Introduction to Perception Flashcards

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1
Q

What is the definition of perception?

A

Psychological processes through which we gain knowledge of the world via our senses.

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2
Q

Around how many visual cortical areas do we have?

A

30

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3
Q

Why does perception seem so easy to us?

A

We have so much neural circuitry.

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4
Q

How many photoreceptors do we have in each retina?

A

100 million

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5
Q

How many cells do we have in each cortex of the brain?

A

100 billion

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6
Q

Each nerve cell makes ____ connections to other cells?

A

4000

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7
Q

The oldest branch of experimental psychology is based on the ideas of which two psychologists?

A

Weber (1834) and Fechner (1860)

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8
Q

A central concept of perception is ________ ?

A

Thresholds (limits of perception)

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9
Q

What is a detection threshold?

A

The weakest stimulus needed to evoke a response.

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10
Q

What is a discrimination threshold?

A

The smallest difference between 2 stimuli along a dimension that can be detected.

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11
Q

Measuring detection thresholds: What is the method of limits?

A

Changing the stimulus strength until subject says it is just detectable/undetectable.

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12
Q

Measuring detection thresholds: What is the method of adjustment?

A

When the subject changes the stimulus strength until it is just detectable/undetectable.

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13
Q

Measuring detection thresholds: What is the method of a constant stimulus?

A

When the subject is presented with a constant set of stimulus strengths in a random order and are asked if they can detect it.

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14
Q

What is used to rule out the subject being biased or lying when measuring detection thresholds?

A

Forced choice task.

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15
Q

What happens during a forced choice task?

A
  1. Subject is asked to report something about the stimulus.
  2. In each trial, the stimulus is presented at one of two temporal intervals.
  3. The subject responds either ‘first’ or ‘second’.
  4. The percentage of correct responses is calculated and the threshold.
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16
Q

How is the threshold calculated?

A

The stimulus strength providing 75% correct performance.

17
Q

How do you use a forced choice task to measure discrimination thresholds?

A
  1. Subject is asked to report something about 2 stimuli.
  2. In each trial, the 2 stimuli are presented consecutively.
  3. The subject responds which has the greatest strength.
  4. The percentage of correct responses is calculated and the threshold.
18
Q

Who came up with Signal Detection Theory?

A

Green & Swets (1966)

19
Q

What is Signal Detection Theory?

A

Sensory systems are noisy and imperfect.
Sometimes internal noise interferes with perceptual decisions about the world when the stimulus is weak.
This can lead to incorrect decisions sometimes.
Thresholds are probabilistic, not absolute measures of performance.

20
Q

Why is the transition from chance to perfect performance gradual?

A

This can be explained by Signal Detection Theory.

21
Q

What is single cell recording? (neurophysical approach)

A

Recording electrical activity of cells in sensory pathways.

22
Q

What happens during single cell recording?

A
  1. Extracellular recordings in visual/sensory areas are taken
  2. Action potentials are measured to determine a cell’s preferered stimulus
  3. Microelectrode is surgically placed into the area, slowly positioned next to the axon
  4. Electrical signals are amplified and sent to a speaker
  5. Experimenter maps receptive field of the cell
23
Q

What does PSTH stand for and what is it?

A

Peri stimulus time histogram. This is a plot showing how the firing rate of a cell changes during the time a stimulus is presented. (usually measures in AP/s)

24
Q

Why is neurophysiology reductionist? Why is this a problem?

A

Single cell recording attempts to reduce a complex problem into something that can be easily measured.
This is a problem because it tells us little about perceptual process which may rely on the combined activity of many neurones.

25
Q

Why can’t individual cells be considered as feature detectors?

A

This is because the activity of ANY cell is ambiguous with regard to the actual stimulus that made it respond.

26
Q

What are 2 limitations of PET scans?

A
  1. Requires radioactive tagging
  2. Has poor spatial accuracy
27
Q

What is a strength and limitation of fMRI scans?

A

Strength: Good spatial accuracy
Limitation: The link between fMRI and activity is not clear

28
Q

What are 2 strengths and limitation of both EEG and MEG scans?

A

Strengths: Fast & measures electrical activity across the brain

Limitation: Poor spatial accuracy