GRE Psychology Subject Test -- Sensation and
Perception questions with verified answers
Weber's Law Ans✓✓-the principle that, to be perceived as different, two stimuli
must differ by a constant minimum percentage (rather than a constant amount).
Whats important in producing a JND is not the absolute difference between the
two stimuli, but the ratio of them. Just noticebale difference. This law was
discovered by Gustav Fechner
Mathematically, this can be expressed as ? I/I=K OR ? S/S =K
I= change in intensity
K= Webers Fraction OR Webers Constant - the smaller the K the better the
sensitivty
See candle example in the book.
Ernest Weber Ans✓✓-His book, De Tactu, introduced the notion of just
noticeable difference (JND) in sensation (See Webers Law)
Pyschophysics Ans✓✓-the study of relationships between the physical
characteristics of stimuli, such as their intensity, and our psychological experience
of them
Absolute Threshold Ans✓✓-the minimum intensity of stimulation that must occur
before you experience a sensation. For example how light or how loud something
must be for us to percieve it.
, Subliminal Perception Ans✓✓-the processing of information by sensory systems
without conscious awareness
Difference Threshold Ans✓✓-how different two stimuli (in magnitutde) must be
before they are perceived to be different
just noticeable difference (JND) Ans✓✓-the minimal change in a stimulus that can
just barely be detected. This is related to the difference threshold
signal detection theory Ans✓✓-a theory predicting how and when we detect the
presence of a faint stimulus (signal) amid background stimulation (noise).
Assumes there is no single absolute threshold and that detection depends partly
on a person's experience, expectations, motivation, and alertness -- response bias
response bias Ans✓✓-Measures how risky the subject is in sensory decision-
making; based upon non-sensory factors (experiences, motivations, expectations)
Fechner's Law Ans✓✓-expresses the relationship between the intensity of the
sensation and the intensity of the stimulus. Its purpose is to relate the intensity of
the stimulus to the intensity of of the sensation. Determined the sensation
increases more slowly as intensity increases
Steven's Power Law Ans✓✓-It also relates the intensity of the stimulus to the
intensity of sensation.
ROC curve (receiver operating characteristic) Ans✓✓-curves employed by many
researchers to graphically summarize a subjects responses by measuring the
operating (sensitivity) charachterisitcs of a subject recieving signal. Used to
graphically summarize a subject's responses in a signal detection experiment.
Perception questions with verified answers
Weber's Law Ans✓✓-the principle that, to be perceived as different, two stimuli
must differ by a constant minimum percentage (rather than a constant amount).
Whats important in producing a JND is not the absolute difference between the
two stimuli, but the ratio of them. Just noticebale difference. This law was
discovered by Gustav Fechner
Mathematically, this can be expressed as ? I/I=K OR ? S/S =K
I= change in intensity
K= Webers Fraction OR Webers Constant - the smaller the K the better the
sensitivty
See candle example in the book.
Ernest Weber Ans✓✓-His book, De Tactu, introduced the notion of just
noticeable difference (JND) in sensation (See Webers Law)
Pyschophysics Ans✓✓-the study of relationships between the physical
characteristics of stimuli, such as their intensity, and our psychological experience
of them
Absolute Threshold Ans✓✓-the minimum intensity of stimulation that must occur
before you experience a sensation. For example how light or how loud something
must be for us to percieve it.
, Subliminal Perception Ans✓✓-the processing of information by sensory systems
without conscious awareness
Difference Threshold Ans✓✓-how different two stimuli (in magnitutde) must be
before they are perceived to be different
just noticeable difference (JND) Ans✓✓-the minimal change in a stimulus that can
just barely be detected. This is related to the difference threshold
signal detection theory Ans✓✓-a theory predicting how and when we detect the
presence of a faint stimulus (signal) amid background stimulation (noise).
Assumes there is no single absolute threshold and that detection depends partly
on a person's experience, expectations, motivation, and alertness -- response bias
response bias Ans✓✓-Measures how risky the subject is in sensory decision-
making; based upon non-sensory factors (experiences, motivations, expectations)
Fechner's Law Ans✓✓-expresses the relationship between the intensity of the
sensation and the intensity of the stimulus. Its purpose is to relate the intensity of
the stimulus to the intensity of of the sensation. Determined the sensation
increases more slowly as intensity increases
Steven's Power Law Ans✓✓-It also relates the intensity of the stimulus to the
intensity of sensation.
ROC curve (receiver operating characteristic) Ans✓✓-curves employed by many
researchers to graphically summarize a subjects responses by measuring the
operating (sensitivity) charachterisitcs of a subject recieving signal. Used to
graphically summarize a subject's responses in a signal detection experiment.
