Chapter 5: Sensation and Perception

Cones

Retinal cells that respond to higher levels of light and result in color perception.

Rods

Retinal cells that respond to low levels of light and result in black-and-white perception.

Explain the concept of threshold. Distinguish between absolute threshold and difference threshold.

Absolute threshold is the minimum detectable amount of energy required to activate a sensory receptor. Difference threshold is the amount of energy change necessary for a sensory receptor to detect a change in stimulation.

Convergence

A cue of binocular depth perception; when a person views a nearby object, the eye muscles turn the eyes inward.

Sensory Adaptation

A decrease in sensitivity to a constant level of stimulation.

Binocular Disparity

A depth cue; because of the distance between the two eyes, each eye receives a slightly different retinal image.

Place Coding

A mechanism for encoding high-frequency auditory stimuli in which the frequency of the sound wave is encoded by the location of the hair cells along the basilar membrane.

Temporal Coding

A mechanism for encoding low-frequency auditory stimuli in which the firing rates of cochlear hair cells match the frequency of the sound wave.

Sound Wave

A pattern of changes in air pressure during a period of time; it produces the perception of a sound.

Signal Detection Theory (SDT)

A theory of perception based on the idea that the detection of a stimulus requires a judgment - it is not an all-or-nothing process.

Discuss gate control theory and the control of pain.

According to the gate control theory, pain perception involves both a painful stimulus and spinal cord processing of the signal. Ways to decrease pain include activating touch or other senses, mental distraction, and thinking pleasant thoughts.

Discuss the advantages and disadvantages of cochlear implants.

Cochlear implants directly stimulate the auditory nerve, correcting hearing loss caused by a lack of hair cells in the inner ear.

Object Constancy

Correctly perceiving objects as constant in their shape, size, color, and lightness, despite raw sensory data that could mislead perception.

Monocular Depth Cues

Cues of depth perception that are available to each eye alone.

Binocular Depth Cues

Cues of depth perception that arise from the fact that people have two eyes.

Describe how culture influences taste perception.

Cultural factors influence taste perception. Foods consumed by breastfeeding mothers influence taste preference in their offspring.

Define the five basic taste sensations.

Every taste experience is composed of a mixture of five basic qualities: sweet, sour, salty, bitter, and umami (savory).

Identify the Gestalt principles of perceptual organization.

Gestalt principles of perceptual organization describe innate brain processes that put information into organized wholes. The Gestalt perceptual groupings are proximity, similarity, continuity, closure, and illusory contours.

Audition

Hearing; the sense of sound perception.

Top-Down Processing

How knowledge, expectations, or past experiences shape the interpretation of sensory information.

Distinguish between monocular and binocular depth cues.

Monocular depth cues are available to each eye alone, while binocular depth cues arise from the fact that people have two eyes. Binocular and monocular depth cues permit the perception of depth from a two-dimensional retinal image. Visual illusions can arise when the eye receives conflicting evidence - for example, a size cue that does not agree with a distance cue.

Describe motion perception and object constancies.

Motion perception combines motion aftereffects and stroboscopic movement. Object constancies enable us to perceive images accurately even when the raw stimuli are incomplete.

Describe the neural pathway for smell.

Odorants are chemical particles, outside the body, that can be detected by smell receptors. Smell receptors are located in the olfactory epithelium, in the lining of the nose and nasal cavity. Of all the sense, olfaction has the most direct route to the brain. Smell is the only sense not processed via the thalamus. Smell receptors send signals to the olfactory bulb, just below the frontal lobes, for processing. Humans can discriminate between thousands of odors but have difficulty naming what they smell.

Distinguish between the two types of pain.

Pain receptors are located all over the body, but most pain is signaled by haptic receptors in the skin. Fast, myelinated fibers process information about sharp sudden pain. Slow, nonmyelinated fibers process chronic dull pain.

Bottom-Up Processing

Perception based on the physical features of the stimulus.

Vestibular Sense

Perception of balance determined by receptors in the inner ear.

Kinesthetic Sense

Perception of the positions in space and movements of our bodies and our limbs.

Explain the relationship between pheromones and smell.

Pheromones activate smell receptors but are not identified as odors. Pheromones motivate mating behaviors in nonhuman animals and may affect humans similarly.

Describe how color vision happens.

Rods permit night vision. Cones permit color vision and acuity. The human retina contains three types of cones. Each type responds best to one wavelength of light: long, medium, and short. Color blindness results from the absence of photopigments sensitive to short, medium, or long wavelengths.

Distinguish between sensation and perception.

Sensation is the detection of physical stimuli in the environment. Perception is our conscious experience of those stimuli.

Taste Buds

Sensory organs in the mouth that contain the receptors for taste.

Explain how thresholds are related to signal detection and sensory adaption.

Signal detection theory is about the subjective nature of detecting a stimulus. Sensory adaptation occurs when sensory receptors stop responding to unchanging stimuli. The brain integrates diverse neural inputs to produce stable representations.

Describe how sound waves are transduced into neural active in the ear.

Sound is created when sound waves travel through the auditory canal to the eardrum, producing vibrations in the cochlea, a fluid-filled canal in the inner ear. The sensory receptors for audition are hair cells. Hair cells bend when pressure waves build up in the fluid of the cochlea. The hair cells' movement activates neurons in the auditory nerve. The vestibular system allows us to maintain balance, when it receives signals from the semicircular canals in the inner ear.

Describe how the sense of touch is processed by the skin and brain.

Tactile stimulation gives rise to the sense of touch. Haptic receptors process information about temperature and pressure. Haptic receptors send signals to the thalamus, which projects to the primary somatosensory cortex (in the parietal lobe).

Explain the significance of temporal and place coding for auditory perception.

Temporal coding and place coding are responsible for the perception of pitch. Low-frequency sounds result from temporal coding. At higher frequencies, groups of hair cells must take turns firing. In place coding, the high-frequency sound waves are encoded by the location of the hair cells along the basilar membrane.

Olfactory Bulb

The brain center for smell, located below the frontal lobes.

Fovea

The center of the retina, where cones are densely packed.

Sensation

The detection of external stimuli and the transmission of this information to the brain.

Difference Threshold

The minimum amount of change required for a person to detect a difference between two stimuli.

Absolute Threshold

The minimum intensity of stimulation that must occur before you experience a sensation.

Transduction

The process by which sensory stimuli are converted to signals the brain can interpret.

Perception

The processing, organization, and interpretation of sensory signals.

Olfaction

The sense of smell.

Gustation

The sense of taste.

Retina

The thin inner surface of the back of the eyeball; it contains the sensory receptors that transduce light into neural signals.

Describe how sensory information is translated into meaningful stimuli.

Transduction is the process by which sensory stimuli are translated into signals the brain can interpret. Transduction occurs at sensory receptors, specialized cells in each sense organ. Sensory receptors send messages to the thalamus, which sends projections to cortical areas for perceptual processing.

Compare and contrast trichromatic and opponent-process theories of color vision.

Trichromatic theory explains how just three types of cones account for all of the colors we see. Opponent-process theory explains why we experience negative afterimages.

Explain how light is processed by the eyes and the brain.

Vision is our most important sense because it provides the most information about the world. Visual transduction occurs when light enters the eye and activates the photoreceptors (rods and cones).

Eardrum

A thin membrane that marks the beginning of the middle ear; sound waves cause it to vibrate.

Olfactory Epithelium

A thin later of tissue, within the nasal cavity, that contains the receptors for smell.

Haptic Sense

The sense of touch.