Donald Deskey recognized the power of perception back in 1946 when he
Grabbed the attention of customers with an eye catching color on a tide box
Simple stimulation of a sense organ
The organization, identification and interpretation of a sensation in order to form a mental representation
What takes place when many sensors in the body convert physical signals from the environment into encoded neural signals sent to the central nervous system
What is the sensory input activating vision
Light reflected from surfaces (for example from a leaf) provides the eyes with information about the shape, color, and positions of objects
What is the sensory input activating audition (hearing)?
Vibrations cause changes in air pressure that move through space to the listener's ears
What is the sensory input activating touch?
Pressure of a surface against the skin signals its shape, texture and temperature
What is the sensory input activating taste and smell?
Molecules dispersed in the air or dissolved in saliva reveal the identity of substances that we may or may not want to eat
What role does the brain play in what we see and hear?
The brain interprets, organizes and perceives what we see and hear
What is the absolute threshold for vision?
A candle flame 30 miles away on a clear, dark night
What is the absolute threshold for hearing?
A clock's tick 20 feet away when all is quiet
What is the absolute threshold of touch?
A fly's wing falling on the cheek from 1 centimeter away
What is the absolute threshold of smell?
A single drop of perfume diffused through an area equivalent to the volume of six rooms
What is the absolute threshold for taste?
A teaspoon of sugar dissolved in two gallons of water
Methods that measure the strength of a stimulus and the observer's sensitivity to that stimulus
The minimum intensity needed to just barely detect a stimulus in 50% of the trials
Just noticeable difference (JND)
The minimal change in a stimulus that can just barely be detected
The just noticeable difference of a stimulus is a constant proportion despite variations in intensity
Why isn't it enough for a psychophysicist to measure only the strength of a stimulus?
Because we perceive things differently. What one person sees as a bright light another will see as a dim light
How accurate and complete are our perceptions of the world?
Our perceptions are not very accurate and complete because the brain has to filter out a lot of noise (other internal and external stimuli)
Signal detection theory
The response to a stimulus depends both on a person's sensitivity to the stimulus in the presence of noise and on a person's response criterion
Sensitivity to prolonged stimulation tends to decline over time as an organism adapts to current conditions
The ability to see fine detail
Sensation is the
Simple stimulation of a sense organ, whereas perception organizes, identifies and interprets sensation at the level of the brain
All of our senses depend on the process of transduction, which
Converts physical signals from the environment into neural signals carried by sensory neurons into the central nervous system
Sensory adoption occurs because
Sensitivity to lengthy stimulation tends to decline over time
Signal detection theory allows researchers to
Distinguish between an observer's perceptual sensitive to a stimulus and criteria for making decisions about the stimulus
In the 19th century researchers developed
Psychphysics, an approach to studying perception that measures the strength of a stimulus and an observer's sensitivity to that stimulus
Psychophysicists have developed procedures for measuring
An observer's absolute threshold and the just noticeable difference
Light sensitive tissue lining the back of the eyeball
The process by which the eye maintains a clear image on the retina
Photoreceptors that detect color, operate under normal daylight conditions and allow us to focus on fine detail
Photoreceptors that become active under low-light conditions for night vision
How do eyeglasses actually correct vision?
They provide an additional lens to help focus light more appropriately.
What are the differences between rods and cones?
There's 6 million cones compared to 120 million cones
The rods are distributed evenly except in the center, while cones are in the center and sparsely spread throughout the rest of the eye
An area of the retina where vision. Is the clearest and there are no rods at all
A location in the visual field that produces no sensation on the retina
If rods and cones are functioning then
You see in color, if just rods you see on a grayscale
Color opponent system
Pairs of visual neurons that work in opposition
The part of the Occipital lobe that contains the primary visual cortex
What happens when the cones in your eyes get fatigued?
If you stare at green long enough the green receiving cone will get tired. Staring at a white paper will make it appear red tinted because the still fresh red receptor is so much stronger
What is the relationship between the right and left eyes, and the right and left visual fields?
Half the axons in the optic nerve that leave each eye come from retinal ganglion cells (RCGs) that code info in the right visual field, whereas the other half code information in the left visual field
Visual form agnosia
The inability to recognize objects by sight
What are the main jobs of the ventral and dorsal streams?
ventral: travel across Occipital lobe into the lower levels of the temporal lobes and includes brain areas that represent an object's shape and identity.
Dorsal: Travels up from the Occipital lobe to the parental lobes, connecting with brain areas that identify the location and. Motion of an object
The retina contains several layers and the outermost consists of
Retinal ganglion cells (RGCs) that collect and send signals to the brain . Bundles of RGCs form the optic nerve
Information encoded by the retina travels to the brain along
The optic nerve, which connects to the lateral geniculate nucleus in the Thalamus and then to the primary visual cortex, area V1, in the Occipital lobe
Light striking the retina causes a specific pattern of response in each of the three cone types that are critical to color perception:
Short wavelength: bluish light
Medium wavelength: greenish light
Long wavelength: reddish light
The overall patter of the response across the three cone types results in a unique code for each color
Light passes through several layers in the eyes to reach the
Two types of photoreceptor cells in the retina
Transduce light into neural impulses: cones and rods
Two functionally distinct pathways project from
The Occipital lobe to visual areas in other parts of the brain
The ventral stream travels into the
lower levels of the temporal lobes and includes brain areas that represent an object's shape and identity
The Dorsal stream goes from the
Occipital lobes to the parental lobes, connecting with brain areas that identify the location and motion of an object
How features are linked together so that we see unified objects in our visual world rather than free-floating or miscombined features
A perceptual mistake where features from multiple objects are incorrectly combined
The idea that focused attention is not required to detect the individual features that comprise a stimulus, but is required to bind those individual features together
How does the study of illusory conjunctions help us understand the role of attention in feature binding?
Feature integration theory
A perceptual principle stating that even as aspects of sensory signals change perception remains consistent
How do we recognize our friends, even when they're hidden behind sunglasses?
The brain responds to the change as a new deviation of a regular thing instead of an entirely foreign object.
Gestalt psychology's perception grouping rules
Perception grouping rule of simplicity
The simplest answer is the best one
When confronted with 2 or more possible interpretations of an object's shape the visual system tends to select the simplest or most likely interpretation
Perception grouping rule of closure
We tend to fill in missing elements of a visual scene, allowing us to perceive edges that are separated by gaps as belonging to complete objects
Perception grouping rule of continuity
Edges or contours that have the same orientation have what the Gestalt psychologists called good continuation, and we tend to group them together perceptually
Perception grouping rule of similarity
Regions that are similar in color, lightness, shape or texture are perceived as belonging to the same object
Perception grouping rule of proximity
Objects that are close together tend to be grouped together
Perception grouping rule of common fate
Elements of a visual image that move together are perceived as parts of a single moving object
A mental representation that can be directly compared to a viewed shape in the retinal image
Monocular depth cues
Aspects of a scene that yield information about depth when viewed with only one eye
Types of Monocular depth cue
Linear perspective Monocular depth cue
When parallel lines seem to converge as they recede into the distance
Texture gradient Monocular depth cue
When you view a more or less uniformly patterned surface because the size of the pattern elements, as well as the distance between them, grows smaller as the surface recedes from the observer
Interpositions Monocular depth cue
When one object partly blocks another. You can infer that the blocking object is closer than the blocked object. However Interpositions by itself cannot provide info about how far apart the two objects are
The difference in the retinal images of the two eyes that provides information about depth
The perception of movement as a result of alternating signals appearing in rapid succession in different location
When people fail to detect changes to the visual details of a scene
A failure to perceive objects that are not the focus of attention
How can flashing lights on a casino sign give the impression of movement?
How can a failure focused attention explain change blindness?
Image based and parts based theories each
Explain some, but not all, features of object recognition
We experience a sense of motion through
The differences in the strengths of output from motion-sensitive neurons. These processes can give rise to illusions such as apparent motion
Depth perception depends on
Motion based cues which are based on the movement of the head over time
Change blindness and inattentional blindness occur when we
Fail to notice visible and even salient features of our environment, emphasizing that our conscious visual experience depends on focused attention
Illusory conjunctions occur when
Features from separate objects are mistakenly combined
According to feature-integration theory
Attention provides the glue necessary to bind features together.
The parental lobe is important for attention and contributes to feature binding
Some regions in the Occipital and temporal lobes
respond selectively to specific object categories, supporting the modular view that specialized brain areas represent particular classes of objects such as faces or houses or body parts
The principle of perceptual constancy holds that
Even as sensory signals change, perception remains consistent.
Gestalt principles or perceptual grouping
Govern how the features and regions of things fit together