Terms for Modules 1.6A - 1.6B

Unit 1B - Sleep/Sensation/Perception

Sensation

The process by which sensory receptors and nervous system receive and respond to light, sound, odor, and taste, and transmit that information into the brain.

Absolute Threshold

The minimum stimulus energy needed to detect a particular stimulus 50% of the time, studied by Gustav Fechner.

Transduction

(TRANSLATION) The conversion of one form of energy into another. In sensation, the transforming of physical energy (sights, sounds, and smells) into neural impulses the brain interprets.

Just Noticeable Difference (JND) / Different Threshold

The minimum difference between two stimuli required for detection 50% of the time. That detectable difference increases with the size of the stimulus.

Sensory Adaptation

Reduced sensitivity as a consequence of constant stimulation; sensory receptors become less responsive to constant stimuli over time; nerve cells fire less frequently.

Weber’s Law

The principle that two stimuli must differ by a constant minimum % or proportion to the original intensity of the stimulus to be perceived as different, described by Ernst Weber.

Sesnory Interaction

The principle that one sense may influence another, like the smell of food influences its taste. It shows how our senses work together to create our overall perception of the world.

Synesthesia

(“Perceive Together”) A condition in which stimulation of one sense triggers an experience in another; two senses are sensed at the same time.

Vision

The sense that allows us to perceive light energy as color, shape, and movement; location of transduction: retina

Retina

The light-sensitive back inner surface of the eye, containing receptor rods and cones and layers of neurons that begin the processing of visual information (converts light into neural signals).

Blindspot

The area on the retina where the optic nerve leaves the eye, creating a “blind” spot because no receptor (light-sensitive) cells are located there to detect visual stimuli.

Incomplete Retinal Image

The brain’s ability to fill in missing parts of an image that the retina doesn’t fully capture.

Lens

The transparent structure behind the pupil that changes shape to help focus images (light rays) on the retina or help the eye properly refract light, enabling clear vision at different distances.

Accommodation

(1) Sensation + Perception: The process by which the eye’s lens changes shape to focus images of near/far objects on the retina, allowing for clear vision by adjusting the curvature of the lens.

(2) Development Psych: Adapting our current understanding to incorporate new information.

Nearsightedness (myopia)

A condition in which nearby objects are seen clearly, but distant objects are blurry because the eyeball is too long or the cornea is too curved, causing the lens to focus the image on a point in FRONT of the retina.

Farsightedness (hyperopia)

A condition in which distant objects are seen clearly, but close objects are blurry because the eyeball is too short or the cornea is too flat, causing the lens to focus the image on a point BEHIND the retina.

Fovea

The central focal point on the retina, around which the eye’s cones cluster. It’s responsible for sharp central vision and contains a high concentration of cone cells (no rods), enabling detailed and color vision.

Trichromatic Color Theory

The theory that the retina contains three different types of color receptors (sensitive to red, green, and blue), which, when stimulated in combination, the brain combines signals from these cones to produce the perception of any color.

Opponent Process Color Theory

The theory that opposing retinal processes (red-green, blue-yellow, white-black) enable color vision. Activation of one color in the pair inhibits the other, leading to the perception of color afterimages and certain aspects of color vision.

Cones (Blue, Red, Green—Role of Wavelengths)

Photoreceptor cells in the retina that are concentrated near the center of the retina and that function in daylight or in bright conditions. It detects fine detail and color (e.g. reading text).

Afterimages

Visual illusions that occur when overstimulated cones in the retina continue to send signals after a stimulus is removed, resulting in a brief perception of an inverted or complementary image.

Ganglion Cells (Opponent Process Rule)

Neurons in the retina that receive visual information from bipolar cells transmit it to the brain via the optic nerve and play a role in processing visual signals and relaying them to the brain for further interpretation.

Dichromatism (color vision deficiency)

A color vision deficiency in which one of the three cone types is missing results in difficulty distinguishing between certain colors, especially reds and greens.

Monochromatism (color vision deficiency)

A rare color vision deficiency where no cones function, resulting in an inability to perceive colors (black and white).

Prosopagnosia

(Face Blindness) A neurological disorder that causes difficulty recognizing faces; some experience this after a stroke or surgery has damaged their brain’s visual cortex.

Blindsight

A condition where people with damage to the visual cortex can respond to visual stimuli without consciously experiencing it; some visual processing can occur unconsciously.