Chapter 3: Perception Flashcards
Perception
the act of becoming aware of something through stimulation of the senses; pattern recognition
Pattern recognition
ability to detect meaningful patterns in the environment
Inverse projection problem
task of determining the object responsible for creating a particular image on the retina; starts with the retinal image then extending rays out from the eye
Viewpoint invariance
people’s ability to recognize an object even when it’s seen from different viewpoints or angles
2 types of information used by the human perceptual system
(1) environmental energy stimulating the receptors (2) knowledge and expectations that the observer brings to the situation
Size constancy
an object is the same size at different distances; it is just smaller on the retina when farther away
Bottom-up processing
basic elements come together until the mind reaches a higher level of understanding (e.g. an image generates electrical signals transmitted to the retina then to the brain’s visual receiving area)
Top-down processing
originates in the brain; prior knowledge or context are used to analyze incoming information to inform perception (e.g. perceiving objects in different scenes)
Speech segmentation
the ability to tell when one word in a conversation ends and when the next one begins
Transitional probabilities
likelihood that one sound will follow another within a word
Statistical learning (Saffran)
the process of learning about transitional probabilities and other characteristics of language; as early as 8 months old through passive learning
Helmholtz’ theory of unconscious inference
some of our perceptions are the result of unconscious assumptions we make about the environment
Likelihood principle
we perceive the world in the way that is most likely to have caused the pattern of stimuli we have received, based on our past experiences
6 Gestalt principles of perceptual organization
similarity, proximity, closure, common fate, symmetry, good continuation
Similarity principle
elements that look similar will be perceived as part of the same form or group
Proximity principle
elements that are close together will be perceived as a coherent group
Closure principle
humans tend to enclose spaces by completing an illusory contour and ignoring gaps in a picture
Common fate principle
If two or more objects are moving in the same direction and at the same speed, they tend to be perceived as a group
Symmetry principle
images that are perceived as symmetrical are perceived as belonging together
Good continuation principle
people tend to connect elements in a way that makes the elements seem continuous or flowing in a particular direction; objects that are overlapped by other objects are seen as continuing behind those objects
Bayesian inference
top-down process; our estimate of the probability of an outcome depends on its prior probability and the likelihood
Apparent movement (Wertheimer)
movement is perceived even though nothing is actually moving (e.g. rapidly alternating pictures)
3 components to stimuli that create apparent movement
(1) one light flashing on and off, (2) a period of darkness lasting a fraction of a second, (3) second light flashing on and off
2 conclusions from apparent movement
(1) it cannot be explained by sensations because there’s nothing in the dark space between flashing lights, (2) the whole is different than the sum of its parts, one of the basic principles of Gestalt psychology
Law of pragnanz/Principle of good figure or simplicity
every stimulus pattern is seen in such a way that the resulting structure is as simple as possible
Regularities in the environment
frequently occurring characteristics of the environment, either physical or semantic
Physical characteristics
regularly occurring physical properties of the environment (e.g. vertical and horizontal orientations)
Oblique (angled) effect
we perceive verticals and horizontals more easily than other orientations; can be explained by theory of natural selection
Light-from-above assumption
we assume that light comes from above because light in our environment usually comes from above; we perceive shadows as specific information about depth and distance
Semantic regularities
characteristics associated with the functions carried out in different types of scenes
Scene schema
knowledge of what a given scene typically contains that help us perceive them faster
Prior probability
our initial belief about the probability of an outcome
Likelihood
the extent to which the available evidence is consistent with the outcome
Brain ablation or lesioning
the study of the effect of removing parts of the brain in animals
Ventral stream
i.e. what or perception pathway; from the visual cortex to the temporal lobe
Dorsal stream
i.e. how or action pathway; from the visual cortex to the parietal lobe
Mirror neurons
neurons that respond both when a monkey observes someone else grasping an object and when the monkey itself grasps the same object; distributed throughout the brain in a network called mirror neuron system; involved with understanding intentions behind actions
Size-weight illusion
when a person is shown two similar objects (e.g. two cubes of same weight but different sizes), the bigger one is lighter than predicted
Inferotemporal cortex
in the front end of the ventral stream; has cells selective for object categories and some regions are selective for faces; view invariant
4 theories for bottom-up processing
distinctive features, recognition by components, template-matching, prototype
Distinctive features theory
all complex perceptual stimuli are composed of distinct features; pattern recognition is done by mentally assessing the presence or absence of a checklist of features
Recognition by components theory
pattern recognition done by identifying the building blocks that make up 3D objects; basic elements are composed of an alphabet of 36 primitive shapes called geons or geometric icons, which are compared to geon patterns stored in LTM and can be rotated in 3 dimensions
Template matching theory
we store an unlimited number of patterns corresponding to every object that we have experienced; a new instance is matched to the stored template
Limitations of template matching theory
impractical when the set of possible patterns is very large and inefficient because it fails to account for our ability to recognize new objects (w/o a stored template)
Prototype theory
we store the average or typical instance of the many different views of an object called a prototype (not a literal match)
Typical face processing
in a gestalt-like manner, using spatial relations among face parts to construct a holistic view
How do we process faces when they’re upside down?
we switch to noticing individual facial features or the component information instead of the holistic view; more common for non-faces
Feedforward process
mostly involved in bottom-up processing as information gets passe forward from one area to the next: V1 (primary visual cortex) to inferotemporal cortex
Primary visual cortex
where information from the eyes reach the cortex (in the occipital lobe) and the beginning of both the dorsal and ventral streams
Feedback process
mostly involved in top-down processing of face and object recognition as information gets passed backward from a higher level area to a lower level one: prefrontal cortex to V1
Importance of frontal lobe in face and object recognition
predicts its identity and helps finetune the representation in the inferotemporal cortex
Optic ataxia
a problem with visually-guided behavior stemming from impaired representations in the dorsal stream
Apperceptive agnosia
failure of perception in which some basic visual functions are preserved (e.g. acuity, color, motion) while others are disrupted; damage to the ventral stream
Associative agnosia
inability to recognize objects despite intact perception of basic visual characteristics, usually due to damage in the ventral stream
Gist perception
the abstract meaning of a scene is automatically extracted (~150 ms) based on little information; happens unconsciously
Scene layout perception
we can perceive the spatial layout of objects in a scene after a few seconds; repeated layouts are learned implicitly
Statistical estimation/Ensemble perception
the perceptual system can quickly extract ensemble properties in less than 50 ms when there are many objects e.g. mean size, orientation, velocity, direction
Pattern detection
perceptual system can detect trends or outliers in a graph; related to ensemble perception and gestalt grouping by proximity
