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85 Cards in this Set

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In method of limits testing the examiner
Manipulates the stimulus – either ascending or descending
In method of adjustment the subject
Manipulates the stimulus to match a standard
In method of constant stimuli the subject responds to
Independent measure – most accurate – a psychometric function is constructed – 50%response level – response independent
Scaling methods are used to determine the
Intensity of the sensation experienced by the subject
In direct scaling the subject
Assigns appropriate numbers to a series of stimuli according to the subjective impressions
Indirect scaling is broken down into
Comparative judgment and Categorical judgment
The four basic measurement scales are
1) nominal 2) ordinal 3) interval 4) ratio
Probability of correctly identifying a + = (sensitivity)
TP / (TP + FN) = hit rate
Probability of correctly identifying a – = (specificity)
TN / (TN + FP) =
Positive predictive value =
TP/ (TP +FP) probability that if labeled + is in fact +
Negative predictive value =
TN / (TN + FN) probability that if labeled – is in fact –
3 variables to describe color
1) hue 2) saturation 3) brightness
Hue is correlated with the
Wavelength of the light – photometric equivalent is dominant wavelength
Hue is best detected at
Blue green (490nm) and yellow red (590nm)
Saturation is a measures of the degree to which the
Stimulus is mixed with white – photometric equivalent is purity
Brightness is the
Luminosity of the color – photometric equivalent is luminance
Abney effect refers to
A change in hue associated with a change in purity (saturation)
Benzold Brucke effect refers to
A change in hue associated with a change in luminance - stimuli below 500nm look more blue with increased intensity- stimuli above 500nm look more yellow with increased intensity
Purdy effect is a
Change in saturation with a change in luminance
Best color discrimination for normals is
At 480-490nm (blue green) and 580nm (yellow)
For dicromats the best discrimination is at the ProtanopesDeuteranopesTritanopes
Neutral point 490nm495nm570nm
Additive primary colors are
Red, green, blue (yellow is a psychological primary)
Complementary colors when mixed produce
White or gray -
Additive color mixtures are a
Superimposition of 2 or more lights to produce a color
Metameric colors are colors that
Match in appearance but are composed of different wavelength mixtures
Simultaneous color contrast refers to the change in
The appearance of an object with a change in the surround color
Successive color contrast refers to a
Negative afterimage being the color of the complementary color
Color contingent aftereffects are due to
Fatigue/ adaptation of he system
The McCollough effect refers to an adaptation to
Orientation and color
Color constancy refers to the fact that
Relative colors remain constant with changes in luminance
Tristimulus values are the
Boundaries of visible spectrum (380-760nm)
Munsell color system attempts to have the
Notation correspond to the sensory experience
Munsell hues are located around a circle numbered
1-10 – there are 10 major hues and 100 total hues
The Munsell “value” refers to
Lightness and is along the vertical axis
The Munsell “chroma” refers to
Whiteness and is represented by a horizontal line from the center of the circle – scale form 0 to a maximum
The Munsell notation is given in
H/V/C hue/value/chroma
MacAdams ellipses are perceptual areas in the CIE diagram where
All colors will appear the same – even if physically different
Cones have the greatest sensitivity at
555nm (green/yellow)
Rods have the greatest sensitivity at
505nm (blue/green)
Anomalous trichromats Deuteranomaly ProtanomalyTritanomaly
Require 3 primary colors to create a match Most common of all deficiencies – requires more green to match color mixtures – M cones are mutated (535nm)Requires more red to match color mixtures – L cone defectiveRequires more blue to match color mixtures – S cone defective
Dichromats Protanope Deuteranope Tritanope
Require 2 primary colors to make a match Missing erythrolabe – confuse red with any other color and B-G with white – best color discrimination for 492nm (blue green) – cannot discriminate at long wavelengthsMissing chlorolabe – confuse green with white – nearly normal photopic spectral sensitivity – discriminate best for 498nm (greener blue green) Missing cyanolabe – confuse yellow with white – normal photopic spectral sensitivity – best discrimination for 570nm (yellow green)
Rayleigh equation is the ratio of
Red to green needed to match yellow in an anomaloscope
Protanomalous trichromats will have one ratio but will
Require more red than normal
Deuteranomalous trihromats will have one ratio but
Require more green than normal
Protanopia causes a px to require
Less luminance of yellow to match brightness of pure red
Deuteranopia requires equal
Luminance to match yellow with pure red or green
Kollner’s rule Diseases of retina and ocular mediaDiseases of the ON and visual pathway
Applies to acquired color vision defects Blue yellow defectRed green defects
Brightness can be predicted by
The activity of non opponent cells
Hue can be predicted by
The activity of opponent cells
Saturation can be predicted by
The ratio of opponent to non opponent cells
Oculocentric localization references objects in space to
The entrance pupil of the observing eye (monocular)
Every point on the retina has a visual direction
Associated with it = local sign
Primary visual direction is the
Local sign associated with the fovea
Secondary visual directions are associated with
All other retinal elements – are relative to the primary visual dir
Oculocentric visual direction refers to the fact that
Secondary visual direction is always relative to the primary visual direction
In egocentric localization direction is in reference to
The cyclopean eye – occurs at the cortical level – requires the input of two oculocentric locatozations – binocular
Around a horoptor, binocular disparity is
Zero
Geometric effect occurs with magnification in the
Horizontal meridian (X90) – floor slants down and toward magnified eye – facing wall is skewed away from eye
Induced effect occurs with magnification in the
Vertical meridian (X180) – floor slants up and away from the magnified eye – facing wall is skewed toward the eye
Visually guided behavior is controlled by the
Superior colliculus
Minimum visual acuity determines the
Presence or absence of a target – rod function
Resolution refers to a
Response to separation between elements of a pattern
Recognition requires
Naming of the test object or a critical aspect of it
Contrast =
(Target luminance – background) / background luminance
Contrast =
(Lmax- Lmin) / (Lmax + Lmin)
In an Ames room the
Perceived distance is constant but retinal image size varies
Mueller Lyer illusion refers to
Lines of same length appearing unequal due to arrow heads
Weber’s law states that
The higher the background, the higher the change in stimulus necessary for the detection of an absolute difference
DeVries-Rose Law predicts the
Ideal threshold of a stimulus upon a background
Ricco’s law deals with
Spatial summation – better in scotopic system
Block’s law deals with
Temporal summation – better in photopic system
The critical duration for temporal summation is
100msec for rods; 10-15msec for cones
Korte’s law summarizes the optimum stimulus
For apparent motion
Alpha motion is a type of apparent motion where there
Is apparent expansion and ceontration – 2nd target is larger
Gamma motion is a type of apparent motion where
The second target is brighter
Sigma motion occurs when the target is constantly on
The fovea
Stroboscopic movement (Phi phenomena) is where the
Presentation of stationary stimuli gives rise to apparent motion
Brucke-Bartley effect refers to a
Flickering light looking brighter than a steady light
Granit Harper law refers to the fact that as the
Size of a CFF stimulus increases the CFF becomes higher
Ferry Porter law states that the
CFF is directly proportional to the log of the stimulus intensity
Backward masking aka metacontrast is when the
Mask stimulus is presented immediately after the test stimulus
Forward masking aka paracontrast occurs when the
Mask precedes the stimulus