Problem 1 Flashcards
What is the Perceptual Process ?
The perceptual process begin with stimuli in the environment and ends with the behavioral responses of
- perceiving
- recognizing
- taking action
Principle of Transformation
Stimuli and the responses created by stimuli are transformed between environmental stimulus and perception
Eye’s optical system
- consists of the cornea + lens
–> they form a sharp picture of the stimulus on the receptors of the retina
Principle of representation
Everything a person perceives is based on representations of stimuli that are formed on the receptors and the activity in the persons NS
What are sensory receptors ?
Cells specialized to respond to environmental energy with each sensory systems receptors specialized to respond to a specific type of energy
ex.: visual receptors - light, auditory receptors - pressure changes in air
Function of Visual receptors
- Transforming environmental energy into electrical energy (Transduction)
- Shaping perception by the way they respond to stimuli
Transduction
Transformation of one form of energy to another form
Visual pigment
Light sensitive chemical that reacts to light
- found in visual receptors
- transforms light into electrical energy
- without it perception wouldn’t occur because the information about the representation of the stimulus in the retina wouldn’t reach the brain
Function of the network of neurons
- Transmits signals from receptors (retina) to the brain
- Changes these signals because there are multiple routes with signals
a) traveling in the opposite directions
b) being amplified
c) being reduced or prevented from entering
Primary receiving area
Receives signals from each sense
–> located in the cerebral cortex
Which lobe can you assign to which sense ?
Occipital lobe –> vision
Temporal lobe –> hearing
Parietal lobe –> touch
Frontal lobe –> all senses, plays important role in coordination of information received from 2 or more senses
Perception
Conscious awareness of the stimulus (active)
–> top down processing
Recognition
Placing an object in a category, that gives it meaning
Visual form of agnosia
Inability to recognize objects /
Perceiving parts of the object, but not being able to identify the whole object
Action
Refers to the mere act of looking at different parts of the stimulus, no need to interact with it
–> usually involves motor activities
Knowledge
Any information the perceiver brings to a situation
- -> can affect a number of steps in the perceptual process
- -> can be recently acquired information or acquired years ago
Bottom up processing
Processing, that is based on stimuli reaching the receptors
–> ‘incoming data’
Top down processing
Processing based on knowledge (Schemas)
Psychophysical approach/
Psychophysics
Measures the relationship between the stimuli and behavioral response
–> presenting a stimulus and determining the persons response
Oblique effect
There is a better detail vision for vertical and horizontal lines than slanted lines
Physiological approach
Measures the relationship between
- Physiological responses + stimuli
- Physiological responses + behavioral responses
–> used to understand the physiology behind the oblique effect
Absolute threshold
Describes the minimum stimulus intensity that can just be detected
ex.: Vision –> the smallest line that can barely be seen
–> threshold is lower (finer lines can be seen) when the lines are horizontal/vertical
Human perception is variable.
How can this affect measurements ?
Measurements at one point in time can differ slightly from measurements at another point.
Method of limits
(Classical psychophysical method)
Fechner
Experimenter presents stimuli by either ascending or descending order
- -> threshold is the average of all crossover points
- -> increasing or decreasing intensity
Crossoverpoint
The change/ Point when the observer goes from perceiving the stimulus to not perceiving it anymore or vice versa
ex.: hearing a sound –> not hearing it anymore
–> may vary slightly, procedure is therefore repeated
Method of adjustment
(Classical psychophysical method)
Fechner
Observer increases/decreases stimulus intensity until the stimulus can just be detected
–> fastest method because the observers can just adjust their threshold quickly
Method of constant stimuli
(Classical psychophysical method)
Fechner
Experimenter presents 5 to 9 stimuli with different intensities in a random order
–> threshold is the intensity that results in detection on 50% of the trials
–> most accurate method, but time consuming
Difference threshold
Describes the minimum difference that must exist between 2 stimuli before we can tell the difference between them
–> Differenze Limen (DL)
Weber fraction
The ratio of DL vs Standard always corresponds to a certain percentage
ex.: weight = 0.02
–> each type of sensory judgment has its own weber fraction
Weber law
The weber fraction remains the same as the standard is changed
ex.: if the weight is doubled, DL is doubled too
Magnitude estimation
Stevens
Measuring the relationship between the stimulus + perception of its magnitude
Response compression
Increase in perceived magnitude is smaller than the increase in stimulus intensity
ex.: doubling the intensity of brightness doesn’t necessarily double the perceived brightness
–> exponent < 1.0
Response expansion
As the intensity is increased, the perceptual magnitude increases more than the intensity
ex.: small increases in electric shock will result in large increases in pain
–> exponent > 1.0
Stevens Power law
Perceived magnitude = a constant x stimulus intensity , raised to a power
P = KS^n
Visual research
Method in which the observer has to find one stimulus among many, as quickly as possible
ex.: recognizing face in a crowd
Response criterion
Determines how and why we respond the way we do and therefore influences the threshold measurement
ex.: wanting to be totally sure before responding –> response is more conservative
–> every person has a different response criterion
Sensation
The act of unconsciously perceiving something (passive)
- -> bottom up processing
- -> step before actively perceiving
Electrophysiology
Presenting a stimulus and measuring the brain activity
–> done with animals
Neuropsychology
Studying the effects of brain damage in behavior
Which scanning techniques can be used to measure perception ?
- fMRI
- EEG
- TMS
Prosopagnosia (Face blindness)
Inability to recognize faces, but normal vision
–> lesion the ‘fusiform face area’ ( region of the IT cortex )
What are the basic stages of the ‘Perceptual process’ ?
- Environmental stimulus
- Light is reflected and transformed
- Receptor processes
- Neural processing
- Perception
- Recognition
- Action
Stage 1
Environmental stimulus
The person is observing the tree
Stage 2
Light is reflected and transformed
- Persons perception of the tree is based on the light reflected from the tree
- Eyes optical system transforms the stimulus into a sharp image on the receptors to the retina
Stage 3
Receptor processes
The visual receptors transform the environmental energy into electrical energy with the help of visual pigments
–> Transduction
Stage 4
Neural processing
- The tree is represented by electrical signals in the visual receptors
- Signals enter a complex network of neurons
- Signals then travel to brain
Stage 5
Perception
Electrical signals have reached the brain and are transformed into conscious experience
–> Person actively perceives the tree
Stage 6
Recognition
The person recognizes the stimulus, placing it into the category ‘tree’
Stage 7
Action
The person might then take action by merely looking at different parts of the tree / looking closer
When do the laws not apply ?
- Stevens law always applies
- Fechner’s law doesn’t when the exponent is > 1
- Webers law doesn’t when the exponent is < 1
