Sensation and Perception Exam 1 Vocabulary Flashcards

Vocabulary practice flashcards covering psychophysics, eye anatomy, photoreceptors, visual pathways, lateral inhibition, and Gestalt principles of perception.

Distal Stimulus

The real, physical object present in the external world.

Proximal Stimulus

The information collected by our sensory systems (sensation) representing the external object.

Perception

The process equal to sensation plus interpretation/existing knowledge.

Absolute Threshold

The smallest amount of intensity a person needs to detect a stimulus.

Difference Threshold

The smallest amount of difference a person needs to perceive two stimuli as different.

Weber's Law

The principle stating that the difference threshold ($\Delta I$) is directly proportional to the background intensity ($I$).

Response Expansion

A phenomenon in magnitude estimation where psychological magnitude increases faster than stimulus magnitude, as seen with electric shock ($n = 3.5$).

Response Compression

A phenomenon in magnitude estimation where psychological magnitude increases slower than stimulus magnitude, as seen with brightness ($n = 0.33$).

Circular 'Sphincter' Muscle

An iris muscle that rotates to contract the pupil.

Radial 'Dilator' Muscle

An iris muscle that folds to open up the pupil.

Presbyopia

A condition in which the near point occurs because the lens can no longer adjust for close objects.

Myopia

Nearsightedness, or the inability to see distant objects clearly.

Hyperopia

Farsightedness, or the inability to see nearby objects clearly.

Astigmatism

A visual defect where the lens focuses light differently (and incorrectly) in multiple planes.

Opsin

The large protein strand component of a visual pigment molecule.

Retinal

The light-sensitive molecule attached to opsin within a visual pigment molecule.

Rhodopsin

The visual pigment molecule found in rod photoreceptors with peak absorption at $498\,nm$.

Photopsin

The visual pigment molecules found in cone photoreceptors.

Photopic Vision

Vision under well-lit daylight conditions driven primarily by cone photoreceptors.

Scotopic Vision

Vision under low-light conditions driven exclusively by rod photoreceptors.

Mesopic Vision

Vision under intermediate light conditions involving both rods and cones.

Fovea

The central retina region spanning $3\text{ degrees}$ of visual field, populated mostly by cones, with low convergence ($6$), small receptive fields, high acuity, and low light sensitivity.

Periphery (Retina)

The outer region of the retina populated mostly by rods, featuring diffuse bipolar cells, high convergence ($120$), large receptive fields, low acuity, and high light sensitivity.

Macula

The region of the retina spanning $13\text{ degrees}$ of the visual field around the fovea.

Blind Spot

The area spanning $5\text{ degrees}$ of the visual field where optic nerve fibers exit the retina, lacking photoreceptors.

Lateral Inhibition

An inhibitory neural process across neighboring receptors or bipolar cells that enhances contrast at borders and lightness differences.

Hermann Grid

A visual illusion consisting of white intersections between dark squares, where gray spots appear at the intersections due to lateral inhibition.

Mach Bands

An optical illusion where lateral inhibition causes exaggerated contrast boundaries between adjacent shades of gray.

Visual Pathway

The neural route extending from visual fields through the eyes, optic chiasm, lateral geniculate nucleus (LGN), and optic radiation to the primary visual cortex.

Magnocellular Layers

Layers $1$ and $2$ of the lateral geniculate nucleus (LGN), connected to rods, which process movement, depth, and brightness changes.

Parvocellular Layers

Layers $3$, $4$, $5$, and $6$ of the lateral geniculate nucleus (LGN), connected to cones, which process color and fine details (form).

Retinotopic Map

An organized spatial mapping on visual structures like the LGN that corresponds point-by-point to receptor locations on the retina.

Feature Detectors

Cortical neurons classified into simple, complex, and end-stopped types that respond to specific features of visual stimuli.

Inverse Projection Problem

The challenge in perception where a given two-dimensional image on the retina can be generated by an infinite number of different three-dimensional objects.

Viewpoint Invariance

The ability to recognize an object regardless of the viewpoint or angle from which it is observed.

Pragnanz (Law of Simplicity)

A Gestalt principle stating that every stimulus pattern is perceived in such a way that the resulting structure is as simple as possible.

Law of Similarity

A Gestalt principle stating that similar things are grouped together.

Law of Good Continuation

A Gestalt principle stating that connected points resulting in straight or smooth curves belong together following the smoothest path.

Law of Proximity

A Gestalt principle stating that objects that are near to each other tend to be grouped together.

Law of Common Region

A Gestalt principle stating that elements located within the same region tend to be grouped together.

Uniform Connectedness

A Gestalt principle stating that a connected region of visual properties is perceived as a single unit.

Synchrony

A Gestalt principle stating that visual elements occurring at the same time are seen as belonging together.

Common Fate

A Gestalt principle stating that objects moving in the same direction are grouped together.

Figure-Ground Segregation

The perceptual process of determining what part of the environment is the figure so that it stands out from the background.

Border Ownership

The perceptual property wherein the contour separating figure from ground belongs to the figure.

Recognition-by-Components Theory

A theoretical framework stating that objects are recognized by volumetric features known as geons.

Geons

The $36$ basic volumetric component shapes (such as cylinders, rectangular solids, and pyramids) used to recognize all 3-D objects.

Discriminability (Geons)

The ability to distinguish individual geons from one another.

Principle of Componential Recovery

The principle stating that an object can be recognized as long as we can identify its constituent geons.