Chapter 4: Sensation and Perception

Sensation

The process of converting sensory information into our perception of the world through our senses.

Psychophysics

The study of the relationship between physical stimuli and the sensations and perceptions they evoke.

Thresholds

The minimum amount of stimulation required for a sensory receptor to detect a stimulus.

Absolute threshold

The minimum amount of stimulus energy that a person can detect.

Just noticeable difference (JND)

The minimum difference in stimulation that is just noticeable.

Weber's Law

The JND is a fraction of the original stimulus intensity.

Perception

The subjective interpretation and understanding of sensory information.

Qualia

The subjective and individual experience of perception.

Visual System

The sensory system responsible for processing visual information.

Retina

The light-sensitive tissue at the back of the eye that contains photoreceptor cells.

Rods

Photoreceptor cells in the retina that are highly sensitive to light and enable vision in low-light conditions.

Cones

Photoreceptor cells in the retina that are responsible for color vision and visual acuity.

Auditory System

The sensory system responsible for processing sound information.

Sound Waves

Vibrations of molecules that travel through air and are detected by the auditory system.

Taste

The sensory system responsible for detecting and perceiving the chemical properties of substances.

Taste Buds

The sensory receptors for taste located on the tongue and in the mouth.

Primary Tastes

The basic taste sensations of sweet, sour, bitter, and salty.

Smell

The sensory system responsible for detecting and perceiving odors.

Olfactory System

The sensory system responsible for processing smell information.

Skin Senses

The sensory system responsible for detecting and perceiving physical stimuli on the skin, such as touch, temperature, and pain.

Optic Nerve

The structure at the back of the eye, made up of axons of the ganglion cells, that carries visual information to the brain for further processing.

Pinna

The outermost part of the ear, consisting of the pinna and the external auditory canal.

Pain

The sensation that warns an individual of damage to the body.

Taste Buds

Rounded bumps above the tongue's surface that contain the taste buds, the receptors for taste.

Parallel Processing

The simultaneous distribution of information across different neural pathways.

Perception

The process of organizing and interpreting sensory information so that it makes sense.

Perceptual Constancy

The recognition that objects are constant and unchanging even though sensory input about them is changing.

Perceptual Set

A predisposition or readiness to perceive something in a particular way.

Place Theory

Theory on how the inner ear registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane.

Retina

The multilayered, light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain.

Rods

The receptor cells in the retina that are sensitive to light but not very useful for color vision.

Selective Attention

The act of focusing on a specific aspect of experience while ignoring others.

Semicircular Canals

Three fluid-filled circular tubes in the inner ear containing the sensory receptors that detect head motion caused when an individual tilts or moves the head and/or the body.

Sensation

The process of receiving energy from stimuli in our internal or external environment and transforming this energy into action potentials.

Sensory Adaptation

A change in the responsiveness of the sensory system to the average level of stimulation.

Sensory Receptors

Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain.

Signal Detection Theory

An approach to perception that focuses on decision making about stimuli under conditions of uncertainty.

Subliminal Perception

The detection of information below the level of conscious awareness.

Thermoreceptors

Sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body's temperature at 37 degrees Celsius.

Top-Down Processing

The operation in sensation and perception, launched by cognitive processing at the brain's higher levels, that allows the organism to sense what is happening and to apply that framework to information from the world.

Transduction

The process by which a specialized receptor cell converts energy from an external stimulus (e.g., light, sound, heat) to an internal electrical signal (action potentials).

Trichromatic Theory

Theory stating that color perception is produced by three types of cone receptors in the retina that are particularly sensitive to different, but overlapping, ranges of wavelengths.

Vestibular Sense

Sense that provides information about balance and movement.

Volley Principle

Modification of frequency theory stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses.

Weber's Law

The principle that two stimuli must differ by a constant minimum percentage (rather than a constant amount) to be perceived as different.