Unit 3: Sensation and Perception

Gustav Fechner

A German psychologist who founded psychophysics. This field essentially studies the relationships between physical characteristics of stimuli, and psychological experiences. For example: light - brightness, sound - volume, pressure - weight, sugar - sweet.

Convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object. Real World Example: Our eyes will move inward in order to see something that is closer, and outward in order to see things that are further away, showing how we can perceive depth with two eyes.

Gestalt Psychology

A field of psychology that emphasizes that we often perceive the whole rather than the sum of the parts. Real World Example: The Necker cube is an illusion that shows an example of Gestalt beliefs. It is essentially a bunch of circles with lines through them that are not directly connected, but our mind connects them to form a cube that is not actually there.

Perceptual Set

A mental predisposition to perceive one thing and not another. Real World Example: People may look at a picture and believe that something the shape of a cylinder is a tree, or a column depending on what they expect to be in images. If they are constantly around nature, they will use their experiences and create expectations that the cylinder is a tree.

Retina

A multilayered, light sensitive tissue on the inner surface of the eye that converts light particles into neural messages. Real World Example: The retina receives focused light from the lens and uses its receptors to change the light into neural messages, which can be sent to the occipital lobe to be interpreted.

David Hubel

A neuroscientist who won a Nobel Prize for his research in feature detection. He helped to show how different feature detectors in the brain can respond to specific features in images, such as certain angles, shapes, etc.

Torsten Wiesel

A neuroscientist, who along with David Hubel, won a Nobel Peace Prize for research in feature detection. They both discovered these nerve cells, that respond specifically to certain features. They found that these detectors received information from individual ganglion cells and that they would pass specific information to other cortical areas.

Eleanor Gibson

A psychologist who performed the "visual cliff" experiment. This experiment used babies to test whether they could use depth perception to avoid a "fall." Results of these experiments proved that depth perception is innate, as babies would not crawl across the "cliff."

Ernest Weber

A scientist who came up with Weber's Law, the idea that for humans to notice a difference between two stimuli, they must differ by a constant percentage. (Light-8, Weight-2, and Tone-.3). They must differ in percentage.

Lens

A transparent structure behind the pupil that focuses light rays into an image on the retina. Real World Example: The lens receives light that is let into the eye by the pupil and iris and focuses it onto the retina in the back of the eye. If the eye is deformed however, the lens will not properly project the light, which causes near or farsightedness.

Proximity

A type of grouping that shows how our minds group things that are closer to each other. Real World Example: Given a set of 6 lines, with pairs of lines closer together, and separated with longer distance between each pair, our minds will see the lines as 3 pairs rather than 6 individual lines. This is because the lines are close together.

Bottom-up Processing

An analysis that begins with the sensory receptors and works up to the brain's integration of sensory information. Real World Example: When you touch and feel an object, this is bottom-up processing. The sensory receptors in your hand send messages up to the brain, which interprets the feeling.

Phi-Phenomenon

An illusion of movement created when two or more adjacent lights blink on and off in quick succession. Real World Example: Neon signs in store windows may have lights that blink in succession around the word "open." This provides the illusion that there is a light going in circles around the word.

Feature Detectors

Brain nerve cells that respond to specific features of stimuli, such as shape, angle, or movement. Real World Example: Feature detectors receive information from individual ganglion cells and respond to specific angles, shapes, etc. They then pass them on to supercell clusters, which respond to more complex patterns.

Sensory Adaption

Decreased sensitivity to a constant stimulus due to an organism adapting to its conditions. Real World Example: People won't feel their shoes after wearing them for a while. This is because constant stimulation to the sensory neurons in the feet causes them to fire slower, until it simply adapts to ignore the sensation.

Color Blindness

Deficiency in the ability to distinguish among colors. Real World Example: This is caused because of a lack of certain color receptor cones. Because cones are responsible for our ability to interpret colors, a lack in a certain type will hinder the ability to perceive that color normally. Red-green colorblindness is an example of this, where the person cannot see much difference in red and green.

Sensorineural/Nerve Deafness/ Hearing Loss

Hearing loss caused by damage to the cochlea's receptor cells or the auditory nerve. Real World Example: Can be caused by heredity, aging, and blasting music. It can be treated by cochlear implants, which actually stimulate auditory nerves.

Conduction Deafness/Hearing Loss

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea. Real World Example: This can be treated with hearing aids that help to replace the ear drum and inner ear bones. Punctured ear drums are an example of this type of hearing loss.

After-Images

Images that occur when a visual sensation persists for a brief time even after the original stimulus is removed. Real World Example: When staring at an image, such as a flag, on a white background for a while, someone can look away onto an empty white background and still see the flag with opponent colors showing.

Top-Down Processing

Information processing guided by higher-level mental processes, as when we construct perceptions. Real World Example: When our brain perceives optical illusions, this is a top-down process. We use the sensory information to interpret a picture.

Sensory Habituation

Perception of sensation can be affected by how much we focus on them. Real World Example: Athletes who are in the middle of a game will not feel a twisted ankle, or a sore muscle until they focus on it. If they are distracted with the sport, then they won't notice the pain.

Cones

Retinal receptor cells near the center of the retina and that function in well-lit areas, and detect fine detail and give rise to color sensations. Real World Example: Cones are located in clusters around the fovea of the retina. They allow us to see the color and fine details of the classroom, each other, and everything else in the world. When people have red-green cone deficiency, it can cause color blindness.

Rods

Retinal receptors that detect black, white, and gray, helping with night and peripheral vision. Real World Example: There are more rods in the eye than cones. They can allow us to see a car in our peripheral visions at night, before we can notice details using our cones. This is due to the rods being more sensitive in dim lights.

Kinesthetic Sense

Sense of the location of body parts in relation to the ground and each other. Real World Example: Without kinesthetic sense, it would be very difficult to walk or have any coordination at all. However, some people with a condition that prevents kinesthetic sense, are able to walk and move by looking at their feet or limbs.

Sound Waves

Sound travels in waves of compression and rarefaction, which can affect how we hear sounds. Real World Example: When someone speaks, sound waves travel from them to your ear, where they are converted into neural messages and sent to the temporal lobes for interpretation.

Cocktail Party effect/phenomenon

The ability to attend to only one voice among many. Real World Example: During a party, if a friend calls your name, you can tune the other surrounding people out in order to converse only with the individual.

Selective Attention

The ability to focus on a single stimulus while having other stimuli in the environment. Real World Example: When given a crowd of people, we can focus on one person who we seem to recognize. We pay attention to the single person rather than the entire crowd.

Frequency

The distance between the peaks of waves. Real World Example: High pitched sounds and bluish colors have higher frequencies (closer waves), while low pitched sounds and reddish colors have lower frequencies.

Amplitude

The height of a sound or light wave. Real World Example: Bright neon colors that we see in highlighters have high amplitude light waves that go to our eyes. Loud sounds, such as the sound of music at concerts, also have high amplitude waves.

Trichromatic Theory

The idea that the retina contains only three different color receptors (red, green, and blue) that are used to perceive any color. Real World Example: We are able to see every color possible for humans because of the three different types of color receptors. This is why, when someone has a deficiency of one or more types of these receptors, they are unable to perceive colors using the receptors.

Weber's Law

The just noticeable difference of a stimulus is at a constant percentage despite variations in intensity. Real World Example: We will notice the difference in temperature of a room when it changes by a set percentage.

Closure

The mind's tendency to complete figures that are incomplete. Real World Example: We tend to fill in gaps to create a whole figure. Given three shapes that have an empty spot cut out of them, which happen to align into a triangle if put together, our mind will ignore the empty gaps and automatically see the triangle.

Difference Threshold

The minimum difference between two stimuli required for detection Real World Example: If the temperature of water is gradually increased, so that it does not pass the difference threshold, we will not notice a change.

Threshold

The minimum level of stimulation required to trigger a neural impulse Real World Example: To be noticed, different sensations of touch must have a certain amount of pressure in order to trigger a neural response that is noticed by the brain.

Absolute Threshold

The minimum stimulation needed to detect a particular stimulus 50 percent of the time. Real World Example: When someone is unable to discriminate between different similar animals from a distance, at least half of the time, then they have not reached their absolute threshold.

Optic Nerve

The nerve that carries neural impulses from the eye to the brain. Real World Example: The optic nerve is made up of the axons of ganglion cells. Any visual that a human sees is passed as neural messages from the eye to the brain. This can include just reading, or looking around a classroom. This is done by the optic nerve after transduction.

Pupil

The opening in the eye through which light passes through. Real World Example: The entrance in which light enters into the eye. It allows different parts of our eyes to use these light waves to form colors, shapes, depth, and anything needed to allow us to view images. It's shape is manipulated by the iris, and it will grow to take in more light, and shrink to take in less.

Blind Spot

The point at which the optic nerve leaves the eye and no receptor cells are located. Real World Example: When focusing on a central figure, or something like a dot, as we get closer, the objects to the sides of the central figure will eventually disappear. This is because they enter the blind spot of the eye, that our brain automatically tries to fill in.

Sensation

The process by which the sensory receptors and nervous system receive and represent stimuli. Real World Example: Sensation can be described as bottom-up processing, where information from the body's sensory receptors is sent to the brain. This can include touch, olfaction, seeing, hearing, and taste.

Transduction

The process of converting one type of energy into neural impulses our brains are able interpret. Real World Example: The retina's photoreceptors will be activated in response to light, causing bipolar cells to turn this into a neural message. The message travels through the optic nerve, and into the brains occipital lobe, where it can be interpreted.

Perception

The process of organizing and interpreting sensory information. Real World Example: Perception can be described as top-down processing, where the brain interprets the information that it gets from the senses. For example, our tendency to group close objects that we see together affects our perception of images.

Fovea

The retinal area of central focus. Real World Example: Here, the cones cluster around. This allows us to see with more focus and detail in the center of our vision, where cones are. We can see words on a page clearly in the center of our vision, while it is blurry further away from the center, or fovea.

Vestibular Sense

The sense of body movement and position, including the sense of balance. Real World Example: Humans can walk and maintain balance using the cerebellum. This allows our vestibular sense.

Chemical Senses

The senses which work by gathering chemicals; taste and smell Real World Example: These senses, which are picked up by our mouths and noses, are converted from chemicals to neural impulses that are sent to the brain. They can be taken in from different stimuli, specifically odor molecules, and chemicals in foods.

Gate-Control TheoryT

The spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain. Real World Example: The "gate" is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in larger fibers. Things like massage and distractions can cause large fiber activity, decreasing pain.

Size Constancy

The tendency to perceive an object as always being the same actual size, regardless of its distance. Real World Example: We know a car that is far away from us, despite seeming small, is big enough so that it can still hold multiple people inside.

Constancy

The tendency to perceive certain objects in the same way regardless of changing angle, distance, or lighting. Real World Example: Because of something like size constancy, if we infer that two objects are around the same size, we can determine that the smaller one in our view is actually farther away. This allows us to understand that things a far distance from us, are not actually as small as they appear.

Brightness Constancy

The tendency to perceive the apparent brightness of an object as the same even when the light conditions change. Real World Example: Whether a black paper is in the bright sun, and reflects a lot of light, or is in the shade, we can still see it as having the same apparent brightness compared to its surrounding conditions.

Shape Constancy

The tendency to perceive the shape of an object as being constant, even when its shape seemingly changes from different angles. Real World Example: A door, while shutting, will seem to change shape. Because of shape constancy, we can understand that the door is still a rectangle no matter the angle we see it from.

Similarity

The tendency to perceive things that look similar to each other as being part of the same group. Real World Example: Given 3 rows of shapes, with the first two rows being squares, and the last being circles, we will group alike shapes together and separate the squares from the circles.

Opponent-Processing Theory

The theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. Real World Example: When staring at an American flag with opponent colors (yellow, green, and black), you can look away and see an afterimage with the correct colors showing. This is because opponent colors can not work at the same time, and you have tired out your green color receptors.

Signal Detection Theory

The theory that we detect a stimulus among another stimuli based on our experiences, motivation, and fatigue level. Real World Example: We can focus on one object in an image because of our motivation to find said object.

Cornea

The transparent layer that covers the front of the eye, where light enters. Real World Example: The cornea is the first transparent area where light starts to enter the eye. It helps to bend light in order to focus it into the eye.

Monocular Depth Cues

The usage of one eye, which shows a 2D image, to perceive depth. Real World Example: Size constancy is a monocular depth cue that allows us to understand that something smaller, may mean that it is farther away.

Binocular Depth Cues

The use of both eyes to see depth in what eyes look at. Real World Example: The brain will compare the two different images taken by each eye and will compare them to judge and perceive depth in what we look at.

Energy Senses

Vision, hearing, and touch, which gather energy in light, sound waves, and pressure. Real World Example: Through transduction, these different types of energies taken in by our sensory receptors are converted into neural impulses that can be sent to the brain for interpretation. These senses cause the conversion of energy into neural impulses.

Subliminal Messaging/Threshold

When stimuli are below one's absolute threshold for awareness, but can have a subtle effect on someone. Real World Example: Priming someone to spell "sun" the way that it is spelled by subtly mentioning the outdoors is a form of subliminal messaging, or priming.

Retinal Disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance. Real World Example: The greater the difference between the two images, the closer the object is, allowing us to perceive depth.