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Sensation and Perception

Sensation

  • Definition: Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Perception

  • Definition: Perception is the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Continuous Process of Sensation and Perception

  • Sensation and perception are interconnected and constitute a continuous process.

Overview of the Sensory Experience

  • How do we see the world?

    • Examples of perceptual phenomena:

    • Illusion of the subway

    • Breathing dots

    • What color is the dress?

    • Spinning dancer

Basic Concepts of Sensation and Perception

Processing Methods

  • Sensation and perception can be analyzed through two processing methods:

    • Bottom-up Processing:

    • Definition: Analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information.

    • Top-down Processing:

    • Definition: Information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

    • Perception is influenced by whether one primarily relies on external sensory information (bottom-up) or internal prior expectations (top-down).

Selective Attention

  • Definition: The focusing of conscious awareness on a particular stimulus.

Inattentional Blindness

  • Definition: Failing to see visible objects when our attention is directed elsewhere.

Change Blindness

  • Definition: Failing to notice changes in the environment.

Transduction

  • Definition: Conversion of one form of energy into another; in sensation, it refers to the transforming of stimulus energies (sights, sounds, and smells) into neural impulses our brains can interpret.

Psychophysics

  • Definition: The study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.

Thresholds

Absolute Threshold

  • Definition: The minimum stimulation necessary to detect a particular stimulus 50% of the time.

Signal Detection Theory

  • Definition: A theory that predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). It assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and alertness.

Subliminal Stimuli

  • Definition: Stimuli that are below one's absolute threshold for conscious awareness.

Priming

  • Definition: The activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.

Difference Threshold

  • Definition: The minimum difference between two stimuli required for detection 50 percent of the time, also known as just noticeable difference (jnd).

    • Example: If 50 ounces is raised by 1 ounce, the jnd is noticeable; if 100 ounces is raised by 2 ounces, the same holds true.

Weber’s Law

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

Sensory Adaptation

  • Definition: Diminished sensitivity as a consequence of constant stimulation. Sensory adaptation informs about environmental changes while allowing the body to ignore constant information that is not changing.

Perceptual Set

  • Definition: A mental disposition to perceive one thing and not another, influenced by expectations, context, emotion, and motivations.

Extrasensory Perception (ESP)

  • Definition: The controversial claim that perception can occur apart from sensory input, including abilities such as telepathy, clairvoyance, and precognition.

Parapsychology

  • Definition: The study of paranormal phenomena, including ESP and psychokinesis.

Light and Color Perception

Wavelength

  • Definition: The distance from the peak of one light or sound wave to the peak of the next; electromagnetic wavelengths vary greatly.

Hue

  • Definition: The dimension of color determined by the wavelength of light; known commonly as color names (e.g., blue, green).

Intensity

  • Definition: The amount of energy in a light or sound wave, perceived as brightness or loudness, determined by the wave’s amplitude.

Eye Anatomy

Pupil

  • Definition: The adjustable opening in the center of the eye through which light enters.

Iris

  • Definition: A ring of muscle tissue that forms the colored portion of the eye and controls the size of the pupil opening.

Lens

  • Definition: The transparent structure behind the pupil that changes shape to help focus images on the retina.

Retina

  • Definition: The light-sensitive inner surface of the eye, containing receptor rods and cones, and layers of neurons that begin processing visual information.

Accommodation

  • Definition: The process by which the eye’s lens changes shape to focus near or far objects on the retina.

Rods and Cones

  • Rods: Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision when cones don’t respond.

  • Cones: Retinal receptor cells concentrated in the center of the retina; function in daylight or well-lit conditions, detect fine detail, and give rise to color sensations.

Optic Nerve

  • Definition: The nerve that carries neural impulses from the eye to the brain.

Blind Spot

  • Definition: The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.

Fovea

  • Definition: The central focal point in the retina where the eye's cones cluster, responsible for sharp central vision.

Visual Processing

Feature Detectors

  • Definition: Nerve cells in the brain that respond to specific features of stimuli, such as shape, angle, or movement.

Parallel Processing

  • Definition: The processing of many aspects of a problem simultaneously; the brain’s natural mode of information processing for many functions, including vision, and contrasts with step-by-step (serial) processing.

Color Vision Theories

Young-Helmholtz Trichromatic (Three-Color) Theory

  • Definition: The theory that the retina contains three different color receptors (sensitive to red, green, and blue), which, when stimulated in combination, can produce the perception of any color.

Opponent-Process Theory

  • Definition: The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. This explains phenomena such as afterimages.

Gestalt Principles

Gestalt

  • Definition: An organized whole; Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.

Figure-Ground Relationship

  • Definition: The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).

Grouping

  • Definition: The perceptual tendency to organize stimuli into coherent groups.

Depth Perception

Depth Perception

  • Definition: The ability to see objects in three dimensions although the images that strike the retina are two-dimensional, enabling distance judgment.

Visual Cliff

  • Definition: A laboratory device for testing depth perception in infants and young animals.

Binocular Cues

  • Definition: Depth cues, such as retinal disparity, that depend on the use of two eyes.

Retinal Disparity

  • Definition: A binocular cue for perceiving depth; when comparing images from the retinas in two eyes, the brain computes distance. Greater disparity between two images indicates a closer object.

Monocular Cues

  • Definition: Depth cues, such as interposition and linear perspective, available to either eye alone.

Motion Perception

Phi Phenomenon

  • Definition: An illusion of movement created when two or more adjacent lights blink on and off in succession.

Perceptual Constancy

Perceptual Constancy

  • Definition: The ability to perceive objects as unchanging despite changes in illumination and retinal images, maintaining perceptions of consistent shapes, sizes, lightness, and color.

Color Constancy

  • Definition: The perception of familiar objects as having consistent color, even if changing illumination alters wavelengths reflected by the object.

Perceptual Adaptation

  • Definition: The ability to adjust to an artificially displaced or inverted visual field.

Auditory Perception

Audition

  • Definition: The sense or act of hearing.

Frequency

  • Definition: The number of complete wavelengths that pass a point in a given time (i.e., per second).

Pitch

  • Definition: A tone's experienced highness or lowness, which depends on frequency.

Middle Ear

  • Definition: The chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window.

Cochlea

  • Definition: A coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through trigger nerve impulses.

Inner Ear

  • Definition: The innermost part of the ear; includes the cochlea, semicircular canals, and vestibular sacs.

Hearing Loss Types

  • Sensorineural Hearing Loss: Hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness.

  • Conduction Hearing Loss: Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Cochlear Implant

  • Definition: A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

Theories of Hearing

Place Theory

  • Definition: The theory linking pitch perception to the place where the cochlea’s membrane is stimulated.

Frequency Theory

  • Definition: The theory stating that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, enabling pitch sensing.

Gate-Control Theory

  • Definition: A theory that proposes the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain. The activity of pain signals traveling up small nerve fibers opens the gate, while larger fibers or information from the brain can close the gate.

Kinesthesia

Kinesthesia

  • Definition: The system for sensing the position and movement of individual body parts.

Vestibular Sense

Vestibular Sense

  • Definition: The sense of body movement and position, including the sense of balance.

Sensory Interaction

Sensory Interaction

  • Definition: The principle that one sense may influence another, as when the smell of food influences its taste.

Embodied Cognition

Embodied Cognition

  • Definition: In psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.