psych ch3

Absolute threshold

Minimum stimulation needed to detect a stimulus 50% of the time.

Signal detection theory

Detecting stimuli depends on sensitivity, expectations, motivation, and alertness.

Difference threshold

Smallest detectable difference between two stimuli.

Weber's law

The detectable difference is a constant proportion of the original stimulus.

Stevens's power law

Perceived intensity changes according to a power function of stimulus intensity.

Sensory adaptation

Reduced sensitivity after constant exposure to a stimulus.

Wavelength

Distance between two successive peaks of a wave; determines perceived color.

Amplitude

Height or intensity of a wave; relates to perceived loudness.

Frequency

Number of wave cycles per second; measured in hertz.

Transduction

Conversion of physical stimulus energy into neural signals.

Accommodation

The eye's lens changes shape to focus images on the retina.

Nearsightedness

Myopia: nearby objects are clear; distant objects appear blurry.

Farsightedness

Hyperopia: distant objects are clearer; nearby objects appear blurry.

Retina

Light-sensitive layer at the back of the eye containing rods and cones.

Blindsight

Responding to visual stimuli without consciously experiencing sight.

Rods

Retinal receptors for dim light, peripheral vision, and black-and-white vision.

Cones

Retinal receptors responsible for color vision and fine detail in bright light.

Fovea

Central retinal area with the highest concentration of cones; sharpest vision.

Dark adaptation

Eyes gradually become more sensitive when moving from light to darkness.

Trichromatic theory

Color vision comes from three types of cones sensitive to red, green, and blue.

Additive mixtures

Combining colored lights; red, green, and blue produce white light.

Subtractive mixtures

Combining pigments or paints; more colors absorb more wavelengths.

Complementary colors

Pairs of colors that combine to produce white or neutral gray light.

Opponent-process theory

Color vision uses opposing pairs: red-green, blue-yellow, and black-white.

Hair cells

Tiny sensory receptors in the cochlea that convert vibrations into neural signals.

Nerve deafness

Sensorineural hearing loss caused by damage to hair cells or auditory nerves.

Conduction deafness

Hearing loss caused by problems transmitting sound through the outer or middle ear.

Place theory

Pitch depends on where the basilar membrane vibrates most strongly.

Frequency theory

Pitch is determined by how frequently auditory neurons fire.

Volley principle

Groups of neurons alternate firing to encode higher sound frequencies.

Sensation

Detection of physical energy by sensory receptors.

Perception

Organizing and interpreting sensory information to understand the world.

Bottom-up processing

Building perception from incoming sensory information.

Top-down processing

Using prior knowledge and expectations to interpret sensory information.

Perceptual set

A readiness to perceive something in a particular way based on expectations.

Contextual effect

Surrounding information influences how a stimulus is perceived.

Figure-and-ground principle

Separating an object of focus (figure) from its background (ground).

Closure

Filling in missing information to perceive a complete object.

Subjective contour

Perceiving edges or shapes that are not physically present.

Perceptual constancy

Recognizing objects as stable despite changes in sensory input.

Depth perception

Ability to perceive distance and three-dimensional space.

Retinal disparity

Difference between the images received by each eye; helps judge depth.

Linear perspective

Parallel lines appear to converge as they move farther away.

Interposition

When one object blocks another, the blocking object appears closer.