Introduction to Sensation and Perception
Sensation and Perception
Definitions
Sensation: The elementary component of an experience, such as light and dark, bitter taste, and changes in temperature.
Perception: The collection of processes used to arrive at a meaningful interpretation of sensations.
The Five Senses
- Touch
- Sight
- Smell
- Taste
- Hearing
Psychophysics
Psychophysics: A field in psychology in which researchers search for ways to describe the transition from a physical stimulus to the psychological experience of the stimulus.
Transduction: The process by which external messages are translated into the internal language of the brain.
Absolute Threshold: The intensity level at which people can detect the presence of a stimulus 50% of the time.
Signal Detection: A technique used to determine the ability of someone to detect the presence of a stimulus.
Difference Threshold: The smallest detectable difference in the magnitude of two stimuli.
Weber’s Law: The ability to notice a difference in the magnitude of two stimuli is a constant proportion of the size of the standard stimuli.
Sensory Adaptation: The tendency of sensory systems to reduce sensitivity to a stimulus source that remains constant.
Vision
Light and the Eye
Light: The small part of the electromagnetic spectrum that is processed by the visual system.
Hue: The dimension of light that produces color.
Brightness: The aspect of the visual experience that changes with light intensity.
Accommodation: In vision, the process through which the lens changes its shape temporarily to help focus light on the retina.
Rods: Photoreceptors that transduce light energy into neural messages; these visual receptors are highly sensitive and are active in dim light.
Cones: Photoreceptors that transduce light energy into neural messages; they operate best when light levels are high, and they are primarily responsible for the ability to sense color and fine detail.
Blind Spot: The point where the optic nerve leaves the back of the eye.
Receptive Field: In vision, the portion of the retina that, when stimulated, causes the activity of higher-order neurons to change.
Dark Adaptation: The process through which the eyes adjust to dim light.
Color Vision
Trichromatic Theory: A theory of color vision proposing that color information is extracted by comparing the relative activations of three different types of cone receptors.
Perceptual Organization
Bottom-Up Processing: Processing that is controlled by the physical message delivered to the senses.
Top-Down Processing: Processing that is controlled by one’s beliefs and expectations about how the world is organized.
Gestalt Principles of Organization: Organizing principles of perception proposed by Gestalt psychologists. These principles include the laws of proximity, similarity, closure, continuation, and common fate.
Recognition by Components: The idea proposed by Biederman that people recognize objects perceptually via smaller components called geons.
Geons: Simple geometrical forms; short for “geometrical icons.”
Depth Perception
Monocular Depth Cues: Depth cues that require input from only one eye. Includes relative size, overlap, linear perspective, shading, and haze.
Binocular Depth Cues: Depth cues that depend on comparisons between the two eyes.
Convergence: A depth cue based on the extent to which the two eyes move inward, or converge, when looking at an object.
Motion Perception
Phi Phenomenon: An illusion of movement that occurs when stationary lights are flashed in succession.
Perceptual Constancies and Illusions
Perceptual Constancy: Perceiving the properties of an object to remain the same even though the physical properties of the sensory message are changing.
Perceptual Illusions: Inappropriate interpretations of physical reality. Perceptual illusions often occur as a result of the brain’s using otherwise adaptive organizing principles.
Hearing
Sound: The physical message delivered to the auditory system.
Pitch: The psychological experience that results from the auditory processing of a particular frequency of sound. Frequency is measured in hertz (Hz).
Intensity: Pressure amplitude; psychologically, changes in intensity are experienced as changes in loudness. Wave amplitude is measured in decibels (dB).
Theories of Pitch Perception
Place Theory: The idea that the location of auditory receptor cells activated by movement of the basilar membrane underlies the perception of pitch.
Frequency Theory: The idea that pitch perception is determined partly by the frequency of neural impulses traveling up the auditory pathway.
Other Senses
Touch
Bottom-Up Processing: Controlled by the physical message delivered to the senses.
Top-Down Processing: Controlled by one’s beliefs and expectations.
Cold Fibers: Neurons that respond to a cooling of the skin by increasing the production of neural impulses.
Warm Fibers: Neurons that respond vigorously when the temperature of the skin increases.
Pain
Pain: An adaptive response by the body to any stimulus that is intense enough to cause tissue damage.
Nociceptors: Neurons that respond to extreme heat, severe pressure, or internal damage such as inflammation.
Gate-Control Theory: The idea that neural impulses generated by pain receptors can be blocked, or gated, in the spinal cord by signals produced in the brain.
The Pain Pathway: Site of injury, spinal cord, brainstem, cerebrum.
Kinesthesia and the Vestibular System
Kinesthesia: In perception, the ability to sense the position and movement of one’s body parts.
Vestibular System: The receptor system that responds to movement, acceleration, and changes in upright posture.
Part of the Ear!: Vestibular sacs in the semicircular canals.