Final Exam Perception

the ability to detect a stimulus and, perhaps, to turn that detection into a private experience.

·       The act of giving meaning to a detected sensation.

The only things that exists is matter, and that all things, including mind and consciousness, are the results of interactions between bits of matter.

The science of defining quantitative relationships between physical and psychological (subjective) events.

The smallest detectable difference between two stimuli, or the minimum change in a stimulus that can be correctly judged as different from a reference stimulus; also known as difference threshold.

Minimum amount of stimulation necessary for a person to detect a stimulus 50% of the time.

Many stimuli, ranging from rarely to almost always perceivable, are presented one at a time.

Similar to the method of limits, but the participant controls the stimulus directly.

The participant assigns values according to perceived magnitudes of the stimuli.

The participant matches the intensity of a sensation in one sensory modality with the intensity of a sensation in another.

An internal threshold that is set by the observer.

A value that defines the ease with which an observer can tell the difference between the presence and absence of a stimulus or the difference between stimulus 1 and stimulus 2.

: A mathematical procedure by which any signal can be separated into component sine waves at different frequencies; combing these component sine waves will reproduce the original signal.

·       The number of cycles of a grating per degree of visual angle.

The junction between neurons that permits information transfer.

: A chemical substance used in neuronal communication at synapses.

 A technique that, using many electrodes on the scalp, measures electrical activity from populations of many neurons in the brain.

Variant of MRI. Measures localized patterns of brain activity. Activated neuron’s provoke increase blood flow, which can be quantified by measuring changes of oxygenated and deoxygenated blood to strong magnetic fields.

founder of psychophysics.

Energy that is redirected when it strikes a surface, usually back to its point origin.

Energy (light) that is taken up and is not transmitted at all.

Energy that is altered as it passes into another medium.

The watery fluid in the anterior chamber.

gel-like transparent fluid that fills the eye’s largest chamber (vitreous chamber), helps holds eye’s shape.

·       The dark circular opening at the center of the iris in the eye, where light enters the eye.

The colored part of the eye, a muscular diagraph, that regulates light entering the eye by expanding and contracting the pupil.

Inside the eye, which focuses light into the back of the eye.

: A light-sensitive membrane in the back of the eye that contains rods and cones. The lens focuses an image on the retina, which then sends signals to the brain through the optic nerve.

When light is focused in front of the retina and distant objects cannot be seen sharply; nearsightedness.

Literally “old sight”, severely diminished ability of the lens to accommodate due to advanced age.

Photoreceptors specialized for night vision.

Specialized daytime vision, fine visual acuity, and color.

2% total retinal area but 33% ganglion cells devoted to it.

Antagonistic interaction between adjacent regions.

The projection neurons of the vertebrate retina, conveying information from other retinal neurons to the rest of the brain.

Excited by light that falls on their center and inhibited by light that falls in their surround.

·       Inhibited when light falls in their center and excited when light falls in their surround.

small cells

large cells

The difference in illumination between a figure and its background.

The smallest spatial detail that can be resolved at 100% contrast; better in fovea, worse in periphery of vision.

Unit of measure expressing the size of an image on the retina.

Describes how spatial frequency and contrast interact to make a grating more or less visible.

In the thalamus.

Cells in each layer of LGN show an orderly representation of the retina.

Do not have well defined ON-OFF regions. Do have preference for orientations of stimulus. Properly oriented stimulus can be anywhere in RF to get strong response.

Receptive fields elongated (not circular). Simple relationship between RF layout and preferred stimulus. To get strong response, stimulus must be positioned exactly within RF.

A 1-mm block of striate cortex containing “all the machinery necessary to look after everything the visual cortex is responsible for, in a certain small part of the visual world.

: A reduction in response caused by prior or continuing stimulation.

·       A misalignment of the two eyes.

Reduced spatial vision in an otherwise healthy eye.

jaragon of the field to stan for any cell that seems to be selectively responsive to one specific object.

Failure to recognize objects despite the ability to see them.

A process that carries out a computation one neural step after another, without the need for feedback from a later stage to an earlier stage.

·       A contour that is perceived even though nothing changes from one side of the contour to the other.

The whole is greater than the sum of its parts.

 Items will group if they appear to be part of the same larger region.

Elements that change at the same time tend to group together.

: A formal, mathematical system that combines information about the current stimulus with prior knowledge about the world

An inability to recognize faces.

·       If multiple invocations can safely run concurrently on multiple processors.

In Biederman’s recognitions, which holds that objects are recognized by the identities and relationships of their component parts.

A description of an object in terms of the nature of its constituent parts and the relationships between those parts.

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 color discriminations based on wavelength.

Stimuli that are physically different but produce the same perception.

3

Conveys information about the color of a broad area. Example the cells are most excited by red and not green.

Ewald Hering. One member of the color pair suppresses the other color. For example, we do see yellowish-greens and reddish yellows, but we never see reddish-green or yellow-blue color hues.

3 opponent channels, each comprising an opposing color pair: red versus green, blue versus yellow, and black versus white.

The visual cortex

An individual who suffers from color blindness that is due to the absence of M-cones.

A mixture of lights. If light A and Light B are both reflected from a surface to the eye, in the perception of color the effects of those two lights add together.

A mixture of pigments. 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 remainder will contribute to the perception of color.

Has no cones of any type; truly color-blind and very visually impaired in bright light.

A color perception effect in which the color of one region induces the opponent color in a neighboring region.

The tendency of a surface to appear the same color under a fairly wide range of illuminants.

A color perception effect in which two colors bleed into each other, each taking on some of the chromatic quality of the other.

1. Light is differentially absorbed by three photopigments in the cones. 2. Differences are taken between cone types, creating cone-opponent mechanisms, important for wavelength discrimination.  3. Further recombination of the signals creates color-opponent processes that support the color-opponent nature of color appearance.

The combination of signals from each eye in ways that make performance on many tasks better with both eyes than with either eye alone.

·       The differences between the two retinal images of the same scene.

A depth cue that provides quantitative information about distance in the third dimension.

A depth cue that provides information about the depth order but not depth magnitude.

: A depth cue based on the geometric fact that items of the same size form smaller, closer spaced images the farther away they get.

A cue based on knowledge of the typical size of objects.

The apparent point at which parallel lines receding in depth converge.

The ability of the two eyes to turn inward, often used to focus on nearer objects.

Lines that are parallel in the three-dimensional world will appear to converge in a two-dimensional image as they extend into the distance.

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

Images closer to the observer move faster across the visual filed than images farther away.

The process by which the eye changes its focus (in which the lens gets fatter as gaze is directed toward nearer objects).

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

A stereogram made of a large number of randomly places dots.

In binocular vision, the problem of figuring out which bit of the image in the left eye should be matches with which bit in the right eye.

The ability to use binocular disparity as a cue to depth.

Any of the very large set of selective processes in the brain.

A stimulus that might indicate where or what a subsequent stimulus will be.

In visual search, any stimulus other than the target.

Search for a target defined by a single attribute, such as a salient color or orientation.

The vividness of a stimulus relative to its neighbors.

In visual attention, referring to the processing of multiple stimuli at the same time.