Chapter 1: Sensation and Perception Flashcards

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1
Q

What’s the major difference between sensation and perception?

A
  • Sensation - stimulation of the sensory organs (ex. touching a fuzzy surface)
  • Perception - Organizing sensory information into representations of the physical stimulus (ex. registering the fuzzy surface as a blanket).
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2
Q

What’s one thing to note about sensation and perception?

A
  • Perception comes after sensation
  • This makes sense since perception gives meaning to all the sensory signals we receive. It also occurs automatically
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3
Q

What’s an important step that occurs between sensation and perception?

A
  • Transduction. Turns sensory stimuli into neural signals that can be sent to and interpreted in the brain.
  • Turns physical dimensions into perceptual dimensions (ex. wavelength into colour)
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4
Q

What are the two types of environmental stimuli and their respective definitions?

A
  • Distal - The thing in the world seen at a distance (ex. a tree)
  • Proximal - The physical phenomenon that impinges on sensory receptor cells (the light waves reflecting off the tree and into your eyes)
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5
Q

What is the Principle of Neural Representation?

A
  • All that we perceive is not based on direct contact with stimuli but on representations (neural codes) in the receptors and brain
  • Same occurs when visualization in the mind is happening
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6
Q

What happens after a signal from a stimulus is transduced to the brain?

A
  • They go to their respective primary receiving area in the brain.
  • Each sense has its own general area, differing in size
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7
Q

What’s the difference between a primary processing centre and association areas?

A
  • Primary processing centres is where the signal first travels to when it arrives in the brain
  • Association areas are where the brain attempts to coordinate and organize the different senses in order to perceive the surroundings.
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8
Q

Why is neural processing so important?

A
  • Required to form an integrated conscious experience, store it in memory etc.
    *Some info may be sensed, but not attended to.
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9
Q

What are the two types of neural processing?

A
  • Bottom-up processing - processing based on the stimuli reaching the receptors (ex. getting a paper cut)
  • Top-down processing - an observers knowledge, expectations, and goals, all of which can affect perception (ex. reading)
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10
Q

Who is the scientist responsible for developing the field of psychophysics?

A
  • Gustav Fechner (early to late 19th century)
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11
Q

What were the three ways that Fechner devised to empirically evaluate the mind?

A

1) Absolute threshold
2) Difference threshold
3) Magnitude estimation (correspondence between physical and perceptual magnitudes)

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12
Q

What was the initial definition of absolute threshold?

A
  • The minimum stimulus intensity that can just be detected by the brain
  • Meant to represent the boundary between sensing and not.
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13
Q

What were the three classical methods used for determining the absolute threshold for an individual?

A
  • Method of limits
  • Method of adjustment
  • Method of constant stimuli
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14
Q

What’s the method of limits?

A
  • A reasonably quick and fairly accurate way of classically measuring the absolute threshold.
  • Experimenter presents a stimulus of a given intensity and continuously asks participants if they can detect the stimulus. They will increase or decrease the stimulus depending on their response.
  • Boundary value is taken and process is repeated but this time started in the other direction
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15
Q

What’s the method of adjustment?

A
  • A quick and dirty, classical estimate of the absolute threshold
  • Start at a given stimulus intensity and the participant is able to increase or decrease the intensity of the stimulus until they identify the threshold level.
  • Not as precise as the participant may overshoot the boundary since they may not be that sensitive
  • The process is repeated, and the average is taken
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16
Q

What’s the method of constant stimuli?

A
  • The most time-consuming but most accurate classical method in determining the absolute threshold
  • 5-9 selected stimuli of ‘constant’ intensities are repeatedly presented in a random order. These results are then graphed as a probability of detection
17
Q

What new definition of the absolute threshold was derived from the method of constant stimuli?

A
  • Absolute threshold - lowest intensity necessary for a stimulus to be detected 50% of the time.
18
Q

What does it mean to have a lower threshold?

A
  • Means you are more sensitive to lower levels of stimulus
19
Q

How does adaptive testing work?

A
  • Builds off the method of limits but is much more efficient
  • each time a response changes, the direction of the stimulus also changes (also called the staircase method)
  • End up hovering/oscillating over a specific value, that being your threshold
  • Everything depends upon the participant’s response
20
Q

What’s the difference threshold?

A
  • Also called the just-noticeable difference (JND)
  • The smallest difference between two stimuli that people can detect (50% of the time)
  • The minimum difference between 2 stimuli before you can tell they are different
21
Q

How is the difference threshold/JND measured/determined?

A
  • Using Weber’s law which states that the size of the JND is proportional to the magnitude of the first stimulus
  • Each type of stimulus has its own constant fraction that’s used
  • As stimulus get more intense, the difference must also increase for us to be able to perceive it (or constant difference get less and less noticeable)
22
Q

What does psychophysical scaling involve?

A
  • An attempt to discern whether perception matches/corresponds to the changes in sensation/environmental changes.
  • Varies for each sense
23
Q

What’s response compression vs. response expansion?

A
  • Terms used in psychophysical scaling.
  • Response compression - don’t perceive gradual increases in stimulus as to what the environment reflects (this is the case with brightness)
  • Response expansion - Perceive the change in sensation much greater than it actually was (this is the case when experiencing pain)
24
Q

What does Steven’s Power law describe?

A
  • The relationship between physical and perceived intensity follows the same equation across all values of a stimulus type
  • P = KS^n (the constant is not super relevant)
25
Q

What’s the purpose of the Signal Detection Theory?

A
  • Want to differentiate people’s perception to a change in stimulus as valid or not (are they actually super-sensitive or just less conservative?)
  • A decision criterion is set to ensure the person is actually detecting the stimulus or not
  • Sometimes the stimulus will change, sometimes it won’t. These are often referred to as catch trials.
26
Q

What are other influences on threshold?

A
  • Personality
  • Level of fatigue/attention (too tired can cause you to miss the stimulus)
    -Rewards/cost
  • Noise that interferes with the individual’s ability to catch the stimulus
27
Q

True or false: There is a fixed level of sensitivity.

A
  • FALSE
  • Perception depends on sensation and cognitive processes (as indicated by the signal detection theory)
  • There’s no fixed level of sensitivity