Chapter 3 - Perception Flashcards
-Perception is:
- experience resulting from stimulation of the senses. Basic Concepts:
- perceptions can change based on added information
- involves a process like reasoning or problem solving
- perceptions occur in conjunction with actions
-It is possible that true human perceptual processes are
unique to humans
-Attempts to create artificial forms of perception (machines) have been met with limited success and each time have had problems that could not be solved
Why is it so Difficult to Design a Perceiving Machine?
-Inverse Projection Problem
- refers to the task of determining the object responsible for a particular image on the retina
- involves starting with the retinal image and then extending outward to the source of that image
-Objects can be hidden or blurred
-people can often identify objects that are obscured and therefore incomplete, or in some cases objects that are blurry
-Objects look different from different viewpoints
-viewpoint invariance
Approaches to Understand Perception
- Direct perception theories
- bottom-up processing
- perception comes from stimuli in the environment (starts form the “bottom”)
- parts are identified and put together, and then recognition occurs
- Construction perception theories
- top-down processing
- people actively construct perceptions using information based on expectations
- start from the “top” (brain)
The Complexity of Perception
-Bottom-up processing
- perception may start with the senses
- incoming raw data
- energy registering on receptors
Top-down processing
- perception may start with the brain
- person’s knowledge, experience, expectations
Hearing Words in a Sentence
-when you hear words in a sentence spoken or in a foreign language, your ability to pick out or understand words based on context demonstrates top-down processing (e.g., listening to a baseball game that is broadcast in Spanish may make it easier to hear players names or certain “baseball-related” words)
(speech segregation)
-the ability to tell when one-word ends, and another begins
-transitional Probabilities
the likelihood that one sound will follow another within a word
-Statistical probabilities
every language has transitional probabilities for different sounds, and the process of learning about transitional probabilities and about other characteristics of language
Experiencing Pain
-Direct Pathway Model
- an early model that emphasized nociceptors that would send pain messages directly to the brain
- A bottom-up processing model
- more recent models have found that expectations, attentions and distraction can affect how we experience pain in a “top-down” manner
- The placebo effect
- attention, play games during bandages change
Bottom-up Processing: Behavioral
-Recognition-by-components theory:
- we perceive objects be perceiving elementary features
- Geon’s: three-dimensional volumes
- objects are recognized when enough information is available to identify objects; geons
Geons
- discriminability: geons can be distinguished from other geons from almost all viewpoints
- resistance to visual noise: geons can be perceived in “noisy” conditions
- distinct: 36 different geons have been identified
Treisman’s Feature Integration theory (FIT) – COGLAB 3 – Illusory Conjunctions
-Visual perception and visual attention Identification of objects in the world involves two stages:
- A pre-attentive stage that automatically computes basic features
- An attentive stage that binds together the basic features to form objects Identification of objects depends on what else is also visible
-Visual search can be used for two basic purposes: First, to identify the basic features of visual perception that are proceeded pre-attentively. Second, to investigate the nature of attentive stage.
Feature integration theory (FIT)
- Pre-attentive stage
- Automatic
- No effort or attention
- Unaware of process
- Object analyzed into features
-R.M. – Ballint’s syndrome
- inability to focus attention on individual objects
- high number of illusory conjunctions reported
-Feature integration theory (FIT)
- mostly bottom-up processing
- top-down processing influences processing when participants are told what they would see
- top-down processing combines features with feature analysis to help one perceive things accurately
Helmholt’s Theory of Unconscious Inference (1860)
-Top-down theory
- some of our perceptions are the results of unconscious assumptions we make about the environment
- we use our knowledge to inform our perceptions
- We infer much of what we know about the world
-Likelihood principle:
we perceive the world in the way that is “most likely” based on our past experiences
-unconscious inference
our perception is the result of unconscious assumptions or inferences about our environment
Perceptual Organization
-explains the way elements are grouped together to create larger objects
-Old-view – structuralism
-perception involves adding up sensations
-“New” view – Gestalt psychologists
-the mind groups patterns according to laws of perceptual organization
COGLAB 4 – Apparent Motion
-Timing between the flashes was important
- short ISI (the interstimulus interval)
- two dots were presented simultaneously
- Long ISI
- two dots were presented alternatively
- Intermediate ISI
- perception of motion
- you should find that the best ISI increase with distance
- the relationships between spatial separation and ISI threshold are consistent with a variety of theories that hypothesize that the visual system builds a motion percept
- for larger separations, the stimulus must “move” a farther distance, which presumably requires a greater length of time
Theoretical importance - apparent motion
- perception involves a process of perceptual organization that required an understanding of the relationships between stimuli
- If perception involves simply detecting the properties of the physical world, one expects that the observer would either be able to detect the stimuli or not, but the percept is quite different: motion is observed, even though it is not a property of the stimuli
Gestalt Laws of Perceptual Organization
-Law of good continuation
-lines tend to be seen as following the smoothest path
-Law of pragnanz (simplicity or good feature)
-every stimulus pattern is seen so the resulting structure is as simple as possible
-Law of similarity
-similar things appear grouped together
Perceptual Organization
-Law of proximity
-things near to each other appear grouped together
-Law of common fate
-things moving in the same direction appear to be grouped together
-Gestalt laws often provide accurate information about
properties of the environment
- reflect experience
- experience is important but does not overcome perceptual principles
- Gestalt laws are intrinsic
Physical Regularities
-Oblique effect
-people can perceive verticals and horizontals more easily that other orientations
-Light-from-above assumption
- light comes from above
- is usually the case in the environment
- we perceive shadows as specific information about depth and distance
Semantic Regularities
- the measuring of a given scene is related to what is happening within the scene, and semantic regularities are the characteristics associated with the functions carried out in different types of scenes
- A scene schema is the knowledge of what a given scene ordinarily contains (e.g., if you think of a professor’s office, what would you expect to find/see there?)
- we know that characteristics associated with the functions carried out in different types of scenes
Bayesian Inference
-Thomas Bayes (1701-1761)
- One’s estimate of the probability of a given outcome is influenced by 2 factors:
- the prior probability (our initial belief about the probability of an outcome, hypothesis)
- the likelihood of an observation given the outcome (hypothesis)
- these factors set up an equation, seen below
Neurons and the Environment
- some neurons respond best to things that occur regularly in the environment
- neurons become tuned to respond best to what is we commonly experience
Movement Facilitates Perception
- movement helps us perceive things in our environment more accurately than static, still images
- for example, a horse in the distance standing still may be more difficult to discern that the horse walking across the field
- walking around that same horse to see it from different angles will also facilitate accurate perception
The Interaction of Perception and Action
-our actions within or upon the environment around us involve a constant stream of updating perceptions and recognition of very subtle changes
-What stream:
identifying an object (ventral pathway)
-Where stream:
identifying the objects location (dorsal pathway)
Perception and Action: Using Dissociation Logic
- if you are tying to understand a complex system, you can logically deduce conclusions from “malfunctions”
- damage to different areas of the brain cause very different deficits
- we can conclude that a specific area is necessary for a specific function
- Brain Ablation method allows scientists to damage specific areas of otherwise normal brains (usually in monkeys or cats)
- controlled damage allows for clear conclusions to be drawn
-perception pathway
path from the visual cortex to the temporal lobe (what)
-action pathway
visual cortex to the parietal lobe (where)
Single Dissociation
- one function is lost, another remains
- ex., monkey A has damage to temporal lobe. This monkey is no longer able to identify objects (what) but can still identify locations
- therefor, what and where rely on different mechanisms, although they may operate totally independent of one another
-Double dissociation
- requires two individuals with different damage and opposite deficits
- ex., monkey A with temporal lobe damage ha intact “where” but impaired “what”; monkey B with parietal lobe damage has intact “what” but impaired “where”
- therefore, what and where streams must have different mechanisms AND operate independently of one another
Mirror Neurons
-these neurons respond while a subject watches an action being performed in the same way as if the subject was performing the action
fMRI research has found evidence of a mirror neuron system in the brain
-Iacoboni (2005) found higher rate of mirroring if the subject’s intention to perform the action was greater
