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