Chapter 5 Sensation and Perception - Full Chapter

Retinal Disparity

A binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

Convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object.

Cochlear Implant

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

Visual Cliff

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

Perceptual Set

A mental predisposition to perceive one thing and not another. Our experience creates schemata, mental representations of how we expect the world to be. Our schemata influence how we perceive the world. Schemata can create this predisposition to perceiving something in a certain way. For example, you may perceive a cloud being shaped like a heart around Valentine's Day.

Sensory receptors

A sensory nerve ending that responds to a stimulus in the environment of an organism

Trichromatic Theory (Young-Helmholtz Theory)

A theory of color vision. Hypothesizes that we have three types of cones in the retina: cones that detect the primary colors of light - blue, red, and green. These cones are activated in different combinations to produce all the colors of the visible spectrum. Even though this theory has some research support and makes sense intuitively, it cannot explain such visual phenomena as afterimages and color blindness. Most researchers agree that color vision is explained by a combination of the Trichromatic and Opponent-Process Theories.

Pitch

A tone's experienced highness or lowness; depends on frequency. Measured in Hertz (Hz)

Sound Shadow

An area of reduced sound intensity around the ear farther away from where a sound originates. Helps us localized sounds.

Phi Phenomenon

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

Visible Light

Color is perceived due to a combination of different factors: Light intensity: how much energy the light contains determines how bright the object appears. Light wavelength: the length of the light waves determines the particular hue we see. (We see different wavelengths within the visible light spectrum as different colors).

Sensory Adaptation

Decreasing responsiveness to stimuli due to constant stimulation. For example, we eventually stop receiving a persistent scent in a room. This happens in your sensory organs. Another example: You put a pen behind your ear and forget it is there after a while because you don't feel it anymore.

Gestalt Rules

Developed by a group of researchers from the early 20th century who described the principles that govern how we perceive groups of objects. (e.g., proximity, similarity, continuity, closure). Based on the observation that we normally perceive images as groups, not as isolated elements. This process is believed to be innate and inevitable.

Shape Constancy

Objects viewed from different angles will produce different shapes on our retinas, but we know the shape of an object remains constant. For example, the top of a coffee mug viewed from a certain angle will produce an elliptical image on our retinas, but we know the top is circular due to shape constancy.

Sensation

Occurs when one of our senses (sight, smell, hearing, touch, or taste) is activated by something in our environment. Occurs before the process of perception. The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

Sensorineural Hearing Loss/Nerve Deafness

Occurs when receptor (hair or cilia) cells in the cochlea or auditory nerves have been damaged, usually by loud noise. Most common form of hearing loss.

Bottom-Up Processing

Opposite of top-down processing. Instead of using our experience to perceive an object, we use only the features of the object itself to build a complete perception. Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. We start our perception at the bottom with the individual characteristics of the image and put all of those characteristics together into our final perception. Our minds build the picture from bottom up using basic characteristics.

Sensory Habituation (also called Perceptual Adaptation)

Our perception of sensations as partially determined by how focused we are on them. For example, no longer hearing traffic from the nearby freeway after having lived in a place for years. While sensory adaptation happens in the sensory organs, sensory habituation happens in the brain. People who have habituated to something (e.g., a sound, a smell) can still perceive it if directed to focus attention on it. If you have adapted to it anymore, you can't perceive it (e.g. the cold of the water after you have been in the pool for a while).

Perceptual Constancy

Perceiving objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change. Every object we see changes minutely from moment to moment due to our changing angle of vision, variations in light, and so on. This is our ability to maintain a constant perception of an object despite these changes.

Feature Detectors

Perception researchers Hubel and Weisel discovered that groups of neurons in the visual cortex respond to different types of visual images. The visual cortex has feature detectors for vertical lines, shapes, curves, angles, and motion, among others. What we perceive visually is a combination of these features.

Depth Cues

Researchers divide the cues that we use the perceive depth into two categories: Monocular cues - Depth cues that do not depend on having two eyes (e.g., linear perspective, interposition, shading, and texture gradient). Binocular cues - Cues that depend on having two eyes (e.g., retinal disparity and convergence).

Difference Threshold

Smallest amount of change (minimum amount of difference) needed in a stimulus before we detect a change 50% of the time.. Computed by Weber's law, named after psychophysicist Ernst Weber. The change needed is proportional to the original intensity of the stimulus. The more intense the stimulus is, the more it will need to change before we notice a difference. If someone raises the volume on your phone and you notice the increase in volume, that increase in volume is above the difference threshold. We experience this as a just noticeable difference (JND).

Conduction Hearing Loss/Conduction Deafness

Something goes wrong with the mechanical system of conducting the sound to the cochlea (in the ear canal, eardrum, hammer/anvil/stirrup, or oval window). Difficult to treat because there is no method yet found that will encourage the hair cells to regenerate. Less common form of hearing loss.

Subliminal Messages

Stimuli below our absolute threshold. Research does not support claim that subliminal messages affect our behaviors in overt ways.

Perceptual Adaptation

The ability to adjust to changed sensory input. In vision, the ability to adjust to an artificially displaced or even inverted visual field

Depth Perception

The ability to see objects in three dimensions although the images that strike the retina are two dimensional; allows us to judge distance.

Priming

The activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

Intensity

The amount of energy in a light or sound wave, which influences what we perceive as brightness or loudness, as determined by the wave's amplitude (height).

Perception

The brains interpretation of sensory images. Occurs after the process of sensation. The process of understanding and interpreting sensory information, enabling us to recognize meaningful objects and events.

Extrasensory Perception (ESP)

The controversial claim that perception can occur apart from sensory input; includes telepathy (mind-to-mind communication), clairvoyance (perceiving remote events, such as a house on fire in another state), and precognition (perceiving future events, such as an unexpected death in the next month). While perception is fed by sensation, cognition, and emotion, this claims that sensory input is not necessary.

Hue

The dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth

Wavelength

The distance from the peak of one light or sound wave to the next. Electromagnetic wavelengths vary from the short blips of gamma rays to the long pulses of radio transmission.

Selective Attention

The focusing of conscious awareness on a particular stimulus

Audition (Hearing)

The hearing process occurs in several steps: Sound waves, vibrations in the air, travel through the air, and are then collected by our ears. Sound waves have amplitude and frequency. Amplitude is the height of the wave and determines the loudness of the sound, which is measured in decibels. Frequency, which is measured in megahertz, refers to the length of the waves and determines pitch. Vibrations enter the ear and vibrate the eardrum, which connects with three bones in the middle ear: the hammer (or malleus), the anvil (or incus), and the stirrup (or stapes), The vibration is transferred to the oval window, a membrane very similar to the eardrum. The oval window membrane is attached to the cochlea, where the process of transduction occurs and neural messages are sent to the auditory cortex in the temporal lobe.

Absolute Threshold

The minimal amount of stimulus we can detect 50% of the time. For example, the absolute threshold for vision is the smallest amount of light we can detect, which is estimated to be a single candle flame about 30 miles (48 km) away on a perfectly dark night.

Frequency

The number of complete wavelengths that pass a point in a given time (for example, per second) In hearing, measured in Hertz (Hz) Determine the pitch of the tone heard

Figure-Ground

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

Grouping

The perceptual tendency to organize stimuli into coherent groups

Weber's Law

The principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount). Named after psychophysicist Ernst Weber. Describes the difference thresholds for different senses. The change needed is proportional to the original intensity of the stimulus. The more intense the stimulus is, the more it will need to change before we notice a difference. For example, if you are playing very quiet music, you don't have to raise the volume much before someone notices. If the music is very loud, however, you have to raise the volume a lot before anyone will notice.

Visual Accommodation

The process by which the eye adjusts (by the lens changing shape) and is able to focus, producing a sharp image at various, changing distances from the object seen.

Cochlea

The process of transduction (where sound waves are changed into neural impulses) occurs here. Shaped like a snail's shell and filled with fluid. As sound waves move the fluid, hair cells move. Neurons are activated by the movement of the hair cells. Neural messages are sent to the auditory cortex in the temporal lobe.

Parallel Processing

The processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving.

Chemical Senses

The senses of taste and smell. These senses work by gathering chemicals.

Energy Senses

The senses of vision, hearing, and touch. These senses gather energy in the form of light, sound waves, and pressure, respectively.

Parapsychology

The study of paranormal phenomena, including ESP and psychokinesis/telekinesis (the supposed ability to move objects by mental effort alone)

Psychophysics

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

Transduction

The translation of incoming stimuli into neural signals (impulses) that our brain can interpret.. Neural impulses from the senses travel first to the thalamus and then onto different cortices of the brain. The sense of smell is one exception to this rule.

Place Theory (Pitch)

Theory that explain how we hear different pitches or tones. Place Theory explains that the hair cells in the cochlea respond to different frequencies of sound based on where they are located in the cochlea.

Frequency Theory (Pitch)

Theory that explain how we hear different pitches or tones. The rate of nerve impulses traveling up the auditory nerves matches the frequency of the tone, thus enabling us to sense its pitch. Also called temporal theory. Place Theory accurately describes how hair cells sense the upper range of pitches but not the lower tones. Lower tones are sensed by the rate at which the cells fire. We sense pitch because the hair cells fire at different rates (frequencies) in the cochlea.

Touch

This sense is activated when our skin is indented, pierced, or experiences a change in temperature. Some nerve endings in the skin respond to pressure; others respond to temperature. The brain interprets the amount of indentation (or temperature change) as the intensity of the touch, from a light touch to a hard blow. We sense placement of the touch by the place on our body where the nerve endings fire. Nerve endings are more concentrated in different parts of our body. If we want to feel something, we usually use our fingertip, an area of high nerve concentration, rather than the back of our elbow, area of low nerve concentration. - Pain is a useful response because it warns us of potential dangers.

Vestibular Sense

This sense tells us about how our body is oriented in space. Three semicircular canals in the inner ear give the brain feedback about body orientation. When the position of your head changes, the fluid moves in the canals, causing sensors in the canals to move. The movement of these hair cells activate neurons, and their impulses go to the brain. For example, this sense helps us figure out which way is up or down when doing a flip.

Sound Waves

Vibrations in the air. They travel through the air and are collected by our ears. Sound waves have amplitude and frequency. Amplitude is the height of the wave and determines the loudness of the sound, which is measured in decibels. Frequency, which is measured in megahertz, refers to the length of the waves and determines pitch.

Brightness/Color Constancy

We perceive objects as being a constant color even as the light reflecting off the object changes. For example, we will perceive a brick wall as red even though the daylight fades and the actual color reflected from the wall turns gray.

Synesthesia

When one kind of sensory stimulus evokes the subjective experience of another. Neurons for different types of cognition or sensation may be linked together in the brain. For example, hearing music may activate color-sensitive cortex regions and trigger a sensation of color. People who experience such sensory shift are called synesthetes.

Top-Down Processing

When we use this, we perceive the filling in gaps in what we sense. Information processing guided by higher level mental processes, as when we construct perceptions drawing on our experience and expectations. Occurs when you use your background knowledge to fill in gaps in what you perceive. Our experience creates schemata, mental representations of how we expect the world to be. Our schemata influence how we perceive the world. Schemata can create a perceptual set, which is a predisposition to perceiving something in a certain way.

Sensory Interaction

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

Opponent-Process Theory

- A theory of color vision. - States that the sensory receptors arranged in the retina come in pairs: red/green pairs, yellow/blue pairs, and black/white pairs. - If one sensor is stimulated, its pair is inhibited from firing. This theory explains color afterimages. - If you stare at the color red for a while, you fatigue the sensors for red. Then when you switch your gaze and look at the blank page, the opponent part of the pair for red will fire, and you will see a green afterimage. - The Opponent-Process Theory explains afterimages and colorblindness. - Most researchers agree that color vision is explained by a combination of the Trichromatic and Opponent-Process Theories.

Vision

- Dominant sense in human beings. Sighted people use vision to gather information about their environment more than any other sense. - The process of vision involves several steps: 1. Light is reflected off objects. 2. Reflected light coming from the object enters the eye through the cornea and pupil, is focused buy the lens, and is projected onto the retina where specialized neurons are activated by the different wavelengths of light. 3. Transduction occurs when light activates the special neurons in the retina and sends impulses along the optic nerve to the occipital lobe of the brain. 4. Impulses from the left side of each retina (right vision field) go to the left hemisphere of the brain, and those from the right side of each retina (left vision field) go to the right side of the brain. 5. Visual cortex receives the impulses from the retina, which activate feature detectors for vertical lines, curves, motion, among others. What we perceive visually is a combination of these features.

Gate-Control Theory

Explains how we experience pain. The theory that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. The "gate" is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers or by information coming from the brain. Some pain messages have a higher priority than others. When a high-priority message is sent, the gate swings open for it and shut for low-priority messages, which will not be felt. Of course, this gate is not a physical gate swinging in the nerve; it is just a convenient way to understand how pain messages are sent. For example, when you scratch an itch, the gate swings open for your high-intensity scratching and shuts for the low-intensity itching; this stops the itching for a short period of time. Endorphins, or pain-killing chemicals in the body, also swing the gate shut. Natural endorphins in the brain, which are chemically similar to opiates like morphine, control pain.

Inattentional Blindness/Change Blindness

Failing to see visible objects when our attention is directed elsewhere Failing to notice changes in the environment is more specifically known as change blindness, a type of inattentional blindness.

Kinesthetic Sense (kinesthesia)

Gives us feedback about the position and orientation of specific body parts. Receptors in our muscles and joints send information to our brain about our limbs. This information, combined with visual feedback, lets us keep track of our body.

Cocktail-Party Phenomenon

If you are talking with a friend and someone across the room says your name, or something else of particular interest to you, your attention will probably involuntarily switch across the room. An example of selective attention.

Embodied Cognition

In psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments. For example, physical warmth may promote social warmth, while social exclusion can literally feel cold.

Color Blindness

Individuals with dichromatic color blindness cannot see either red/green shades or blue/yellow shades. Those who have monochromatic color blindness see only shades of gray.

Signal Detection Theory

Investigates the effects of the distractions and inferences we perceive while experiencing the world. Predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motvation, and alertness. Theory that takes into account how motivated we are to detect certain stimuli and what we expect to perceive. These factors together are called response criteria. By using factors like response criteria, Signal Detection Theory tries to explain and predict the different perceptual mistakes we make (such as not seeing a stop sign, or thinking that you see a friend in the distance when you are actually seeing a stranger).

Occipital Lobe

Location of visual cortex. Part of the brain that processes vision sensations. -Receives impulses via the optic nerve. The optic nerve is divided into two parts. Impulses from the left side of each retina (right visual field) go to the left hemisphere of the brain, and those from the right side of each retina (left visual field) go to the right hemisphere of the brain.

Smell (or Olfaction)

Molecules of substances rise into the air and are drawn into our nose. The molecules settle in a mucous membrane at the top of each nostril and are absorbed by receptor cells located there. As many as 100 different types of smell receptors may exist. These receptor cells are linked to the olfactory bulb, which gathers the messages from the olfactory receptor cells and sends this information to the brain. Nerve fibers from the olfactory bulb connect to the brain at the amygdala and then to the hippocampus, which make up the limbic system, which is responsible for emotional impulses and memory. This direct connection to the limbic system may explain why smell is such a power trigger for memories.

Taste (or Gustation)

Nerves involved in the chemical senses (taste and smell) respond to chemicals rather than to energy. Taste buds on the tongue absorb chemicals from the food we eat. Taste buds are located on papillae, the bumps you can see on your tongue. Taste buds are located all over the tongue and on some parts of the inside of the cheeks and roof of the mouth. Humans taste five different types of tastes: sweet, salty, sour, bitter, and umami. People differ in their ability to taste food. The more densely packed the taste buds, the more chemicals are absorbed, and the more intensely the food is tasted. The flavor of food is actually a combination of taste and smell.

Size Constancy

Objects closer to our eyes will produce bigger images on our retinas, but we take distance into account in our estimations of size. We keep a constant size in mind for an object (if we are familiar with the typical size of the object) and know that it does not grow or shrink in size as it moves closer or farther away.