Sensation and Perception Practice for Test 2 (Chapters 4 through 6)

What is middle-level vision?

Between basic features of low-level vision and the object recognition and scene understanding of high-level vision

What does a color with maximum saturation look like?

Black

Which of the following was NOT an opponent process mechanism proposed by Hering?

Blue+, Green-

What are the opponent color sets in opponent color theory?

red vs. green, blue vs. yellow, and black vs. white.

Name two ways of solving the correspondence problem.

1) Blurring the image to remove high spatial frequencies, so that there are fewer dots to analyze; 2) using the uniqueness constraint in which a feature in the world is represented exactly once in each retinal image; or 3) using the continuity constraint which assumes that neighboring points in the world lie at similar distances from the viewer, except at the edges of objects.

What are the three steps of color perception?

1) Detection during which wavelengths of light are first registered by the visual system; 2) Discrimination during which different wavelengths of light are distinguished from each other; and 3) Appearance during which viewing conditions are taken into account while producing the final percept of a scene.

What are some of the assumptions that perceptual committees make?

1. The committees must "know" something about physics 2. The committees assume that we are not viewing a scene from an accidental viewpoint, which would mask the true structure of the objects in the scene

Color-matching experiments show that if a person with full-color vision is given at least ____ wavelengths of light to mix together, the person can match any single wavelength.

3

What is a grandmother cell?

A cell located in the IT lobe that recognizes specific objects and faces. ex. Jennifer Aniston

What does stereoblindness often result from?

A childhood visual disorder such as a strabismus, in which the two eyes are misaligned.

What is the difference between metrical and nonmetrical depth cues?

A metrical depth cue provides precise, quantitative information about distance from the observer, while a nonmetrical depth cue only provides information about relative depth ordering, not depth magnitude.

What is the difference between a monocular depth cue and a binocular depth cue?

A monocular depth cue is available when the world is viewed with only one eye. A binocular depth cue requires information from both eyes.

What is the basic idea behind a structural description, and how do structural description theories improve on template theories?

A structural description describes the structure of an object in terms of its constituent parts and the relationships between those parts. The advantage over templates is that a single structural description can potentially match a large number of slightly different shapes. However, each figure would require a different template in a naive template theory.

What are basic, subordinate, and superordinate categories?

A subordinate level category is one that is quite specific, referring to a relatively small number of objects (e.g., Camaro). A superordinate level category, on the other hand, is much more general. Superordinate categories are often defined by functional or conceptual, rather than shape-based, qualities (e.g., vehicle). Basic level categories are in-between (e.g., car).

How are the Gestalt grouping principles related to texture segmentation?

A texture is really just a collection of many perceptual elements that are similar to each other and arranged closely together. Therefore, stating that areas of an image with different textures are segmented from each other (the definition of texture segmentation) is really the same thing as saying that areas of an image in which elements are similar to each other and/or close together group together.

What are ambiguous figures, and how do they relate to the perception by committee metaphor?

Ambiguous figures, such as the Necker cube, have more than one valid interpretation. Our perceptual committees settle on one and only one of these interpretations at a time, but the interpretation may "flip" from time to time.

Why is it important to include the phrase "all else being equal" when stating the Gestalt grouping principles?

Because we can only be absolutely sure that a principle will adequately predict how elements will be grouped if no other principles can also be applied.

What do nonaccidental features tell us about a scene?

Certain arrangements of edges can be interpreted as providing important information about segmenting objects in a scene, provided we are seeing the edges from a nonaccidental viewpoint. For example, a "T-junction" (a place where one edge abuts another straight edge in a T-like fashion; the arrow in the figure at left points to a T-junction) strongly indicates that the two edges are parts of different objects.

In what way are color-anomalous individuals and cone monochromats color-blind?

Color-anomalous individuals are people who can make discriminations based on wavelength, but the discriminations are different from the normal. Cone monochromats are individuals with only one cone type, and therefore they cannot discriminate different colors, meaning that they are truly color-blind.

How are convergence and divergence important to depth perception?

Convergence refers to turning your eyes inward while divergence refers to turning your eyes outward. These two types of eye movements are important because they allow the observer to place the two images of a feature in the world on corresponding locations in the two retinal images (typically on the fovea of each eye). They both reduce the disparity of that feature to zero, or nearly zero.

What evidence is there that the visual system starts with large objects and then divides them into smaller parts, rather than processing scenes the other way around?

Evidence for this proposition comes from the global superiority effect. In displays like those at the left (a giant E made up of Gs), it was found that identifying the small (local) letters took longer than identifying the larger (global) letter, indicating that the global information is more readily available than the local information.

What is low-level vision?

Extracting basic features from an image

_____ is where middle vision is carried out and illusory contours are processed.

Extrastriate cortex

What is the face inversion effect, and how does it relate to the special mechanisms thought to be operating when we recognize faces?

Faces are more difficult than other objects to recognize when inverted. Researchers have proposed that when faces are inverted, the special processes that are usually brought to bear in recognizing faces cannot operate, so we are forced to rely on our "normal" object recognition processes, which are not as efficient for subordinate-level objects, like faces.

What is a geon?

Geons are "geometric ions" and are the three-dimensional building blocks of structural descriptions in Biederman's recognition-by-components theory of object recognition. The defining quality of geons is that they are discriminable from each other based on non-accidental features, so they should be easily recognizable from any viewpoint.

The end-stage processing of face and object recognition is carried out in the _____ lobe.

IT; inferotemporal lobe

What happens if you shine "blue" and "yellow" lights on the same patch of paper?

If you shine "blue" and "yellow" lights on the same patch of paper, the wavelengths will add, producing an additive color mixture. Since "yellow" is equivalent to a mix of long and medium wavelengths, and "blue" consists of short wavelengths, the two lights will produce a mixture of short, medium, and long wavelengths. The resulting mixture will therefore look "white."

What is binocular rivalry?

It is the competition between the two eyes for control of visual perception, which is evident when completely different stimuli are presented to the two eyes.

What kind of movement does motion parallax depend on? Explain.

It depends on either object movement or head movement. During either type of motion, closer objects move faster across the visual field than farther objects, allowing one to determine the depth of objects relative to each other.

When does one view cyclopean stimuli?

It happens when looking at random dot stereograms. These are stimuli that are defined by binocular disparity alone.

How might color vision aid animals in finding food?

It helps animals locate and identify food that would not otherwise stand out for a creature with monochromatic vision. For instance, red berries in a green bush are much easier to locate with color vision, and it is also easier to tell whether the berries are ripe or not if you can perceive the difference between green and red.

What is a unique hue?

It is a color that can be described with only a single color term.

What is a pictorial depth cue?

It is a cue to distance or depth used by artists to depict three-dimensional depth in two-dimensional pictures.

Explain what a texture gradient is.

It is a depth cue based on the geometric fact that items of the same size form smaller images when they are farther away. Thus, an array of items that change in size across the image will appear to form a surface in depth. It is a combination of the relative height and relative size depth cues.

What kind of information does aerial perspective provide about the stimulus?

It is a depth cue that is based on the implicit understanding that light is scattered by the atmosphere. More light is scattered when you look through more atmosphere. Thus, more distant objects are subject to more scatter and appear fainter, bluer, and less distinct. It provides information about the relative distance of objects from the observer.

What is a stereoscope?

It is a device for presenting one image to one eye and another image to the other eye. Once these two images are fused by the observer, they create a single three-dimensional image with a strong impression of depth.

What is a critical period and why is it important for stereo vision?

It is a duration of time during development in which an organism is particularly susceptible to developmental change. In terms of stereo vision, if an observer does not receive the correct stimulation during their critical period they will not be able to see in stereo later in life. Disorders such as strabismus (a misalignment of the two eyes) can cause a lack of the correct stimulation during the critical period and lead to stereoblindness.

What is stereoacuity?

It is a measure of how accurate an observer's stereo vision is, defined as the smallest binocular disparity that the observer can detect.

What is a double-opponent cell?

It is a neuron whose output is based on a difference between sets of cones and is more complicated than a cone-opponent cell. In double-opponent cells, the center region is excited by one cone type and inhibited by another (e.g., R+/G-) and the surround has the opposite arrangement (e.g., G+/R-).

What is the idea behind positivism?

It is a philosophical position arguing that all you really have to go on is the evidence of your senses, so the world might be nothing more than an elaborate hallucination.

What is a random dot stereogram?

It is a stereogram made of a large number of randomly placed dots. The random dot stereogram contains no monocular cues to depth.

Why is the LGN is important in color perception?

It is a structure in the thalamus of the brain that receives input from retinal ganglion cells and has input and output connections to the visual cortex. Some of its cells are maximally stimulated by spots of light in a center-surround architecture, which is critical to color perception. The LGN contains cone-opponent cells that essentially subtract one type of cone input from another in a center-surround manner.

When is free fusion used?

It is a technique of converging or diverging the eyes in order to view a stereogram without a stereoscope.

Describe the idea of color space.

It is a three-dimensional representation of all possible colors, which are based on the three cone types.

What is a negative afterimage?

It is a type of afterimage whose polarity is the opposite of the original stimulus. For instance, light stimuli produce dark negative afterimages. Colors are complementary: red produces green afterimages and yellow produces blue afterimages. The negativity of the afterimages arises from the cone-opponent cells.

What is achromatopsia?

It is an inability to perceive colors that is caused by damage to the central nervous system.

What is the advantage of binocular summation?

It is that detecting a stimulus can be done with two eyes, as opposed to just one, and so this yields more information about the stimulus.

What is a vanishing point?

It is the apparent point at which parallel lines receding in depth converge. Vanishing points are often used in paintings and drawings to add a sense of realism and depth.

What is cultural relativism?

It is the idea that basic perceptual experiences such as color perception may be determined in part by the cultural environment.

When does suppression occur in vision?

It is the inhibition of an unwanted image and typically occurs in people with strabismus. In those cases, the turned eye which has an object projecting to a nonfoveal area is suppressed so as not to interfere with the other eye in which the object of interest falls on the fovea.

Define the correspondence problem.

It is the problem of figuring out which bit of the image in the left eye should be matched with which bit in the right eye. It must be solved by the visual system before stereo depth can be perceived.

What is the horopter?

It is the set of points in the environment that have the same disparity as the object currently fixated (disparity 0).

What is uncrossed disparity?

It is the sign of disparity created by objects behind the plane of fixation. Images of objects that are located behind the horopter will appear to be displaced to the right in the right eye, and to the left in the left eye.

What is crossed disparity?

It is the sign of disparity created by objects in front of the plane of fixation (the horopter). Images of objects that are located in front of the horopter will appear to be displaced to the left in the right eye, and to the right in the left eye.

Describe the idea of color constancy.

It is the tendency of a surface to appear to be the same color under a fairly wide range of illuminants.

Describe the method of "hue cancellation."

It is used to demonstrate opponent color theory. In this method, the experimenter might start with a light that appears to be a yellowish green. The experimenter then cancels the yellowness by adding its opponent color, blue. The experimenter then measures the amount of blue light needed to remove all traces of yellow.

What is a subtractive color mixture?

It is when one source of illumination is subtracted from another, as when two color filters are placed in front of a light source or when pigments are mixed. If pigments A and B mix, some of the light shining on the surface will be subtracted by A, and some by B. Only the remaining light that was not absorbed by either A or B contributes to the perception of color.

What is an additive color mixture?

It is when two sources of illumination combine to make a new color, as when mixing lights. If light A and light B are both reflected from a surface to the eye, the colors of those two lights add together.

What is strabismus?

It refers to the misalignment of the two eyes such that a single object in space is imaged on the fovea of one eye and a nonfoveal area of the other (turned) eye.

In what sense does the Bayesian approach take into account past experience? Explain.

It states that prior knowledge influences one's estimates of the probability of a current event. In the case of vision, since the retinal images formed on the two retinas could be a result of an infinite number of scenes, this approach helps to narrow down the possible choices to the ones that are the most likely, based on past experiences.

What is the trichromatic theory of color vision?

It was developed in the nineteenth century by both Young and Helmholtz, -proposes that any light is defined in our visual system by the relationships between a set of three numbers, which we now know to be the outputs of the three cone types.

Process of vision:

LGN-->Straite Cortex (V1)--> Extrastriate Cortex--> Either dorsal or ventral pathway.

Describe two physical constraints that make constancy possible.

Luminance tends to change abruptly between surfaces and gradually within surfaces, so surface boundaries are an important physical constraint for achieving constancy. The fact that shadow boundaries change the brightness and not the chromatic properties of a surface is also an important physical constraint for constancy.

Why is face recognition thought to be accomplished via different mechanisms than object recognition?

Most objects require considerably more time to recognize at the subordinate than at the basic level. However, recognition of individual faces, which is a subordinate-level task, is a very fast process—so fast that many researchers believe the visual system must use "special" mechanisms to recognize faces. Also, face recognition and object recognition can be doubly dissociated—people with object agnosia can recognize faces but not objects whereas people with prosopagnosia can recognize objects but not faces.

What do we mean when we say that objects can be recognized at different levels?

Object recognition is essentially a categorization process. Identifying an object means deciding what category the object belongs in. Most objects actually have a number of categories that they could be placed in. The level of recognition refers to the specificity of the category you use when identifying an object. For instance, you can recognize a chair as a "barber chair," "chair," or "furniture," depending on what category you are using.

Why can such theories, such as the naive template theory, be rejected as a complete theory of object recognition?

One of the most important problems is that it seems unlikely that we have enough brain capacity to store templates to match every single object in every single viewpoint that we are likely to encounter in our lives.

Tong (1998) used binocular rivalry to test brain responses by presenting a house to one eye and a face to the other. The person perceived a house, activity in the ______ increased.

PPA

What is prosopagnosia, and what does it say about special face recognition processes?

Prosopagnosia is a neuropsychological disorder in which people cannot recognize faces, although they can recognize other objects normally. It is due to damage in fusiform face area (FFA) of the brain where special face recognition processes are carried out.

Opponent cells (retinal ganglion cells and lateral geniculate nucleus) cells differ from double opponent cells in the primary visual cortex (V1) in that ______.

RG and LGN cells might be excited by one color (for example, red) in the center and inhibited by its complement (green) in the surround; a V1 cell might be excited by red and inhibited by green in its center, and excited by green and inhibited by red in its surround.

What are some of the major challenges when recognizing objects?

Recognizing objects regardless of the viewpoint you happen to see them in AND how to separate out the contours of objects from the background and from other objects that might be in front of them.

What is an example of a unique hue?

Red is an example of a unique hue, as opposed to orange, which can be described as a compound (reddish yellow).

What is the notion of relatability?

Relatability is the notion that line segments on either side of an occluding surface will look like they are part of a single object if they can be connected by a smooth curve that only bends once.

How do some birds and reptiles achieve color vision without having photoreceptors with different spectral sensitivities?

Some animals have evolved a system for color vision in which small droplets of colored oils sit on top of photoreceptors and filter the light coming into them. This has the same function as having photoreceptors with different spectral sensitivities.

Why can't we apply a simple rule like "homogeneous areas belong to the same object" in order to find an object's contours?

Sometimes we perceive object contours even in areas of an image where there is no physical difference between the object and its background.

An example of a negative afterimage.

Staring at a green, black, and yellow American flag then looking away at a white screen to see the original American flag with it's original Red, White, and Blue coloring.

What does the trichromatic theory of color vision tell us about color perception?

The color of any light is defined in our visual system by the relationships between the outputs of the three cone types.

What is the principle of univariance?

The fact that an infinite set of different wavelength-intensity combinations can elicit exactly the same response from a single type of photoreceptor. One photoreceptor type cannot make accurate color discriminations by itself.

What is a naive template theory?

The formal definition of a template is complicated, but template theories essentially follow a "lock and key" principle. The perceived image is the key, and the template is the lock. The naive template approach says that we store templates for all the images of all the objects we have ever seen. When we perceive an object that we want to recognize, we try to match this perception to all the templates stored in memory until we find a lock in which the key fits exactly.

Why do we sometimes see optical illusions?

The images that fall on our retinas are ambiguous since there are a number of spatial layouts that could give rise to the same images. Therefore, our visual systems assess the depth cues available and make a guess as to the true spatial layout. In some cases, the guesses our visual systems make are wrong, leading to optical illusions.

What is stereoblindness?

The inability to make use of binocular disparity as a depth cue.

What is the Vieth-Müller circle?

The location of objects whose images fall on geometrically corresponding points in the two retinas. If life were simple, this circle would be the horopter, but life is not simple.

What is figure-ground assignment?

The process of determining that some regions of an image belong to the foreground object (figure) and other regions are part of the background (ground).

Describe the three types of cones in the human visual system and explain the differences between them.

The three types of cones in the human visual system are: S-cones, M-cones, and L-cones. They are all collectively responsible for discriminating between different colors. The S-cones are preferentially sensitive to short wavelengths (e.g., "blue"), the M-cones are preferentially sensitive to middle wavelengths (e.g., "green"), and the L-cones are preferentially sensitive to long wavelengths (e.g., "red").

Why do metamers produce the same perceived color?

They are different mixtures of wavelengths that nonetheless look identical. Even though the wavelength mixtures are different, they produce the same response from the cones in our visual system, which in turn causes the colors to appear identical.

Explain the concept of corresponding retinal points.

They are points on the retina of each eye where the monocular retinal images of a single object are formed at the same distance from the fovea in each eye. The two foveas are also corresponding points.

What are basic color terms?

They are single color words (e.g., "blue," not "sky blue"), used with high frequency, and have meanings that are agreed upon by speakers of a language.

Why is the notion of relatability important?

This concept is important because it describes the constraints our brains use to fill in edge information from objects that is missing due to occlusion.

How is camouflage related to grouping principles?

To camouflage yourself, you have to make your features group with the features present in your environment.

What is the fundamental goal of object recognition?

To match a perceived stimulus to a representation of a previously encountered object encoded in memory.

What is the basic idea behind the "perception by committee" metaphor?

Various parts of our visual system act like perceptual committees, considering which rules conflict and which agree in a given situation and eventually arriving at a single interpretation for the scene.

What does a color with zero saturation look like?

White

The case of Mr. I is a 50-year-old male who lost his color vision after a head injury. This case is evidence for _____.

a "color center" in the cortex

Which of the following is a general determinant of figure-ground segregation?

a lower region is more likely to be perceived as figure than ground.

Structuralists focused on ______, while Gestalt psychologists focused on the ____ picture.

basic perception; whole (all elements of a)

Which of the following is behavioral support for opponent-process theory?

color afterimages

Researcher Dortha Jameson is quoted in the text as saying "A blue bird would not be mistaken for a goldfinch if it were brought indoors. This supports the concept of _____.

color constancy

Corey looks at a flock of seagulls flying in one direction, when suddenly five birds start flying in another direction. He now perceives two groups of birds, because of the Gestalt principle of _______.

common fate.

One"grandmother" neuron studied by Quirogi et al., responded preferentially to _______.

drawings of Halle Berry , Halle Berry dressed as Catwoman, and the words "Halle Berry" written on a screen .

Another name for foreground

figure

Another name for background

ground

An _____ contour is one that is perceived even though they are not present in the physical stimulus.

illusory (example. Kanisza triangle)

The ventral visual pathway goes to the __________ lobe.

inferotemporal (lower temporal)

Border ownership means that when figure-ground segregation occurs, the border between the figure and the background __________.

is perceived to be associated with the figure.

According to the ratio principle ______.

lightness constancy will occur as long as the ratio of light reflected from a white surface and a black surface remains constant.

In one reversible figure-ground study, Gibson and Peterson (1994) used an image that looked like a woman when upright but did not resemble anything when turned upside-down. The general finding was that ______.

meaningfulness of an image had a large effect on figure-ground segregation

What is high-level vision?

object recognition and scene understanding

Name three monocular depth cues.

occlusion, relative size, familiar size, relative height, texture gradients, linear perspective, aerial perspective, motion parallax, accommodation, or convergence.

The dorsal visual pathway goes to the __________ lobe

parietal

Early vision processes are carried out in the _______.

striate cortex

William Wundt is to _________ as Max Wertheimer is to __________.

structuralism; Gestalt psychology.

Jimmy looks at a picture of a submarine that has dents and bumps on it. When he turns the picture upside down, what he originally saw as dents now looks like bumps and vice-versa. This is due to _______.

the light-from-above heuristic.

Activity in the PPA is ___________.

the same for pictures of furnished and empty rooms.

Opponent process and trichromatic theory were reconciled by the discovery that _______.

there were three different cones receptors that responded to three different wavelengths of light, but retinal ganglion neurons and lateral geniculate neurons had opponent properties, with cells that were excited by one color but inhibited by its complement.

The rarest form of dichromatism is _____.

tritanopia.

A monkey with good color vision _______.

would have a better chance of survival than a color-blind monkey.