PSYCH 104 Midterm 2 (sensation and perception) Flashcards
Sensation
- Sensation
○ The process by which (objective) stimuli are detected, transduced into nerve impulses and sent to the brain
Perception
- Perception
○ The brains interpretation of raw sensory inputs
Transduction
- Transduction
○ The process of converting an external energy or substance into electrical activity within neurons
Sense receptor
- Sense receptor
○ Specialized cell responsible for converting external stimuli into neural activity for a specific sensory system
Sensory adaptation
- Sensory adaptation
○ Activation is greatest when a stimulus is first detected and then declines in responsiveness
○ Also called neural adaptation
Psychophysics
- Psychophysics
○ The study of how we precieved sensory stimuli based on their physical characteristics
Absolute threshold
- Absolute threshold
§ Lowest level of a stimulus needed for the nervous system to detect a change 50 percent of the time
○ Just noticeable difference (JND)
§ The smallest change in the intensity of s stimulus we can detect
○ Weber’s law
§ There is a constant proportional relationship between the JND and original stimulus intensity
§ I = intensity of the stimulus
§ K = constant
JND
JND: the louder the volume is, the greater the change in volume that is needed to detect a difference
JND (Formula)
JND = K x I
§ I = intensity of the stimulus
§ K = constant (0.10)
Signal detection theory
Signal detection theory
- Asks two questions
○ Was waldo in the image?
○ Did you say waldo was in the image?
Signal
Signal = stimulus to be perceived
Signal detection theory (Noise)
Noise = everything else
What does Increased sensitivity to the signal cause?
Increased sensitivity to the signal causes hits and correct rejections to occur more often
What does Decreased sensitivity to the signal cause?
Decreased sensitivity to the signal causes misses and false alarms to occur more often
How are differences in sensitivity measured?
Differences in sensitivity are measured with a statistic called D-prime
- A measure of the stimulus salience
- Plotted using ROC curves (Receiver operating characteristic curves)
What does a perfect signal detection theory test do?
A perfect test hugs the Y axis
- You want the curve to bend as close to the top left curve as possible
Police line ups accuracy?
Police lineups accuracy
- One by one: 30% accurate
- All at once: 39% accurate
- The false alarm rate is higher in the all at once
What do police line ups show us?
This shows us that the simultaneous method is better than the sequential but it is barely noticeable
What do polygraphs need to be accurate?
Polygraphs: they actually need to be set in terms off sensitivity un order to administer the test
What is the issue with polygraphs?
They are more correct than not but they also make many false positives
Perception
Perception
- Perception is determined by three basic elements
○ What is currently being sensed
○ What was sensed
○ What has happened in the past
Perception - Parallel processing
- Parallel processing: the ability to attend to many sense modalities simultaneously
Perception - Bottom up processing:
- Bottom up processing: processing in which a whole is constructed from its parts
Perception - Top-down processing
- Top-down processing: conceptually driven processing influenced by beliefs and prior learning
Perceptual set
Perceptual set: A set formed when expectations influence perceptions
Perceptual constancy
Perceptual constancy: the process by which we perceive stimuli consistently across varied conditions
What is the disclaimer about perceptual sets?
A disclaimer: perceptual sets and constancy are just concepts which describe patterns of behavior in relation to sets of stimuli
- They do not provide an explanation of that pattern of behavior
Attention - Selective attention
- Selective attention
○ The process of selecting one sensory channel and ignoring or minimizing others
§ Assumed to be controlled by the reticular activating system (RAS) and higher cortical regions
Attention - Filter “theory” of attention
- Filter “theory” of attention
○ Attention is a ‘bottle neck’ through which information passes
§ Dichotic listening: a research design in which subjects have a message delivered to each ear independently through headphones. Both messages are delivered simultaneously, but only the attended ears message is able to be accurately recalled
Inattentional blindness
Inattentional blindness
- Failure to detect stimuli that are in plain sight when our attention is focused elsewhere
Change blindness
- Change blindness
○ Failure to detect changes in a visual stimulus
Subliminal messaging
Subliminal messaging: putting messages into music or other broadcasts that we observe and interpret unconsciously
- It can also be noted that it does not work and that has been proven numerous times over
Extrasensory perception (What is it?)
Extrasensory perception
- Perception of events outside the known channels of sensation
Extrasensory perception - Precognition
○ Precognition
§ Predicting events before they occur though paranormal means
□ Eg. What cards will appear
Extrasensory perception - Telepathy
○ Telepathy
§ Reading others minds
Extrasensory perception - Clairvoyance
○ Clairvoyance
§ Detecting the presence of objects that are hidden from view
Zener cards
Zener cards: used to test precognition, telepathy, and clairvoyance
- Used by Rhine
Zenner cards results of the Rhine tests?
<– the results of the tests
○ They were higher than expected
How large must a group of people be before the probability of two people sharing the same birthday exceeds 50%?
§ A: 23
