369 Perceptual

Asking what changes in physical intensity to we need to just discriminate stimuli at a number of different supratheshold.

Aka. just noticeable difference /JND/ and difference limen

–minimum intensity difference that is noticeable to the observer

A change in intensity that is smaller than the difference threshold

A change in intensity that is larger than the difference threshold:

•Presenting one stimulus at a time •The stimulus is very weak •Possible responses:
“Yes, I see it.” /
“No, I don’t see it.”

•Presenting two stimuli at a time: –Standard: fixed, easily detectable –Comparison: either more or less intense than the standard •Possible responses:
“Comparison is stronger.” /
“Comparison is weaker.”

The average of Ds and Dw

•intensity difference between the standard and comparison stimuli where the response changes

üwe need larger changes in the S to notice a jnd when S is of high intensity

üpsychological responses (jnds) increase constantly as S intensity increases geometically

üthe psyc response (mag) in related to the S intensity raised to aparticluar power and in general is more accurate than the other laws.

Whats the 3 functional slopes from differential thresholds

Is difference threshold constant?

•difference threshold is a constant proportion of the initial stimulus value