The JND is a constant fraction of the stimulus. - ️️•JND / I = K
I= intensity of the standard
K = a constant that is characteristic of the task ("Weber fraction")
conditions: - ️️-cataract - an opaque (or less transparent) area in the lens•some
caused by UV in sunlight; common in ag...
SJSU PSYC 158 Exam 1
The JND is a constant fraction of the stimulus. - ✔️✔️•JND / I = K
I= intensity of the standard
K = a constant that is characteristic of the task ("Weber fraction")
conditions: - ✔️✔️-cataract - an opaque (or less transparent) area in the lens•some
caused by UV in sunlight; common in aged•cured by removing lens, use glasses instead
(but...)
perception - ✔️✔️conscious experience of objects and their relationships (resulting
from psychological processes in which meaning, relationships, context, judgment, past
experience, and memory may play a role)
-e.g., your awareness of seeing a cat
Psychophysics - ✔️✔️the study of the quantitative relationship between physical
properties of the world and our psychological perception of these properties
Gustav Fechner
absolute threshold - ✔️✔️the smallest amount of stimulus energy necessary to detect a
stimulus•e.g., What is the dimmest light that you can detect?
psychometric function - ✔️✔️curve of percentage detection versus intensity
I. Method of Limits - ✔️✔️begin with undetectable stimulus; gradually increase intensity
until subject detects it (and vice versa)•
subject responds yes or no
below threshold, you would never detect
above threshold, you would always detect
absolute threshold is the intensity that is detected 50% of the time
II. Method of Adjustment - ✔️✔️•a variant of Method of Limits
•start with undetectable stimulus
•subject presses button to make stimulus stronger
, •stop when they detect the stimulus
•(and vice versa - start with detectable and adjust until undetectable)
III. Method of Constant Stimuli - ✔️✔️•similar to Method of Limits, except stimuli are not
presented in order of strength (rather, random order)
•subject does not know what change to expect
sensation - ✔️✔️initial processes of detecting and encoding environmental energy
Difference Threshold - ✔️✔️•a.k.a. just noticeable difference (JND)
•smallest difference between two stimuli that a person can detect
•as the magnitude of the stimulus increases, the difference threshold increases
physiological - ✔️✔️-invasive
•lesion
•ablation - creating lesions
•single cell recordings
non-invasive - ✔️✔️•EEG - electrical fields
•fMRI, PET, CAT - brain imaging
•TMS - magnetic shock temporarily disrupts region
psychological - ✔️✔️-detection-discrimination
- telling the difference between 2 stimuli-matching
- pick the one that matches the model-scaling
- ordering-identification
photons - ✔️✔️- tiny particles of light; the smallest units of light
waves - ✔️✔️- tiny oscillations of molecules
wavelength - ✔️✔️- how far the wave travels between oscillations
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