PSY280 - 1. Introduction Flashcards
Perceptual process
begins with stimulus + ends with conscious experiences of perceiving, recognizing + taking action
Bottom up processing/database processing
processing based on stimuli reaching receptors
based on incoming data - info at sense organs
data-driven
Top down processing/knowledge-based processing
knowledge-driven
high level of analysis, based on previous experience
processing based on knowledge
Psychological approach
psychophysics, measures relationship between stimuli and behavioral response
Physiological approach
measuring two relationships, relationship between stimuli and physiological responses and the relationship between physiological responses and behavioral responses
Cognitive influences on perception
How knowledge, memories + expectations that people bring to situation influence their perceptions
Principle of Representation
stimuli + responses created by stimuli transformed betw environmental stimulus + perception
light from the back, bounces off screen to our eyes, light is transformed by air, lighting conditions + anatomical structures of eye
projected to retina backward + upside down
change in info betw environmental stimuli + perception
Principle of Representation
perception not based on direct contact with stimuli
representations built based on activity at receptors that get integrated into the nervous system
using sensory info to make representations of world
Transduction
diff specialized neurons for every modality - take energy + turn it into electrical signals interpreted by your brain
transformation of one form of energy [light] to another form [electrical energy]
neural processing
starts at retina - start to organize info in the retina
some specialized for processing colour, some for contrast, shape
neural processing
gets more specific as passed through to the brain
ends up to the cortex eventually
Electrical signals enter vast interconnected network of neurons, first in retina + out back of eye and then in the brain
neural processing
multiple routes with some signals traveling in opposite directions some signals becoming reduced + others being amplified
changes in signals that occur as they are transmitted through this maze of neurons
Electrical signals arrive at primary receiving area
Primary receiving area for vision occupies most of the occipital lobe
Frontal lobe receives signals from all the senses and plays an important role in perceptions that involve the coordination of info received through two or more senses
Perception + Recognition
perception: organizing info, giving meaning
recognition: categorize stimuli
Action
how perception influences action + vice versa
perception doesn’t always create behavioural response
Electrical signals are transformed into conscious experience: person perceives that tree [5] and recognizes it [step 6]
Visual form agnosia: inability to recognize objects
Action: which involves motor activities
Perception
private experience, we can’t really know what they see
quelia (experience is different)
we are good at measuring our own perceptions
reliability in our measurements, consistency among our perceptual observations
data can scientifically validated
psychophysics
physical stimulus - psychological response
dominated by psychophysics: relationship betw physical stimulus + psychological response
psychophysics
physical component - wavelength
response - psychological component
how change in psychological response relates to physical change
Linear Relationship
as intensity increases, magnitude increases at same rate
Exponential Relationship
perception of magnitude increases slowly at beginning + exponentially later on
Logarithmic Relationship
dramatic increase at lower intensity, but at high intensity hard to tell difference
Intensity of Pressure vs. Pain
can tolerate pain to a certain point + jumps after the point of intolerable
at some point pain can be indicative of damage
absolute threshold
minimum stimulus intensity necessary for a stimulus to be detected
Development of the nervous system is influenced by kinds of stimuli have experienced in the environment
difference threshold
minimum difference that must exist between two stimuli before we can detect the difference
magnitude estimation
relationship between stimulus intensity + perceived magnitude •“On a scale of 1 to 10, how bright is A?”
Classical psychophysical Methods:
original methods used to measure relationship between stimuli and perception
perception is never perfect
humans are not ideal observers
there is uncertainty in perception system
it tends to be curve
absolute threshold in the middle, but it’s a fuzzy boundary
at 50% yes - follow line to intensity
Gustav Fechner
described methods for absolute threshold
linked perception to science
ebbinghouse: adapted it to memory, lead to cognitive psychology
method of limits
turn it down from top, start from bottom
experimenter present stimuli in either ascending or descending order
Threshold is determined by calculating the average of all crossover points
method of adjustment
have participant control it themselves - continuous stimulus
stimulus intensity is either increase or decrease until the stimulus can just be detected
method of constant stimuli
experimenter presents 5 to 9 stimuli with different intensities in random order
Threshold is defined as the intensity that results in detection on 50% of the trials
Method of constant some stimuli is most accurate method because it involves many observations + stimuli are presented in random order
Difference threshold
the smaller the diff, the harder it is to detect, but it depends on the starting point
Weber Fraction/Weber’s Law
weber percent is consistent
Ratio DL/standard for lifting weights is 0.02
Difference threshold for weight is about 2%
just noticeable difference (JND)
change in intensity between 25% “brighter” + 75% “brighter” (by convention). plotting percentage of times you are gonna say darker 50% is the reference point function of reference intensity
Magnitude estimation
Experiment your present to standard stimulus + assigned value
present lights at diff intensities + subject is asked to assign number to each of these lights proportional to the brightness of the original light
Magnitude estimation
Brightness/perceived magnitude is a perceptual measure that indicates what observer experiences
Response compression: increase in perceived magnitude is smaller than the increase in stimulus intensity
Expansion
as intensity is increased, perceptual magnitude increases more than intensity
Relationship between intensity of a stimulus in our perception follow same general equation of power functions
Stevens’ power law
P = KS^n
Perceived magnitude, P = constant, K x stimulus intensity, S raised to a power, n
Exponents < 1 = response compression + > 1 = response expansion
•n = exponent (slope of log)
JND
higher intensity, jnd increases more because it is a percentage
light intensity: dim light - little bit brighter, easy to notice
bright light - has to be much brighter to tell the difference
Weber’s Fraction
each type of sensory has diff weber fractions ∆I = k⋅I ∆I-JND k - WeberFraction I - referenceintensity
magnitude estimation
linear, exponential (response expansion), logarithmic (response compression)
compression: responses are compressed compared to intensity
expansion: as intensity increases, perceptual magnitude increases much more
power function
when you log each side the function is converted from non-linear to linear
exponent is slope
brightness: logarithmic function
