Illusions and experiments of consciousness Flashcards
Necker cube
Three-dimensional cube that can be perceive in two different angles but not simultaneously - shows that conscious perception is serial
Ebbinghaus illusion
Perceptually different, physically identical circles
- perception suffers from illusions - participants reported wrong size (same or not?)
- action not influenced by illusions - participants accurately gripped according to stimuli presented
Dorsal and ventral visual streams
Dorsal stream - focused on location of object and actions based on such
Ventral stream - focused on perception and recognition of objects
Troxler fading illusion
When staring into one part of an image, the rest of the background will seemingly disappear
Monkeys and neuronal correlates of conscious experience
Primary visual cortex fired depending on objective perception.
Higher visual areas such as V4 and inferotemporal cortex fired more strongly when preferred image
DF - match and post experiment
DF was unable to match the orientation of a card given, but could successfully slot it in through a gap, showing that actions are not always linked to conscious perception
fMRI on subliminal priming
- ventral visual cortex could be activated unconsciously
- fusiform gyrus can be activated unconsciously, with shape recognition and reading mechanisms
McGurk effect
Visual stimulus suggests “ga ga ga”, auditory stimulus suggests “ba ba ba”, conflict resolved by producing “da da da”
Subliminal priming
Marcel - shows subliminal word, participants picked colour quicker than when shown irrelevant words
Greenwald - priming effect shown to be based on letter combinations rather than meaning
Dehaene - priming effect shown using numbers
Dehaene (2001) - repetition priming
Experiment 1:
Two conditions: visible (followed by blank) and invisible (preceded by blank) mask
7% of masks were recognised but only one word was ever identified
Experiment 2 (to assess specificity):
Mask matches in terms of case x word (or neither), then semantic classification (manmade or natural)
Case-independent repetition suppression in left fusiform gyrus
Case-dependent repetition priming in right extrastriate regions
Dehaene (2001) - ERPs in experiment 1
In invisible condition:
P1 was weaker and delayed
N1 only in left anterior temporal area
N400 was absent
P3 was absent
All of these ERPs were present in visible conditions
Facial recognition in monkeys
Facial recognition cells found to only activate when looking at faces and not patterns
Subliminal semantic processing
Is the target number smaller (left hand) or larger (right hand) than 5 or five?
Two conditions: unmasked, masked
Target shown in either words or numerals
Reaction time was smaller for Arabic numerals
Reaction time was larger for incongruent masks
Higher contralateral motor cortex activity found for overt hand responses
Unconscious sounds
Objective task: detect sound, then identify sound
Disadvantages: blindsight, lack of motivation, stimulus strength
Consciousness decided based on task performance
Subjective task: did you feel a stimulus?
Disadvantages: criterion issues (liberal / conservative)
Consciousness decided post-hoc
Aperture problem
Direction of motion and movement can be ambiguous when looking through a hole
Go / no-go
2x2 design: (un)conscious x (no-)go (square is go, diamond is no-go)
- unconscious no-go signals still elicited go responses but delayed (signal processed for inhibition but not sufficient)
- prefrontal cortex activation found in unconscious condition
Positives: unconscious stimulus highly task-specific and associated with prefrontal cognitive control
Attentional blink experiment
Does meditation reduce attentional blink?
Hypothesis 1: attention will be captured less by T1 leading to less attentional blink for T2
- higher T2 detection after long interval
- improved T2 detection did not affect T1
- T2 detection improved over time
Hypothesis 2: smaller T1-elicited P3b (shows resource allocation)
- significant T1 P3b reduction in practitioners
- T1 P3b reduction correlated with attentional blink reduction
Is reduction in T1 focus related to a second stimulus T2?
Yes, this T1 reduction only occurs when T2 is present.
No reduction in T1 focus was found when T2 was either delayed or not shown at all.
Possible confounds in attentional blink experiment
- Hawthorne effect - alteration of behaviour when observed
- placebo effect
- participants not blind to conditions
- trait effects (no follow-up)
- not matched on nutrition or sleep
Maguire et al. (2000) - cab drivers
London cab drivers have larger posterior hippocampi related to cognitive and spatial processing
Focused attention vs open monitoring meditation on attentional blink
Hypothesis: smaller attentional blink during open monitoring compared to focused attention
Result: only experienced meditators showed smaller attentional blink during open monitoring compared to focused attention (they can control cognitive functions)
