Chapter 2- Perception Part 2 (In sight but out of mind to end)

Question 1

What is inattentional blindness?

Answer 1

Failure to perceive the appearance of an unexpected object. –> failure to detect PRESENCE.

Recall: gorilla video –> they play during GEQ class –> what were u doing during geq class lel obviously not paying attention.

Question 2

What is change blindness?

Answer 2

Failure to detect that a visual stimulus has moved, changed or has been replaced by another stimulus.

Failure to detect MOVEMENT.

Question 3

What is change blindness blindness?

Answer 3

Being too optimistic about how you are able to detect visual changes and so avoid change blindness.

We actually do this a lot.

Question 4

When do you expect change blindness to occur?

Answer 4

1) Marginal interest vs Central interest.
- Like what is in the background vs what is in the centre. Latter is less susceptible to change blindness.

2) Incidental approach vs intentional approach
- Not being told beforehand to expect a change vs being told beforehand
- Latter is less susceptible to change blindness.

Question 5

Is it true that if one is told beforehand to look out for changes, he or she will not be susceptible to change blindness? Why?

Answer 5

No. Our long-term memory for complex scenes can be much less impressive than we believe to be the case.

• Asking students to identify what is wrong with a picture of a familiar scene on their college campus.
• Nearly all rated the scene as familiar but only 20% detected the change.

Question 6

Distinguish between type change and token change, both of which play a role in attention in change blindness.

Answer 6

Type change: In which an object was replaced by an object from a different category

Token change: in which an object was replaced by an object from the same category

Question 7

What were the findings associated with type and token change?

Answer 7

1) Changes were much more likely to be detected when the changed object had received attention before the change occurred.
2) Change detection was much better if it’s a type change as compared to a token change.

Question 8

What is change blindness caused by?

Answer 8

An inability to retain detailed information about a visual scene beyond a brief period and attentional lapses.

Question 9

When you say that you show change blindness because you are not paying attention to that object, what are you assuming?

Answer 9

Assuming that our visual perception of unattended objects is very incomplete.

Question 10

What can be done to debunk this assumption?

Answer 10

Show that we initially form detailed and complete representations but these representations decay rapidly or are overwritten by a subsequent stimulus. Would be consistent with our subjective impression that we briefly have access to reasonably complete information about the visual scene in front of us.

Observers were presented with an array of 8 rectangles (some horizontal and some vertical), followed later by a 2nd array of 8 rectangles 1600ms later. Observers’ task was to decide if any of the rectangles had changed orientation from horizontal to vertical and vice versa.

There was very little change blindness provided the observers’ attention was directed to the rectangle that might change within 900ms of the offset of the first array. Thus, we have access to fairly complete information about a visual scene for almost 1s provided no other visual stimulus is presented.

Question 11

What is sublimal perception?

Answer 11

Perceptual processing occurring below the level of conscious awareness that can nevertheless influence behaviour.

Question 12

How do we decide if an observer is consciously aware of a given visual stimulus?

Answer 12

Subjective threshold: This is defined by an individual’s failure to report conscious awareness of a stimulus. Most obvious but not the best measure to use.

Objective threshold: An individual’s ability to make an accurate forced-choice decision about a stimulus (guess at above-chance level whether something is a word or not)

Question 13

Why is using the objective threshold a better method?

Answer 13

Does not rely on possibly inaccurate or biased reports of their conscious experience.

Question 14

What did the experiment on masked priming and sexual stimuli show?

Answer 14

Straight people attracted to N00DS of opposite sex.
Gay men attracted to gay men, lesbian in between.

Shows perceptual processing of invisible sexual stimuli.

Question 15

What is blindsight?

Answer 15

An apparently paradoxical condition often produced by brain damage to the early visual cortex, in which there is behavioural evidence of visual perception in the absence of conscious awareness.

something like can feel cannot see (something like love LEL love is blind)

Question 16

Which part is damaged in blindsight patients?

Answer 16

Early visual cortex.

Question 17

How did GY differ from healthy individuals when asked to report the part of the visual field to which the stimulus had been presented, and when told to report the opposite of the stimulus’ actual location?

Answer 17

GY was presented with a stimulus in the upper or lower part of his visual field.

• Tended to respond with the real rather than the opposite location on exclusion trials as well as inclusion trials. -> suggests that he has access to location information but lacked any conscious awareness of that information.
• Healthy individuals showed a large difference in performance on both inclusion and exclusion trials –> suggests they had conscious awareness.

Question 18

Explain how DB experienced blindsight.

Answer 18

Showed some perceptual skills including the ability to detect whether something has been presented to the blind side of his visual field, and being able to identify its location. However, he reported no conscious experience in his blind field.

Question 19

What is AFFECTIVE blindsight?

Answer 19

The ability to discriminate among different emotional stimuli in spite of the absence of conscious perception.

Question 20

What problem do you prevent if you use a scale to judge perceptual awareness?

Answer 20

Use of a sensitive method to assess conscious awareness suggests that degraded conscious vision sometimes underlies blindsight patients’ ability to perform at above-chance levels on visual tasks.

Question 21

What are the 2 types of blindsight?

Answer 21

Type 1: no conscious awareness
Type 2: have conscious awareness that something is present, but cannot see it.

Does blindsight exist on a continuum?

Question 22

What is categorical perception?

Answer 22

The finding that when a sound is intermediate between the 2 phonemes, the listener typically perceives one or other of the phonemes.

Question 23

Illustrate how categorical perception can be influenced by amplification effect.

1) Phoneme
2) Nonspeech sounds

Answer 23

1) Phoneme and the amplification effect
- When two auditory stimuli of opposite sides of the boundary (eg. /ba/ vs /da/) were presented at the same time, differences in brain activation of the 2 stimuli were strongly amplified.

2) Music.
Musicians showed much clearer evidence of categorical perception than nonmusicians when categorizing chords as A minor or A major.
Since musicians have stronger categorical perception for chords, it shows the role of exposure and practice. Categorical perception phonemes is so strong possibly because we are all expert listeners to phonemes.
This suggests that categorical perception also occurs with nonspeech sounds. Hence speech processing did not involve a special mechanism but a general mechanism for sounds.

Question 24

Is categorical perception a top-down process?

Answer 24

Yes.

Question 25

How can categorical perception be influenced by context?

Answer 25

eg: lets you hear a word that sounds either like dash or tash.
- Context effect: An ambiguous initial phoneme was more likely to be assigned to a given phoneme category when it produced a word than when it did not.

Question 26

Does speech production affect speech perception? How to prove this?

Answer 26

Yes

Applied TMS to the motor cortex to inhibit processes associated with lip movements. Led to impaired categorical perception of speech sounds involving lips in their articulation.

Question 27

What are some of the problems one might potentially face in speech perception?

Answer 27

1) spoken language is very rapid, at about 10 phonemes/second.
2) segmentation problem: difficult to find out where a word ends and where a word starts.
3) coarticulation problem: sounds of phonemes are not invariant. changes depending on the word it is paired with. Eg: bull, bell, bill
4) listeners in everyday life often try to understand degraded speech.
5) individual differences among speakers.

Question 28

How do you mitigate the segmentation problem?

Answer 28

1) Know that some phonemes don’t occur together in the language you speak.
Eg: /m/ and /r/ are never found together in english words.

2) Possible-word constraints.
- Eg knowing that a stretch of speech lacking a vowel isn’t a possible word
- Eg: cannot tell the vowel /a/ in ‘fapple’ because it’s unlikely to be a word, but can do so in ‘vuffapple’ because ‘vuff’ could conceivably be an English word.

3) stress:
- in english, the initial syllable of most nouns and verbs is stressed

Question 29

What is the McGurk effect?

Answer 29

When there is a conflict between a spoken phoneme and a speaker’s lip movements, the sound that is heard combines auditory and visual information.

Question 30

Is the McGurk effect processed by bottom-up processes?

Answer 30

No. By top-down.

Most listeners show the McGurk effect when the crucial word (based on blending the discrepant visual and auditory cues) is consistent with the meaning of the rest of the sentence than when it was not.

So in a way it’s top-down because you look at the sentence’s meaning first (top) before you zoom in to the word and decide what it is.

Question 31

McGurk prepared a videotape of someone saying “ba” repeatedly. The sound channel then changed and so there was a voice saying “ga” in synchronization with lip movements saying “ba”. Listeners heard “da” instead.

What does this illustrate about the McGurk effect?

Answer 31

Provides compelling evidence that speech perception involves a blending of visual and auditory information.
Robust, works for voices of both sexes.

Question 32

What is the phonemic restoration effect?

Answer 32

The finding that listeners presented with a sentence including a missing phoneme use the sentence context to identify it and are not aware that it is missing.

Question 33

Why are we not aware of the missing phoneme?

Answer 33

Reliance on contextual information meant that this is a top-down process, and it is used to create expectations about what we are likely to hear

Question 34

What did the use of ERPs suggest about the timing context influences speech perception?

Answer 34

Contrary to the traditional view, contextual information has a rapid influence on speech perception, and is actually not processed after information concerning the meanings of words within a sentence.

Question 35

What does the motor theory propose about speech perception?

Answer 35

Assumption that listeners effectively mimic the articulatory movements of the speaker.
The motor signal produced hence provides much less variable or inconsistent information about what the speaker is saying.
Hence motor system can be used to assist speech perception

Question 36

What occurred when participants underwent TMS?

Answer 36

Motor theory predicts that listeners would find it harder to perceive speech if parts of the motor system were disrupted by rTMS.
Applying rTMS to left premotor cortex impaired performance on a listening task requiring language processes.