Chapter 4 - Sensation and Perception Flashcards
What is a sensation?
the reception of stimulation from the environment
Detection of physical energy by sense organs, which then send information to the brain
what is perception?
the interpretation of sensory information; often an automatic process
what are some examples of automatic processes from perception?
- pattern recognition; categorization
- link sensory information to existing knowledge
2 examples of sensation
auditory
visual
what are examples of automatic perception?
to recognize faces
to recognize whether you are sitting or walking
happens effortlessly
what is top-down knowledge?
pre-existing beliefs or assumptions guide one’s interpretation and understanding of new information.
what is bottom-up processing?
an approach to a perception that starts with incoming sensory information and uses it to build a perception of the world. It involves processing data step-by-step, from individual sensory details to a more complex understanding of the whole.
Bottom-up processing is like building with legos. You start with small pieces and put them together to make something bigger and more complex. In the same way, our brains start with tiny bits of information that come in through our senses, like what we see, hear, or touch, and use them to create a bigger picture of what’s happening around us.
how do sensation and perception work?
Raw data: basic information that is received through our senses, such as what we see, hear, smell, taste, or feel
Attention: the process by which we selectively focus our awareness on certain aspects of our sensory input while ignoring others.
Expectations and previous knowledge: the role that our prior experiences and expectations play in shaping our perception of sensory information. Comes from top down knowledge
how is sensory data translated?
into information used by our nervous system
what is transduction?
the process of converting an external stimulus into electrical activity within neurons
what are sensory receptors? (transduction)
special cells for converting external stimuli into neural activity
when is sensory adaptation greatest? (transduction)
activation is greatest when a stimulus is first detected
what is psychophysics?
“PSSPC”
the study of how we perceive sensory stimuli based on their physical characteristics
What is Absolute Threshold (psychophysics)
the lowest level of stimulus needed to be detected by the nervous system 50% of the time
What is an example of an absolute threshold?
If a person can hear a sound of 10 decibels, but not a sound of 5 decibels, then the absolute threshold of that person’s hearing is 10 decibels.
The final threshold varies from person to person and from the sensory system to the sensory system.
What is just a noticeable difference (JND)? (psychophysics)
the smallest change in the intensity of a stimulus that we can detect
what is Weber’s Law? (psychophysics)
the constant proportional relationship between the JND and the original stimulus intensity
What does JND stand for
just noticeable difference
What does light equal?
Light = electromagnetic radiation
What range do we only perceive of wavelengths?
narrow range
how do we measure wavelengths?
nanometers
what appears as different colors?
wavelengths
what is the retina?
innermost layer of the eye, where incoming light is converted into nerve impulses; contains photoreceptor cells
what is the vitreous humor (eye)
the jelly-like liquid that nourishes and gives shape to the eye
what is the iris? (eye)
colored area containing muscles that control the pupil
what is aqueous humor?
clear liquid that nourishes the eye
what is the pupil?
opening in the center of the iris that changes size depending on the amount of light in the environment
what is the cornea?
the curved transparent dome that bends incoming light waves so the image can be focused on the retina
what is the lens? (eye)
a transparent disc that changes shape to bring objects into focus
what is the fovea? (eye)
central area of retina where light rays are most sharply focused; greatest density of cones
what is the blind spot? (eye)
(optic disc) where the optic nerve leaves the eye; there are no photoreceptor cells here
what is the optic nerve? (eye)
transmits visual information from the retina to the brain
what is the eye muscle?
one if six surrounding muscles that rotate the eye in all directions
The retina:
at the back of the eye – responsible for visual transduction
where does the process of transduction occur?
in photoreceptors (rods and cones)
what is transduction?
refers to the conversion of physical stimuli (such as light, sound, or pressure) into electrical signals that can be processed by the nervous system.
what are photoreceptors?
specialized cells found in the retina of the eye that is responsible for detecting light and transmitting visual information to the brain.
There are two main types of photoreceptors: rods and cones.
what are rods and cones?
two types of photoreceptor cells found in the retina of the eye that is responsible for detecting light and transmitting visual information to the brain.
what are rods? (photoreceptors)
vision at low levels of light
Dark adaptation: gradual improvement in sensitivity of rods after a shift to near darkness
what is dark adaptation?
gradual improvement in sensitivity of rods after a shit to near darkness
refers to rods
what are cones?
vision at higher levels of light
Sensitive to light and fine detail
what is sensitive to light and fine detail? (photoreceptors)
cones
What are the Ganglion Cells?
cells that receive neural impulses and transmit information out of the eye
Axons from optic nerve
what is the optic nerve?
a bundle of nerve fibers that carries visual information from the retina of the eye to the brain.
what do rods and cones contain?
photopigments
different sensitivity thresholds
when does the transduction of light into neural energy occur?
through absorption of photons
7 photons of light can produce a visual response
how many photons o light can produce a visual response?
7
what is a photon?
a fundamental particle of light and other forms of electromagnetic radiation. It is a type of elementary particle, which means that it has no mass and travels at the speed of light.
what 2 things occur with pigment?
it isomerizes (changes form
sensitivity to light is reduced
what is the trichromatic theory?
Base our color vision on three primary colors
Red, green, and blue
how many different types of cones are there?
three
what are trichromats?
organisms that possess three types of color-sensitive photoreceptor cells, also known as cones, in their eyes.
what is colour blindness?
Inability to see some or all of the colours
Often due to the absence or reduced number of one type of cones
what are monochromats?
one type of cone, no colour vision
what are dichromats?
often have difficulty with shades of red and green
what is opponent process theory?
We perceive color using opponent cells
Red-green
Blue-yellow
Black-white
where is there evidence for opponent processes for visual perception?
in the ganglion cells, thalamus, and visual cortex
what can we not see?
two of the opposing colors in the same space
No reddish-green or yellowish-blue
when does the complimentary color appear?
after-images appear according to a pattern
what evidence is there to support both theories?
three types of cones
opponent processes in eye and brain
how do the theories work as complimentary with each other?
cone system produces opponent processes later in the visual process
what have specialized neurons?
visual areas
what are two important points about visual areas of specialized neurons?
different receptive fields and activated by different triggers
Receptive field: an area on the retina to which a neuron will respond
what is a receptive field?
an area on the retina to which a neuron will respond
what are center-surround cells?
“Dot Detectors”: neural cells in the visual system that respond selectively to specific arrangements of visual inputs, such as patterns of dots or oriented edges. These cells are important for the processing of visual information in the brain and are found in the primary visual cortex, which is the first stage of cortical processing in the visual pathway.
how do center-surround cells fire?
when light is presented to a small circular are in a specific location of retina
when are center-surround cells produced?
by the organization of receptors and ganglion cells
what are feature detection cells?
Detect lines and edges
Vary in complexity
what are simple cells?
detect lines and edges in very specific locations and orientations
what are complex cells?
Detect lines and edges in less restricted locations
Bottom-up/Data-Driven Processing
Analysis and integration of basic features into a perceptual unit
Feature combination which create an object
explain bottom-up processing
Bottom-up processing refers to the way our brain processes information by focusing on individual parts and building up to a whole picture, like putting together a puzzle. It’s a fundamental way that our brain makes sense of sensory information from the world around us.
hierarchical organization
form perceptual units through a process of increasingly complex connections between simple units
where does hierarchical organization take place?
in different areas of the visual cortex and connected areas (eg. in temporal and parietal lobes)
what is parallel processing?
A system in which many different steps happen simultaneously
E.g., perception of many different features (e.g., shape, orientation, color)
advantages of parallel processing?
Fast processing
Allows for top-down processing
- Each type of processing can be influenced by
the others
what is top - down processing?
A.K.A. Conceptually-driven processing
When context and higher-level knowledge influence lower-level processes
what is not a perfect representation of the world and why?
perception
it is influenced by many factors, including our prior knowledge, expectations, attention, and the context in which we experience things.
what does form perception refer to?
perception of defined visual elements in the environment
- Objects, shapes, visual scenes - Recognizable wholes
what do we do without conscious effort?
readily process information
do not have to mentally “assemble the features”
what did Gestalt Theory focus on?
the whole rather than the individual parts
what is the principle of simplicity?
when we have sensory input our perceptual system usually tries to create a percept that is:
- Simple
- orderly
- stable
principle of simplicity
also known as Occam’s razor or the law of parsimony, is a guiding principle that states that when there are multiple explanations for a phenomenon, the simplest explanation is usually the best. In other words, when we are trying to understand something, we should look for the explanation that requires the fewest assumptions or variables.
This principle is often applied in scientific research, where researchers strive to develop theories that are simple, elegant, and parsimonious. The goal is to create theories that explain a wide range of phenomena with a minimal number of assumptions or variables.
law of proximity
objects that are physically close to each other tend to be perceives as unified wholes or groups
what is the law of similarity?
similar visual element form a whole
- similar things are grouped together
(shape, colour, etc)
what is the law of closure?
objects are perceived as whole, even if they are not complete
what is the law of good continuation?
Also known as law of continuity
we tend to perceive objects as forming smooth continuous patterns
what is the law of symmetry?
objects that are around a center point format group or whole
what is the law of figure-ground segregation?
tendency to structure the visual field into two parts: a figure and a background
bistable percepts: stimuli can be perceived in one of two different ways
What do Gestalt principles give us insight into?
some of the ways we perceive form
what can be considered a problem-solving process?
pattern and object recognition
how does brain judge motion?
by rapidly comparing visual frames
what is visual information from one frame compares to?
what is processed next
what is the phi phenomenon?
perception of motion when stationary objects are flashed in quick succession
what is the perception of movement based on?
partial information
what is an analogy for visual perception?
much like a movie. it’s like a visual frame.
perceptual vision takes in information in rapid short bursts
what is depth perception?
the ability to see spatial relations in three dimensions and judge distance
what are monocular depth cues?
Pictorial Cues:
- Relative Size - Texture Gradient - Interposition - Linear Perspective - Height - Light and Shadow
What is depth through motion?
motion parallax
(The car goes by slowly if far away. The car goes by fast if closer)
What is depth through motion?
motion parallax
a visual depth cue that helps us perceive the relative distances of objects in our environment by using motion. This cue is based on the idea that when we move, objects at different distances appear to move at different rates in our visual field.
(The car goes by slowly if far away. The car goes by fast if closer)
what are binocular depth cues?
The brain uses the differences between the two views to create a sense of depth and three-dimensionality.
Binocular disparity
binocular convergence
binocular disparity
each eye transmits slightly different information to the brain
(eye will turn inward)
what is binocular convergence?
eyes turn inward to differing degrees when we focus on near objects
redundancy in-depth perception…
Many visual cues, both monocular and binocular provide similar information
perceptual constancy
we perceive the properties of objects to be constant even though the stimuli around us change when the viewing circumstances change
what does perceptual constancy apply to?
size, shape, colour
example of perceptual constancy
if we see a red apple in a dimly lit room, and then we see the same apple in bright sunlight, we still recognize it as the same object, even though the lighting conditions and the sensory information we receive are different.
what are unconscious inferences?
we combine information from the stimulus with other cues from the environment to drive perception
the process by which our brain makes assumptions and fills in missing information in our perception of the world without us consciously realizing it. It is an automatic and often unconscious process that helps us make sense of the sensory information we receive.
example of unconscious inference:
when we see a partially hidden object, our brain automatically fills in the missing parts based on our past experience and expectations. Similarly, when we see a blurry image, our brain makes assumptions about what the image might be based on our past experience and context.
what is size constancy?
our ability to perceive objects as the same size no matter how far away they are from us
- Retinal image varies in size, perception remains constant
what do we perceive size on the basis of?
apparent distance
what perception is a nonconscious process?
visual perception
what basis do we perceive size on?
apparent distance.
A non-conscious process
what is shape constancy?
Our ability to perceive shapes as constant even as objects move or we move in relation to them
The retinal image of the shape actually changes
what is Colour Constancy?
We perceive colours as (relatively) constant across lighting conditions, even though the actual image differs
use cues based on context/background
Colour Vision theories:
Trichromatic and Opponent Process
theory are two different explanations of how humans perceive color.
Shape and contour explanation:
Center-surround cells and feature detectors
two types of neurons in the visual system that are involved in processing shape and contour information.
basic perceptual principles:
emphasizes the importance of perceptual organization and the ways in which people naturally organize their perceptions of the world into meaningful patterns or wholes, rather than just a collection of individual parts. The term “gestalt” comes from the German word for “shape” or “form.”
Gestalt laws:
Law of proximity: Elements that are close together in space are perceived as a group.
Law of similarity: Elements that are similar in shape, size, color, or texture are perceived as a group.
Law of closure: People tend to perceive incomplete figures or shapes as complete by filling in the missing information.
Law of good continuation: People tend to perceive continuous lines and patterns rather than discontinuous ones.
Law of figure-ground: People tend to perceive objects as either being in the foreground (the figure) or the background (the ground).
Motion, depth, constancy:
Motion, depth, and constancy are three important principles of perception that allow us to make sense of the world around us.
Motion, depth, constancy:
Motion, depth, and constancy are three important principles of perception that allow us to make sense of the world around us.
Motion, depth, constancy principles:
Motion perception: ability to perceive the movement of objects in the environment. This ability is based on the processing of visual cues such as changes in the size or shape of objects, changes in position over time, and changes in brightness or color. important for many everyday tasks, such as tracking moving objects, avoiding collisions, and navigating through the environment.
Depth perception: Depth perception refers to our ability to perceive the spatial relationships between objects in the environment. This ability is based on visual cues such as overlap, linear perspective, and shading. Depth perception is important for many everyday tasks, such as judging distances, reaching for objects, and navigating through the environment.
Constancy: Constancy refers to our ability to perceive objects as having stable properties, even when the sensory information we receive changes. For example, we perceive a door as having a constant size and shape even when it appears larger or smaller based on our distance from it. Constancy is important for allowing us to recognize objects in different contexts and under different viewing conditions.
Putting it all together:
Bottom-up + Top-down processing
Parallel Processing
Bottom-up VS. Top-down processing
Bottom-up:
it is driven by the physical features of the sensory input, such as color, shape, or texture. This approach is sometimes called data-driven processing because it relies on the incoming data to create meaning.
Top-down:
the way sensory information is processed in a way that is influenced by our prior knowledge, expectations, and beliefs. This approach is sometimes called conceptually-driven processing because it involves using higher-level cognitive processes to interpret incoming sensory information.
parallel processing?
multiple tasks or processes are performed simultaneously by different parts of the brain. In other words, instead of completing one task at a time, the brain is able to divide tasks into smaller sub-tasks and process them in parallel.
what visual perception can fail?
Object or pattern recognition
what visual perception can fail?
Object or pattern recognition
what is agnosia?
A failure or deficit in recognizing objects
The basic visual sensory system works
Prosopagnosia
deficit in recognizing faces
Prosopagnosia
deficit in recognizing faces
apperceptive agnosia
deficit in recognizing patterns
associative agnosia
deficit in associating meaning and a pattern
what is sound?
The mechanical energy in the form of vibrations traveling through a medium (e.g., gas, liquid, solid) transmitted in waves
Hear best when it travels through the air
Two physical properties of the auditory system?
Frequency: The number of cycles a wave completes in a given time
Measured in Hertz: cycles per second
Pitch: 20 – 20,000 Hz
Amplitude: height of the sound wave
Measured in decibels (dB)
Loudness: 0 – 160 dB
parts of the outer ear:
Pinna: channels sound
Auditory Canal: channels sound to the eardrum
Eardrum: thin membrane that vibrates according to the frequency
what does the middle ear contain?
Ossicles - a group of three small bones located in the middle ear.
They are known as the malleus, incus, and stapes, and are often referred to as the hammer, anvil, and stirrup, respectively. The ossicles connect the eardrum to the inner ear and are essential for hearing.
middle ear: contains ossicles
Hammer, anvil, stirrup: vibrate at the frequency of the sound; transfer the vibrations to the inner ear
Inner Ear:
oval window: receives amplified sound from ossicles, which cause vibrations in the fluid of the cochlea
organ of corti: contains hair cells that are stimulated by different vibrations and perform the process of transduction
what is place theory?
pitch perception
Different frequencies stimulate different locations on the basilar membrane
what is a basilar membrane?
narrow and stiff at the base; wide and flexible at the apex
what selectively vibrates basilar membrane?
waves
higher pitch sounds do not travel as fas as lower pitch sounds
what does not travel as far as lower-pitch sounds?
higher pitch sounds
frequency theory:
tones with different frequencies cause neurons to fire at different rates
explains low-frequency range for pitch perception; maximum 100-500 Hz
volley theory:
sets of neurons fire just out of sync with each other to code for frequency above the rate at which neurons can fire
frequency between 500-5000 Hz
how does the brain make comparisons?
sounds reach ears at (slightly) different times and intensities
Interaural level (intensity) difference:
sounds arrive at each ear at different times due to different spatial locations
The brain calculates subtle differences in the arrival of sound at each ear
Most effective for low frequencies
olfaction
sense of smell
smell guides (or biases) taste
how is smell a chemical sense?
chemicals in substance bind to receptors
chemicals must be volatile (airborne)
what are humans capable of detecting?
a large variety of smells
what can be underestimated?
human olfaction (sense of smells)
Volatile chemical
substances are picked up by olfactory receptor cells
each olfactory cell detects one type of compound
what are odors based on?
complex coding
where is the “smell” message sent to?
olfactory bulbs
Relayed to the limbic system and other areas
No Thalamus
Odors can evoke memories
what is gustation?
chemical sense
the ability to detect and perceive the chemical composition of substances in the mouth, primarily through the action of taste receptors on the tongue.
where is air force as we chew?
into the nasal cavity
what is much of what we chew based in?
olfaction (sense of smells)
what is critical for sampling food?
Taste (along with smell)
five major tastes
Sweet, salty, sour, bitter, umami
Some evidence for “fatty” and “starchy”
Taste maps are a myth
what are a myth?
taste maps
diagrams or illustrations that depict the distribution of taste receptors on the tongue and the corresponding areas of taste perception. The idea of taste maps originated from a misinterpretation of a study in the early 20th century, which suggested that different regions of the tongue were more sensitive to specific tastes. However, subsequent research has shown that all tastes can be detected in all regions of the tongue, although certain regions may be more sensitive to certain tastes. Taste maps are now considered a popular myth and are not supported by modern scientific evidence.
what do taste buds detect?
taste
soluble chemical substance
situated in gaps between papillae
what comes in different routes, but are combined in the brain?
sensory information for smell and taste
what affects preferences and what disgusts us?
culture
somatosensory
sense of touch, pressure, temperature, and injury
what is very specific or generalized?
stimulation
how do we sense somatosensory stimuli?
Free Nerve Endings
- Can be polymodal
- Are often nociceptors
Other specialized nerve endings
- Slow and fast-adapting
- Many types: can be very specialized
how does the perception of touch and pain travel?
via somatic nerves to spinal cord
what may trigger spinal reflexes?
somatic information
withdrawal reflex
pull away prior to conscious decision
where is the information sent to?
somatosensory cortex and associational areas (to be combines with other information)
Proprioception:
Our sense of body position
Proprioceptors sense muscle stretch and force
Vestibular Sense:
Our sense of equilibrium or balance
Semicircular canals are filled with fluid; connected to utricle and saccule
Information is sent to parts of brainstem that control eye muscles
Bringing many senses together
Perception does not perfectly match reality – it is constructed by the brain
parallel processing
the brain processes many types o information simultaneously to give you a perception of the world
