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Chapter 4: Sensation & Perception
• Sensation and perception• Attention
Announcement
Quiz 1 , this Sunday, 11:59pm Writing Assignment 1, this Thursday,
11:59pm
***1. Identify the basic principles that apply to all the senses. (transduction, receptors, thresholds, doctrine of specific nerve energies)
***2. Track how our minds build up perceptions. (primary-sensory-association cortex, top-down vs. bottom-up, figure-ground, parallel processing)
3. Analyze the scientific support for and against ESP. ***4. Explain how the eye starts the visual process. **5. Identify the different kinds of visual perception (shape, color,
motion) **6. Describe different visual problems (blindness, colorblindness,
blindsight) ***7. Explain how the ear starts the auditory process. ***8. Identify the different kinds of auditory perception **9. Identify how we sense and perceive odors and tastes. **10. Describe the three different body senses (touch, body
position, balance) 11. Describe the field of psychology called human factors.
Sensation Senses gather information about the
world by detecting energyThen send that info to the brain
Sensation is the detection of physical energy by our sense organs
Perception
The brain’s interpretation of raw sensory data
Sensation allows us to pick up signals from our environment,
Perception allows us to assemble the signals into something meaningful
Sensation and Perception Are they the same?
No!
Sensation The detection of physical energy by our sense organs which then goes to the brain
Perception the brain’s interpretation of raw sensory date
Brain uses only a subset of sensory information and fills in the rest
Illusions happen when these two don’t match up
When Senses Meet the Brain
After being transduced, our brains then organize the sensory data into meaningful concepts
Our brains piece together A) What’s in our sensory fieldB) What was there a moment agoC) What we remember from our past
Processing in the brain
Parallel processing
The ability for the brain to process multiple
sensory attributes at once
Receive information across different neural
pathways simultaneously
The Multitasking Brain
Bottom-Up Processing: sensory information comes to the brain and the brain pieces it togetherConstructing a whole from the parts
The Multitasking Brain
Top-Down Processing: make sense of things using our experience and background knowledgeUnderstand general meaning by context
Demonstration
Right side – close eyes Left side – open eyes
Demonstration
Right side – open eyes
Left side – close eyes
What Are We Looking At?
A woman A duck A trained seal A man’s face A mountaintop
Reveal
Top-Down Processing
The Multitasking Brain
Top-Down Processing: recognition depends on higher-level cognition such as expectations
Perceptual Set: a readiness or predisposition to perceive a stimulus in a certain way
Steps in the Sensation Process
Accessory Structure: Collect energy from worldSense receptor: Turns energy into neural activity (Transduction)
Sensation Transduction: The process of converting
external energy into neural activityAllows the brain to understand that energyAlmost like the information is being translated
Sense Receptors are specialized cells that convert the energy to neural activityDifferent for each sensory system
Steps in the Sensation Process
Accessory Structure: Collect energy from world
Sense receptor: Turns energy into neural activity (Transduction)
Sensory Neurons Thalamus Cerebral Cortex (Perception)
Sensation
Sensory Adaptation: process where we respond strongly to a stimulus at first, but then get used to it after timeOur receptors begin to respond less to save
energyE.g., sitting on a chairWhat would be the evolutionary explanation
for this?
Doctrine of Specific Nerve Energies
The sensation we experience is determined by the sense receptor, not the stimulusSense receptors = cells in our eyes, ears,
fingertips,etcStimulus = light, sound, touch, etc
Measuring Sensation
Psychophysics: the study of how we perceive stimuli based on their physical characteristics
Absolute Threshold Lowest level of a stimulus needed for the nervous system to
detect it 50% of the time
Just Noticeable Difference (JND) The smallest change in the intensity
of a stimulus that we can detect 50% of the time
Weber’s law Constant proportional relationship
between the JND and original stimulus
Weber’s law WHEN you can detect a change
Signal Detection Theory Signal Detection Theory: describes how we
detect stimuli under uncertain conditions
Response Bias: how likely someone is to make one type of guess over another when they’re in doubt.
Signal-Detection Theory
True Positive (Hit)
False Negative (Miss)
False Positive / (False Alarm)
True Negative (Correct Rejection)
Respond “NO”
Stimulus Present
Stimulus Absent
One’s Decision:
Ringing of the phone
Respond “YES”
True Positive (Hit)
True Negative (Correct Rejection)
Signal Detection Theory Theory regarding how stimuli are detected
under different conditions Signal-to-noise ratio
Basically how difficult is it to detect a signal under uncertain conditions
Different situations require a different “response bias”
I-ClickerParticipants in a study are watching a computer screen, which displays randomly appearing dots of different colors. Each time participants see a red light they press “enter.” When participants are told they will lose $1 every time they incorrectly indicate they have seen a red light, their number of __________ will increase.
A. True Negatives
B. False Negatives
C. True Positives
D. False Positives
Signal-Detection Theory
True Positive (Hit)
False Negative (Miss)
False Positive / (False Alarm)
True Negative (Correct Rejection)
Respond “NO”
Stimulus Present
Stimulus Absent
One’s Decision:
Ringing of the phone
Respond “YES”
I-ClickerPierre is a new father who worries that he will be unable to hear his infant daughter cry at night. He often thinks that he hears her crying and runs to her bedroom only to find that she is sleeping soundly. However, when she really does cry at night, Pierre always hears her and runs to pick her up. According to signal detection theory, Pierre’s _____________ is very low, which results in many _____________A. Response Bias ; False Positives (False Alarms)B. Response Bias ; False Negatives (Misses)C. Sensitivity ; True Positives (Hits)D. Sensitivity ; True Negatives (Correct Rejections)
Signal-Detection Theory
True Positive (Hit)
False Negative (Miss)
False Positive / (False Alarm)
True Negative (Correct Rejection)
Respond “NO”
Stimulus Present
Stimulus Absent
One’s Decision:
Ringing of the phone
Respond “YES”
I-ClickerParticipants in a study are watching a computer screen, which displays randomly appearing dots of different colors. Each time participants see a red light they press “enter.” When participants are told they will be given $1 every time they correctly indicate they have seen a red light, their number of __________ will increase.
A. True Negatives
B. False Negatives
C. True Positives
D. False Positives
Signal-Detection Theory
True Positive (Hit)
False Negative (Miss)
False Positive / (False Alarm)
True Negative (Correct Rejection)
Respond “NO”
Stimulus Present
Stimulus Absent
One’s Decision:
Ringing of the phone
Respond “YES”
Attention
Selective Attention: process of focusing on a specific aspect of experience while ignoring others
Cocktail Party Effect
Directing Attention Inattentional Blindness: when your
attention is focused on something, other stimuli in the environment may be ignored
Change blindness: a failure to detect obvious changes in one’s environment
Video1: http://www.dansimons.com/videos.html Video 2:http://www.youtube.com/watch?v=voAntzB7EwE
Subliminal
Subliminal perception: the processing of sensory information that occurs below the conscious awareness
Subliminal persuasion: subthreshold influences over decision making