PSY368 Section 1 Flashcards
Background, Definitions, Psychophysics, Haptic Perception
Sensation (definition)
input about the physical world obtained by our sensory receptors
Perception (definition)
the process by which the brain selects, organizes, and interprets these sentations
The first contact between the organism and environment is known as
sensation
Transduction (definition)
the conversion of environmental energy into neural energy (energy from the environment activates receptors in our sensory systems)
Sensory transduction energy vs. sense
Light - vision
vibrations in air molecules - hearing
mechanical energy - touch
chemical energy - smell, taste
We can only perceive forms of energy that
can be transduced by our sensory systems
What is the stimulus for vision?
electromagnetic radiation
Wavelength (definition)
the distance between two consecutive peaks of a wave
The visual spectrum
~ 350 - ~700 nm
Perception is influenced by
memory, context, meaning, and experience
Perception is a function of
the neocortex
The neocortex can be referred to as
the interpretation machine
Relationship between action and perception
Perception guides action and action changes perspective (the perceptual cycle)
Psychophysical level of perception
the relationship between an attended stimulus and a person’s perceptual
Neurophysiological level of perception
relationship between an environmental stimulus and a neuron’s firing rate
Perceptual Neuroscience level of perception
relationship between brain activity and a person’s perception
What is the difference between environmental stimulus and attended stimulus?
With humans you know they are attending to a stimulus when the acknowledge it
Does neural firing measure perception?
No. Neural firing will happen without any perceptual information given
Primary visual cortex
responsible for early visual processing (first area in the neocortex that gets information from the eye)
The cell body
where the nucleus, mitochondria, etc. are located
Dendrites
appendages coming off the cell body meant to connect the signals from other neurons
Axon
like an electrical wire that transmits signal from point A to point B within the neuron itselfT
Terminal branches
bind on the dendrites of other neurons so as to communicate the neural signal to other neurons in the neural network
Neural transmission (definition)
a combination of an electrical event which travels down the axon and is followed by a chemical event (neural signal firing)
The electron potential of a neuron
Neurons are often referred to as “integrate-and-fire” meaning they sum their excitatory and inhibitory inputs and if there is a big enough positive number that means the neuron can potentially reach a threshold that will start the firing process
Action potential
the primary method of neural communication
A neuron is limited in its firing rate to only
1000 action potentials a second (usually 400-500)
The synapse
the tiny gap between two neurons, typically between the terminal branches of one and the dendrites of another
When the action potential reaches the end of the axon, it triggers
release of neurotransmitters from the terminal brnaches
Excitatory and inhibitory signals are ___ by the post-synaptic neuron
summed
An excitatory NT will tend to
increase the firing rate of a neuron
An inhibitory NT will tend to
reduce the firing rate of a neuron
We know that firing rate is related to the amount of action potential because
increase in excitatory NTs means lots of action potentials are happening compared to when it is not being released
Single-cell neurophysiology
the experimenter records the activity of a single neuron in response to a stimulus
Process of Single-Cell Neurophysiology
- electrode is inserted into a neuron and the firing rate is recorded
- experimenter notes which types of stimuli make the neuron fire the best (neurons have preferred stimuli)
Examples of tasks to study perception
Recognition/Identification
Visual Search
Detection
Discrimination
Magnitude Estimation
Recognition/Identification Task
there is a relationship between a physical stimulus and your perception of the object (how you categorize it in memory)
higher-level perception
Visual Search task
using a target goal to guide your attention and recognize when the target is found
higher-level perception
Detection task
asked whether or not you can detect a pattern in a field of noise
lower-level perception
Discrimination task
asked to judge the difference between two stimulus (e.g. which of two lines is longer)
lower-level perception
Magnitude Estimation
estimate how much brighter one stimulus is compared to another
lower-level perception
The Weber fraction (k)
measure of discriminative power - the smaller the k, the more sensitive we are to stimulus changes
Fechner’s Law:
S = k log I
Psychophysical scaling
The relationship between physical intensity and psychological magnitutde
Perceptual compression
stimulus intensity increases faster than the perceptual magnitude (i.e. you perceive the stimulus as less intense than it is)
Perceptual expansion
perceptual magnitude increases faster than the stimulus intensity (i.e. you perceive the stimulus as more intense than it actually is)
Detection task question
What is the minimum intensity of a stimulus needed for perception
Absolute Threshold
the minimum amount of energy needed for detection by a perceptual system
Classical Threshold Theory
Predicts a “step” psychometric function - subjects never report detecting the stimulus at intensities below the threshold and always report intensities above the threshold (ideally)
Psychometric function (definition)
relates stimulus intensity to the subject’s detection rate
Typically, the psychomtric function is shaped like
An S – probability of detection gradually increases with intensity and then levels off
Problems with classical threshold theory
relatively minor changes in how the task is worded were found to affect the psychometric function
absolute detection thresholds are influenced by a person’s bias
Signal Detection Theory
uses a mathematical analysis of errors to separate decision factors from perceptual sensitivity
Signal (definition)
activity in the perceptual system related to the stimulus that you are trying to detect
Noise (definition)
activity in the perceptual system that is not correlated with the stimulus/signal (i.e. all that is not the signal)
External noise
originating from outside the perceptual system
Internal noise
originating from inside the perceptual system
Detection improves as you,
increase the signal, decrease the noise, or both
Noise is ___ distributed
normally
Four potentially outcomes of SDT
Hit
Miss
Correct Rejections
False Alarms
Liberal bias
minimizes the misses but generates a lot of false alarms
Conservative bias
minimizes false alarms but generates lots of misses
Bias [does/does not] affect the separation of the noise and signal+noise distributions
does not
Sensitivity (definition)
the ability to differentiate the noise from the signal+noise distributions
When sensitivity is high
the separation between signal and noise is larger and detection is easier
Results of Clark & Clark testing
although both groups had a liberal bias, the Westerners were more likely to respond that stimuli were painful compared to the Nepalese - higher pain thresholds were not due to an actual difference in pain sensitivity
