Chapter 4.1 Flashcards
Sensation
-detection of a physical energy by sense organs
-sense organs send info to the brain
Perception
-the brains interpretation of raw sensory outputs
Illusion
-perception in which the way we perceive a stimulus doesn’t match its physical reality
Filling-In
-brain reconstructing things to show us stuff that isn’t really there
-can help us make sense or fool us instead
Transduction
-process of converting an external energy or substance into electrical activity within neurons
-done by sensory receptors in response to stimuli
Sense Receptor
-responsible for transduction for a specific sensory system
-have receptors rather than dendrites
Sensory Adaptation
-process in which activation is greatest when a stimulus is first detected
-a gradual decline in sensitivity due to prolonged stimulation/exposure
-keeps us attuned to changes rather than constants
-ie. your own house smell
Psychophysics
-the study of how we perceive sensory stimuli based on their physical characteristics
-produced from Gustav Fechner (1860) who was the first to describe the things required for sensation (stimulus)
Absolute Threshold
-the lowest level of a stimulus needed for the nervous system to detect a change on 50% of trials
-when no other stimuli of the same type are present
-nothing vs. something
Just Noticeable Difference (JND)
-the smallest change in the intensity of a stimulus that we can detect
-aka difference threshold
-ie. 6 lb weight in one hand and 5 lb in the other; is there a noticeable difference?
Weber’s Law
-there is a constant proportional relationship between JND and the original stimulus intensity
-a certain difference needed for us to tell things apart
-measured in %
-aka the stronger the stimulus, the bigger the change needed for it to be noticeable
Weber Fraction
-the constant proportion of Weber’s Law
-differs depending on sensory input
Signal Detection Theory
-theory regarding how stimuli are detected under different conditions
-accounts for expectations, consequences, response requirements
Signal Detection Expiriment
Components:
1. on 1/2 of the trials, one low intensity stimulus is presented
2. on 1/2 of the trials, no stimulus is presented
-trials are randomized so the subject cannot predict outcomes
Signal-to-noise Ratio
-it is harder to detect a signal as background noise increases
Signal Detection: Hit
-subject detects a stimulus that was present
Signal Detection: Miss
-subject fails to detect a stimulus that was present
Signal Detection: False Alarm
-subject indicates a stimulus was present when it was not
Signal Detection: Correct Rejection
-subject indicates there was no stimulus when there was no stimulus
Doctrine of Specific Nerve Energies
-1826: Johannes Müller
-says that even though there are many stimulus energies (light, sound, touch), the sensation we experience is determined by the sense receptor, not the stimulus
-ie. Phosphenes
Phosphenes
-vivid sensations of the light cause by pressure on eye’s receptor cells
-occur due to brain reacting the same way to light and touch perception
Cross-Modal Processing
-processing of signals from one sense in another sensory area
McGurk Effect
-when processing speech brain calculates most probable sound from given vision and audition info
-mismatch between what is seen and what is heard
-ie. ba vs. fa
Synesthesia
-a condition in which people experience cross-modal sensations
-over 60 types identified
Grapheme-Colour Synesthesia
-most common type of synesthesia
-person’s experience of numbers and letters are associated with the experience of colour
Other types of synesthesia???? pg 124
The Role of Attention
-attention and perception interact
-focus our attention on certain stimuli in our environment
-sometimes we exclude other information
Selective Attention
-process of selecting one sensory channel and ignoring or minimizing others
-involved reticular activating system (RAS) of the forebrain
Dichotic Listening
-used to study selective attention
-people hear two different messages, one in each ear, and ask them to ignore a message in one ear
-subject knew little or nothing about the messages as a result
Cocktail Party Effect
-our ability to pick out important messages in a conversation that doesn’t involve us
-not explained by selective attention
-ie. our name
Inattentional Blindness
-failure to detect stimuli that are in plain sight when our attention is focused elsewhere
-ie. gorilla suit during game of pass video
The Binding Problem
-a great mystery of psychology
-different aspects of a stimulus are processed in a different part of our brain
-we perceive the stimulus as a single unit
-pieces are bound together seamlessly
Parallel Processing
-ability to attend to many sense modalities simultaneously
Bottom-up Processing
-processing in which a whole stimulus is constructed from parts
-stimulus driven
Top-down Processing
-conceptually driven processing influenced by beliefs and expectancies
Perceptual Hypotheses
-educated guesses about what our sensory system tells us
-sometimes correct
Perceptual Set
-set formed when expectations influence perceptions
-and example of top-down processing
Perceptual Constancy
-the process by which we perceive stimuli consistently across varied conditions
-3 types
Shape Constancy (1/3)
-how we see shapes
-ie. 3 doors and we see one shut, open, and halfway open
Size Constancy (2/3)
-our ability to perceive objects as the same size no matter their distance from us
-ie. when someone walks away from you, you don’t think they are shrinking
Colour Constancy (3/3)
-our ability to perceive colour consistently across different levels of lighting
Gestalt Principles
-rules that govern how we perceive objects as a whole within their context
Subjective Contours
-when our brains provide missing info about outlines
Proximity (gestalt principles)
-objects close together are perceived as unified wholes
Similarity (gestalt principles)
-we see similar objects as comprising a whole, over dissimilar objects
Continuity (gestalt principles)
-still perceiving objects as a whole even if other objects block part of them
Closure (gestalt principles)
-when partial visual info is present our brains fill in the missing pieces
-similar to subjective contours
Symmetry (gestalt principles)
-perceive objects that are symmetrically arranged as wholes more often than those that aren’t
Figure-ground (gestalt principles)
-we make an instantaneous decision to focus on what we believe is the central figure
-ignore what we believe to be the background
-ie. vase vs. two faces
Perceiving Motion
-we determine movement by comparing visual frames momentarily
Motion Blindness
-can’t string images together to allow detection of motion
Phi Phenomenon
-the illusory perception of movement produced by the successive flashing of images
Apparent Motion
-when stimuli flash in different locations next to each other and movement is perceived
Face Perception
-may be something we are born with
-2-3 week old babies can imitate face expressions
Prosopagnosia
-face blindness
-need to look at cues to recognize people
-deficit in fusiform gyrus
Depth Perception
-ability to judge distance and 3D relations
Monocular Depth Cues
-stimuli that enable us to judge using only one eye
Motion Parallax
-monocular cue
-ability to judge the distance of moving objects from their speed
Pictorial Depth Cues
-monocular cue
-clues about distance in a flat picture
-many factors
Relative Size (Pictorial Cues)
-more distant objects look smaller than closer objects
Texture Gradient (Pictorial Cues)
-texture becomes less apparent as objects move farther away
Interposition (Pictorial Cues)
-closer object blocks the view of object behind it
Linear Perspective (Pictorial Cues)
-outlines of objects converge as distance increases
-vanishing point: where lines appear to meet
Height in plane (Pictorial Cues)
-distant objects appear higher and closer ones appear lower
Light and shadow (Pictorial Cues)
-objects cast shadows that give us a sense of their 3D form
Binocular Depth Cues
-stimuli that enable us to judge using both eyes
-2 main depth cues
Retinal Disparity
-binocular depth cue
-objects project images to slightly different locations on R and L retinas
-each eye sees a different view of the object
Binocular Convergence
-binocular depth cue
-sensing the eyes move closer together as they focus on closer objects
Auditory Localization
-locating the source of a sound in space
-intensity and timing of the sound arriving at the ear are factors that assist
Subliminal Perception
-registration of sensory input without conscious awareness
Subliminal Persuasion
-sub threshold influences our behaviour
-no evidence of lasting effect
