Chapter 5 Flashcards
Why is the perceptual system not concerned with determining an object’s image on the retina?
It’s job is to determine the object out there that created the image
What is the inverse projection problem?
The task of determining the object responsible for a particular image on the retina.
What problems do computers face in object recognition that the human brain is able to do flawlessly?
1) objects are hidden or blurred
- computers have a hard time recognizing partially hidden objects or blurred objects such as faces, while the brain will still be able to make the connection and recognize things.
2)Different viewpoints
- objects can be viewed from all kinds of viewpoints and they look slightly different in every single one of them. It’s not obvious to a computer.
What is viewpoint invariance?
The ability to recognize an object seen from different viewpoints.
Describe perceptual organization.
Process by which elements in a person’s visual field become perceptually grouped and segregated to create a perception.
Incoming stimulation is organized into coherent units such as objects.
Involve two components
- grouping
- segregation
What is grouping in perceptual organization?
Process by which elements in a visual scene are “put together” into coherent units or objects. Ex: going to new york city and your brain is able to group the visual elements to create each building.
What is segregation in perceptual organization?
Works in conjunction with grouping
Process of separating one area or object from another. Ex: seeing two buildings as separate buildings, with borders indicating where they end.
What is the Gestalt approach to perceptual grouping of Gestalt psychologists?
We can understand the Gestalt approach by first considering an approach called structuralism
Structuralism = distinguishes sensations and perceptions. Sensations as analogous to the atoms of chemistry. Just as atoms combine to create complex molecular structures, sensations combine to create complex perceptions.
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V
Rejected by Gestalt psychologists.
Apparent movement
- illusion of movement by rapidly alternating two slightly different pictures —> How the structuralist’s idea that experience is created by sensations could explain the illusion of movement he observed.
What are the three components of apparent movement?
1) one light flashes
2) There is a period of darkness lasting a fraction of a second
3) The second image flashes
Why don’t we see the darkness in the period of darkness in between two images in apparent movement?
Because our perceptual system adds something during the period of darkness — the perception of an image moving through the space between the flashing lights
What were Wertheimer’s two conclusions from the phenomenon of apparent movement?
1) apparent movement can’t be explained by sensations alone, because there is nothing in the dark space between the flashing lights
2) the whole is different than the sum of its parts, because the perceptual system creates the perception of movement where there actually is none
What are illusory contours?
A shape seemingly created by other shapes with no physical edges present.
Cannot be explained by sensations because there aren’t any sensations along the contours.
What is the proposition of Gestalt psychologists?
Proposed that perception depends on a number of principles of perceptual organization, which determine how elements in a scene become grouped together.
What are the starting points for the principles of organization of Gestalt psychologists?
Things that usually occur in the environment.
Ex: perceive one rope in multiple ropes
This gives to Gestalt’s idea of the principle of good continuation
What is the principle of good continuation?
Points that, when connected, result in straight or smoothly curving lines are seen as belonging together, and the lines tend to be seen in such a way as to follow the smoothest path.
Objects that are partially covered by other objects are seen as continuing behind the covering object.
What is the principle of pragnanz also called the principle of good figure or principle of simplicity?
Every stimulus pattern is seen in such a way that the resulting structure is as simple as possible.
Ex: symbol of the olympics
What is the principle of similarity?
Similar things appear to be grouped together.
Ex: causes circles of the same colour to be grouped together.
Also works for auditory stimuli. Notes of same pitch that follow each other closely in time can become perceptually grouped to form a melody.
What is the principle of proximity or nearness?
Things that are near each other appear to be grouped together
What is the principle of common fate?
Things that are moving in the same direction appear to be grouped together.
Ex: flock of birds all flying together. Flock as a unit.
Also to changes in illumination when elements of our visual field that become lighter or darker simultaneously are perceived as being grouped into a unit
What is the principle of common region?
Elements that are within the same region of space appear to be grouped together.
Ex: things inside ovals will seem to belong together
What is the principle of uniform connectedness?
A connected region of the sale visual properties, such as lightness, colour, texture, or morion, is perceived as a single unit.
Ex: connectedness overpowers proximity —> ovals with circles in them example.
Why are the Gestalt principles still important even if we consider them obvious?
They are the basic operating characteristics of our visual system that determine how our perceptual system organizes elements of the environment into larger units.
What is the approach to studying perceptual segregation by considering the figure-ground segregation?
When we see a separate object, it is usually seen as a figure that stands out from its background, which is called the ground.
Ex: paper on a desk. Surface of desk as ground and paper as figure. If you step backwards you might see the desk as the figure and the wall as the ground.
What is the reversible figure-ground?
It can be perceived alternately either as two dark blue faces looking at each other, in front of a gray background, or as a gray vase on a dark blue background.
What are some of the properties of the figure and ground?
1) figure is more thinglike and more memorable than the ground. Seen as being in front if ground. When the ground is seen as the figure, the rest is seen as the background.
2) ground seen as unformed material, without specific shape.
3) border separating figure from ground appears to belong to the figure. Called border ownership
What is border ownershiip?
Border belonging to one area
What are the Gestalt figural cues?
They determine how an image is segregated into figure and ground.
1) areas lower in the field of view are more likely to be perceived as figure
2) figures are more likely to be perceived on the convex side of borders
How did Gibson and Peterson show that figure-ground formation can be affected by the meaningfulness of a stimulus?
A display can be perceived in two ways. Experiences do shape perception a bit
What is the recognition by components theory?
States that objects are comprised of individual geometric components called geons and we recognize objects based in the arrangement of those geons.
What are geons?
Three-dimensional shapes like pyramids, cubes, cylinders.
Building blocks of objects and the same geons can be arranged in different ways to form different objects.
What is a scene?
View if a real-world environment that contains background elements and multiple objects that are organized in a meaningful way relative to each other and the background
How do we distinguish between objects and scenes?
Objects are compact and are acted upon.
Scenes are extended in space and are acted within
What is the gist of a scene?
The general description of the type of scene, the identification of important properties of most scenes after viewing them for only a fraction of a second.
What is the phenomenon called persistence of vision?
The perception of a visual stimulus continues for about 250 ms (1/4 second) after the stimulus is extinguished.
What enables observers to perceive the gist of a scene so rapidly?
Global image features
- type of information that can be perceived rapidly and are associated with specific types of scenes.
What are some of the global image features?
1) Degree of naturalness
- Natural scenes, like forest or ocean
- they have textured zones and undulating contours.
- Man made scenes are dominated by straight lines and horizontals and verticals
2) Degree of openness
- open scenes, like the ocean, often has a visible horizon line and contain few objects.
- street scene is also open, but not as much as ocean
- forest = low degree of openness
3) Degree of roughness
- smooth scenes like the ocean contain fewer small elements
- scenes with high roughness like the forest contain many small elements and are more complex.
4) Degree of expansion
- convergence of parallel lines, indicates a high degree of expansion. Ex: looking down railroad tracks that appear to vanish into the distance.
5) Colour
- some scenes have characteristic colours, like the ocean (blue) and the forest (green and brown)
What are regularities in the environment?
Characteristics of the environment that occurs frequently.
What are physical regularities?
Regularly ocurring physical properties of the environment
What is the light from above assumption?
We usually assume that light is coming from above, because light in the environment, including the sun and most artificial light, usually comes from above.
What are semantics in scenes?
It refers to the meaning of a scene.
What are semantic regularities?
The characteristics associated with activities that are common in different types of scenes.
What does the RBC theory lack?
It doesn’t account for grouping or organization like the Gestalt principles do, and some objects simply can’t be represented by assemblies of geons (like clouds in the sky that typically don’t have geometric components)
It also doesn’t allow for distinguishing between objects within a given category, such as two types of coffee mugs or species of birds that might be composed of the same basic shapes.
What is a scene schema?
The knowledge of what a given scene typically contains.
What is Helmholtz’s theory of unconscious inference?
Based on the realization that the image on the retina is ambiguous.
The judgment of what is likely to occur, called the likelihood principle, by a process called unconscious inference, in which our perceptions are the result of unconscious assumptions, or inferences we make about the environment.
What is the likelihood principle?
We perceive the object that is most likely to have caused the pattern of stimuli we have received.
What has Helmholtz’s theory of unconscious inference been reconceptualized as?
PREDICTION
What is prediction?
The idea that our past experiences help us make informed guesses about what we will perceive
What is the Bayesian inference?
Our estimate of the probability of an outcome is determined by two factors:
1) the prior probability, or simply the prior, which is our initial estimate if the probability of an outcome, and
2) the extent to which the available evidence is consistent with the outcome (LIKELIHOOD of the outcome)
Prior knowledge + likelihood that it will happen, influence perception
What is predictive coding?
A theory that describes how the brain uses our past experiences (priors) to predict what we will perceive.
Our brain’s predictions about the world are represented at higher levels of the visual system
When new incoming visual input reaches the receptors and is sent upward in the visual system, that signal is compared to the predictions flowing downward from higher levels.
How is predictive coding different from Helmholtz’s idea that we use our past experiences to make inferences about what we will perceive?
Predictive coding takes unconscious inference a step further by linking prediction to what is happening in the brain.
What is the use of the lateral occipital complex?
Active when a person views any kind of object (animal, face, house, tool), but not when they view a texture or an object with the parts scrambled
Activated regardless of size, orientation, position or other basic features
It builds upon the processing that took place in lower-level visual regions, like V1.
It does NOT differentiate between different TYPES of objects.
What is the fusiform face area and where is it located?
Located in fusiform gyrus on the underside of the brain directly belie inferotemporal cortex.
Malfunction of it causes prosopagnosia
What is prosopagnosia?
Damage to fusiform face area
Difficulty in recognizing faces of familiar people.
What is the extrastriate body area?
Specialized area in temporal cortex
Activated by pictures of bodies and parts of bodies
It is unrealistic to think that we would have a distinct brain area to represent every category of object that we encounter. What’s more likely?
That neural representation of objects is distributed across brain areas.
Which prt of the brain was found to respond to places?
Parahippocampal place area
What is important for the parahippocampal of place area?
Information about spatial layout, because increased activation occurs both to empty rooms and to rooms that are completely furnished.
What is the spatial layout hypothesis?
Proposes that the parahippocampal place area responds to surface geometry or geometric layout of a scene.
What is another theory about the place area of the brain?
Its goal is to represent three-dimensional space more generally, even if there is no scene
What is binocular rivalry?
The observer perceives either the left-eye image or the right-eye image, but not both at the same time
Condition
What were Frank Tong’s findings about the experiment with people with binocular rivalry?
Presenting a picture of a face on one eye and a picture of a house on other eye with coloured glasses.
Coloured glasses caused the face to be presented to the left eye and the house to the right eye.
When perceiving house —> activity
increased in PPA, decreased in FFA
When perceiving face —> increased in FFA, decreased in PPA
