Sensation and Perception Chapter 5

principle of proximity

Can also be called the principle of nearness. gestalt psychologists. things that are near each other appear to be grouped together.

border ownership

Ex: when two faces are seen as the figure, the border separating the blue faces from the grey background belongs to the faces. When perception shifts so the vase is the perceived figure, the border ownership shifts as well, so now the border belongs to the face.

likelihood principle

Helmholtz. corollary of the theory of unconscious inference. this states that we perceive the object that is most likely to have caused the pattern of stimuli we have received.conclusions can be based on a number of factors: similarity ( shapes are same color so likely it is same object), good continuation, or image resembles something we have seen before.

semantic encoding

Thomas Naselaris. Second method for analyzing patterns of voxel activation. this is based on the relationship between voxel activation and the meaning or category of each scene. Large number of images classified into categories. Then pattern of voxel activation and image category is determined. this makes it possible to use voxel responses from viewing a scene to make predictions about the type of scene the subject is viewing

regularities in the environment

characteristics of the environment (blue sky, green grass).

Wholes were in, sensations were out

gestalt psychologists

reversible figure-ground

gestalt psychologists studied the properties of figure and ground by considering patterns by Danish psychologist Edgar Rubin in 1915. The vase, can be perceived alternately either as two dark blue faces looking at each other, in front of a grey background, or as a grey vase on a dark blue background.

perceptual segregation

gestalt psychologists were interested determining characteristics of the environment responsible for this. The perceptual separation of one object from another.

stroboscope

mechanical device that created an illusion of movement by rapidly alternating to slightly different pictures.

principle of uniform connectedness

modern perceptual psychologists. a connected region of the same visual properties, such as lightness, color, texture, or motion, is perceived as a single unit.

principle of common region

modern perceptual psychologists. elements that are within the same region of space appear to be grouped together. Ex: even though the circles inside the ovals are farther apart than the circles that are next to each other in neighboring ovals, we see the circles inside the ovals as belonging together. In this example, common region overpowers proximity, because proximity would predict that the nearby circles would be perceived together.

problem of hidden objects

occurs any time one object obscures any part of another object.

binocular fusion

our two eyes receive slightly different images because the eyes are in two slightly different locations. however, these two images are similar enough so they can be combined into a single perception by the brain. this is the process of combining these images.

persistence of vision

perception of a visual stimulus continues for about 250 ms after the stimulus is extinguished. thus, a picture that is presented for 100 ms will be perceived as lasting about 350 ms. Can be eliminated by presenting a visual masking stimulus.

light-from-above-assumption

physical regularity. the assumption that light is coming from above, because most light in our environment comes from above

li fei-fei

presented pictures of scenes with exposures ranging from 27 ms to 500 ms and asked observers to write a description of what they saw. (phenomenological method). She used a procedure called (masking) to be sure observers saw the pictures for exactly the desired duration. Found that the overall gist of a scene is perceived first, followed by perception of details and smaller objects within the scene.

apparent movement

principle behind the illusion of movement created by the stroboscope. Although movement is perceived, nothing is actually moving. Three components to stimuli that create apparent movement:1. one image flashes on and off, 2. period of darkness lasting a fraction of a second, 3. the second image flashes on and off. Wertheimer drew two conclusions to apparent movement: apparent movement cannot be explained by sensations, because there is nothing in the dark space between the flashing images- the whole is different than the sum of its parts, because the perceptual system creates the perception of movement where there actually is none.

perceptual organization

process by which elements in the environment become perceptually grouped to create our perception of objects. Incoming stimulation is organized into coherent units such as objects. Involves two components: grouping and segregation.

grouping

process by which visual events are "put together" into units or objects. Works in conjunction with segregation.

segregation

process of separating one area or object from another. seeing two buildings as separated from one another, with borders indicating where one building ends and the other begins.

physical regularities

regularly occurring physical properties of the environment. more vertical and horizontal orientations than oblique (slanted) in the environment. Objects in the environment often have homogeneous colors and nearby objects have different colors, so if we pick a point on a scene and move slightly away from that point (object is the same if color is same: object different if color is different).

semantic regularities

semantics-meanings of words or sentences. applied to perceiving scenes, semantics refers to the meaning of a scene. often related to the function of a scene, what happens within it. Ex: Food, cooking-kitchen. these are the characteristics associated with the functions carried out in different types of scenes. we use our knowledge of things (kitchens) to help perceive the briefly flashed loaf of bread. Also illustrated in "the multiple personalities of a blob"-blob is perceived as different objects depending on its orientation and the context within which it is seen.

Mary Potter

showed observers a target picture, then asked them if they saw that picture in a sequence of 16 rapidly presented pictures. Almost 100% accuracy, 90% when the target picture was only specified by a written description.

Grill-Spector experiment

shows that neural activity that occurs as a person is looking at a stimulus is related to that person's ability to identify the stimulus. A large neural response is associated with processing that results in the ability to (identify) the stimulus; a smaller response (detecting) the stimulus; and the absence of a response with missing the stimulus all together. This experiment is important because it shows that how the brain reacts to a stimulus (as it is being presented) determines our ability to identify the stimulus.

voxel

small cube-shaped area of the brain about 2 or 3 mm on each side. The size of this depends on the resolution of the fMRI scanner.

theory of unconscious inference

some of our perceptions are the result of unconscious assumptions we make about the environment. this was proposed to account for our ability to create perceptions from stimulus information that can be seen in more than one way.

inverse projection problem

task of determining the object responsible for a particular image on the retina. It involves starting with the retinal image and extending rays out from the eye. The image on the retina is ambiguous.

viewpoint invariance

the ability to recognize an object seen from different viewpoints. Enables people to tell whether faces seen from different angles are the same person, this task is difficult for computers.

properties of the figure and ground

1. the figure is more thinglike and more memorable than ground. When you see a vase as a figure, it appears as an object that can be remembered later, but when you see the same light area as ground, it appears to be a background instead of an object, which is not memorable. 2. the figure is seen as being in front of the ground ex: when vase is the figure is appears to be in front of the dark background, and when the faces are seen as figure, they are on top of the light background. 3. near the borders it shares with the figure, the ground is seen as unformed material without a specific shape, and seems to extend behind the figure. But, grounds do not lack shape entirely; thus they are often shaped by borders distant from those they share with the figure. 4. the border separating the figure from the ground appears to belong to the figure. Ex: when two faces are seen as the figure, the border separating the blue faces from the grey background belongs to the faces.

illusory contours

A demonstration that argues against sensations. When there is no physical edges present but there is a perception of a triangle. Sensations cannot explain this because there aren't any sensations along the contours.

gestalt psychologists

Answer the question of what causes some elements to become grouped so they are part of one object. Gestalt is roughly translated as meaning configuration. They asked "how are configurations formed from smaller elements?".

structuralism

Approach that came before gestalt psychology, proposed by Wilhelm Wundt, who established the first laboratory of scientific psychology. This distinguishes between sensations- elementary processes that occur due to stimulation of the senses- and perceptions- more complex conscious experiences such as our awareness of objects. They saw sensations as being like the atoms of chemistry. Just as atoms combine, sensations combine to create complex perceptions. Another principle of this is that the combination of sensations to form perceptions is aided by the observer's past experiences. gestalt psychologists rejected this idea.

global image features

Aude Olivia and Antonio Torralba. Observers use this kind of information which can be perceived rapidly and are associated with specific types of scenes.

gist of a scene

When you can identify most scenes after viewing them for only a fraction of a second, no matter the size and complexity. Ex: flipping t.v. channels, you can still grasp the meaning of each picture as it flashes by (car chase, quiz contestants), even though you may not be able to identify specific objects. Possible to perceive the gist of a scene within a fraction of a second.

structural encoding

Thomas Naselaris. first of two methods for analyzing the patterns of voxel activation recorded from visual areas of an observer's brain. based on the relationship between voxel activation and structural characteristics of a scene, such as lines, contrasts, shapes, and textures. decoder was calibrated by determining the voxel activation patterns generated by eight different orientations. presented a large number of images, and determined how a large number of voxels responded to specific features of each scene. then reversed and used the patterns of voxel responses to predict image features that subject was viewing. this does a good job matching the structure of a target image, but a poor job matching the meaning of the target image.

Bayesian inference

a statistical technique that modern psychologists have used to quantify the idea of inferential perception, that takes probabilities into account. Ex: want to know if it will rain tomorrow. if we know it rained today, this increases the chances that it will rain tomorrow. If it rains one day it is more likely to rain the next day. Applying this type of reasoning to perception, we can ask whether an object in a kitchen is a loaf of bread or a mailbox. It's more likely for the loaf of bread to be in a kitchen, so the perceptual system concludes that bread is present.

image-based factors that determine which area is the figure

gestalt psychologists. 1. areas lower in the field of view are more likely to be perceived as figure. This was confirmed by Shaun Vecera, who flashed stimuli for 150 ms and determined which area was seen as figure, the red or the green area. The results concluded that there is no left-right preference for determining figure, but there is a definite preference for seeing objects lower in the display as figure. In our normal experience, the "figure" is much more likely to be below the horizon. 2. figures are more likely to be perceived on the convex side of borders ( borders that bulge out). (Mary Peterson and Elizabeth Salvagio) to understand how segregation occurs we need to go beyond simply identifying factors like convexity. Segregation is determined not by just what is happening at a single border but by what is happening in the wider scene. This makes sense when we consider that perception generally occurs in the scenes that extend over a wide area.

organizing principles

gestalt psychologists. Perception depends on a number of these. These determine how elements in a scene become grouped together. The starting point for these principles are things that usually occur in the environment.

principle of similarity

gestalt psychologists. When most people perceive as either horizontal rows of circles, vertical columns of circles, or a square filled with evenly placed dots. But when change the color of some of the columns, most people perceive vertical columns of circles. Similar things appear to be grouped together. This law causes circles of the same color to be grouped together. This can also occur because of similarity of shape, size, or orientation. This also occurs for auditory stimuli. Ex: notes that have similar pitches and that follow each other closely in time can become grouped to form a melody.

principle of good continuation

gestalt psychologists. 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. This principle operates on smooth surfaces as well: objects that are partially covered by other objects are seen as continuing behind the covering object. Sharp turns usually violate this.

principle of common fate

gestalt psychologists. things that are moving in the same direction appear to be grouped together. Ex: Se big flock of birds as one unit., and if some birds start flying in another direction, this creates a new unit. This can work even if the objects in a group are dissimilar. The key to this is that a group of objects are moving in the same direction.

figure-ground segregation

gestalt psychologists. this problem is related to the question of what causes perceptual 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). Gestalt psychologists were interested in determining the properties of the figure and the ground and what cause us to perceive one area as a figure and the other as ground.

subjective factors that determine which area is figure

gestalt psychologists.1. (Wertheimer) W and M demonstration- the pattern with the two uprights is the dominant perception. Uprights are created by the principle of good continuation, and that this principle overrides any effects of past experience due to having seen Ws or Ms before 2. (Gibson and Peterson) meaningfulness can influence the assignment of an area as figure means that the process of recognition must be occurring either before or at the same time as the figure is being separated from the ground. This idea debunks gestalts thoughts on the fact that the figure must stand out from the ground before it can be recognized. 3. When it is initially difficult to perceive figures hidden in the scene: Change from seeing rocks to being able to see faces is a change in the perceptual organization. The two shapes that you first perceive as two separate rocks in the stream become perceptually grouped together when they become the left and right eyes of a face. Once you perceive a particular grouping of rocks as a face, it is often difficult not to perceive them in this way- they have become permanently organized into a face.

degree of openness

global image feature. Olivia and Torralba. Open scenes, such as the ocean, often have a visible horizon line and contain few objects. Street scene is also open, just not as much as the ocean scene. Forest has a low degree of openness.

degree of naturalness

global image feature. Olivia and Torralba. natural scenes (ocean and forest), have textured zones and undulating contours. Man-made scenes, such as the street, are dominated by straight lines, horizontals, and verticals.

degree of roughness

global image feature. Olivia and Torralba. smooth scenes (low roughness) that contain fewer small elements (ocean). Scenes with high roughness (forest) contain many small elements and are more complex.

color

global image feature. Olivia and Torralba. some scenes have characteristic colors, ocean -blue, forest-green.

degree of expansion

global image feature. convergence of parallel lines (looking down a railroad track) that appear to vanish in the distance. this feature is especially dependent on the observer's viewpoint.

global image features

holistic and rapidly perceived.properties of the scene as a whole and do not depend on time-consuming processes such as perceiving small details, recognizing individual objects, or separating one object from another. contain information about a scene's structure and spatial layout. help explain how we can perceive the gist of scenes based on features that can be seen in brief exposures. Also illustrate the following general property of perception: past experience in perceiving properties of the environment play a role in determining our perceptions. Ex: sky-blue, grass-green, buildings-vertical.

binocular rivalry

if each eye receives totally different images, the brain can't fuse the two images. this condition is when the observer perceives wither the left-eye image or the right-eye image, but not both at the same time. This has been used to connect perception and neural responding in humans using an fMRI.

visual masking stimulus

this can eliminate the persistence of vision. It is usually a random pattern that covers the original stimulus, so if a picture is flashed for 100 ms followed immediately by a masking stimulus, the picture is visible for just 100 ms. This is often presented immediately after a test stimulus to stop the persistence of vision from increasing the duration of the test stimulus.

principle of pragnanz

this is also called, principle of good figure, or principle of simplicity. Central principle of gestalt psychology: every stimulus pattern is seen in such a way that the resulting structure is as simple as possible. Ex: the Olympic symbol, we see the display as five circles and not as a larger number of more complicated shapes. This will create the perception of smoothly curving lines.

scene

view of a real-world environment that contains (1) background elements and (2) multiple objects that are organized in a meaningful way relative to each other and the background. one way of distinguishing between objects and scenes is that objects are compact and are (acted upon), whereas scenes are extended in space and are (acted within). Ex: if we are walking down the street and mail a letter, we would be (acting upon) the mailbox (an object) and acting within the street (the scene)

erroneous perception

when viewing an object looks different from different angles. Most of the time this doesn't occur because the visual system solves the inverse projection problem and determines which object out of all the possible objects is responsible for a particular image on the retina.