, how it is created, and how it’s related to discriminability
ROC: a graphical representation of the relationship between the true positive rate (sensitivity) and false positive rate (1 - specificity) at various decision criteria. It is created by plotting these rates against each other
The ROC curve provides a visual representation of how well an observer can discriminate between signal and noise, with a steeper curve indicating better discriminability
Explain how discriminability is related to probability distributions
Discriminability is the ability to distinguish between signal and noise. Probability distributions help illustrate the likelihood of different outcomes, such as hits and false alarms, given a specific level of discriminability
