Psyc PPT V2

8/3/2019 Psyc PPT V2

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Is Unconscious Movement Initiation an Artifact of the Clock?

Presenters: Pollyna. Shirley. Soon Hyung. Wai Chit. Wiharjo


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Electroencephalographic

What does this long word mean???

What is eeg?electroencephalographic

The recording of electrical activity alongthe scalp produced by the firing ofneurons within the brain

Recording of brains spontaneous

electrical activity Over a short period of time Recorded from multiple electrodes
http://upload.wikimedia.org/wikipedia/commons/7/7e/1st-eeg.png


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WHO? Libet, Gleason, Wright, and Pearl

(1983)

WHAT? Recorded the electroencephalographic

(EEG) activity of people instructed togenerate occasional spontaneoushand movements.

HOW? Report the time of each spontaneous

decision to move by identifying thelocation at that time of a spottraveling around a clock display.

Brain Activity &consciousness


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RESULTS: Readiness potential (RP)

Began approximately 350 ms before the times at which people indicatedthey had decided to move

This pattern has been replicated several times

(e.g., Haggard & Eimer, 1999; Trevena & Miller, 2002).

SO? Results suggest that spontaneous decisions to move are initiated by the brain

before people are consciously aware of having made these decisions

Brain Activity &consciousness


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Negative-going shift in the EEG recorded atthe Cz electrode.

Logically impossible for negative shift toarise only in conjunction with movement

preparation.

Possibility of other brain processes?

Then its appearance before the consciousdecision to move DOES NOT truly support

the claim that movement preparationbegins unconsciously.

How reliableis the study?


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2 Experiments Jeff Miller, Peter Shepherdson and Judy Trevena

Negative shift is caused primarily (possibly exclusively)

The requirements to monitor the clock display

To report the spots position at the moment of thespontaneous decision to move.

Both time-monitoring processes + Movementpreparation

Possibility of inference ?

What should wedo then?


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IV: Time Monitoring

DV: negative shifts in EEG waves

Hypothesis: EEG waves are aresult of clock monitoring, not themaking of conscious decisions tomove.

Experiment 1


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Who were involved?

Participants

12 participants

- 8 Males, 4 Females

Students of University of Otago

Aged 19 30 (M=23.7)

Each session lasting 2.5 hr


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Responses recorded by IBMcomputer

Key-press responses made with

index finger of right hand on the Ikey

A spot indicated by a white crossmoved clockwise at constant 2.5sper circuit

Apparatus


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8 blocks of 20 trials (10 with clock, 10 w/o clock) Order of trials randomized In trials with clock, spot will move around the

clock perimeter starting from the top center Participants were told to relax, and generate

spontaneous key press. Told not to preplan but emit on an abrupt basis The moving spot will stop 500-800ms after the

key press response, after which the participantuse the left/right arrow key to reposition spot.

Procedures


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What are the findings?

Pre-movement negativity in EEGmay have resulted frommonitoring the clock rather than

from unconscious preparation formovement

EEG activity at start of trial wasalso affected by the clock,probably due to obvious visual

stimulation bet. clock andwithout clock

Miller J et al. Psychological Science 2010;22:103-109


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Who were involved?

Participants

12 right-handed volunteers

Aged 19 30

Did not do experiment 1


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Tones not obviouslyof different pitches

Volume forconversationalspeech

Experiment 2


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Accuracy > speech

Only informed whichkey to press aftersound was made

Experiment 2


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Presence of the clock had a significant impact on the EEG activity

Presence of a moderating variable



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Miller J et al. Psychological Science 2010;22:103-109


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Greater fluctuations in Cz amplitude with the presence of a clock

Clock monitoring affects the level of EEG activity

Rejects the hypothesis suggested in the previous study

Presence of the clock


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There was less EEG activity than there was in Experiment 1

Less brain activity required to listen out for tone(compared to choosing to move)

EEG activity from clock monitoring + EEG activity from task= Total EEG activity

Moderating variable:

The type of task


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Background Research

(Haggard & Eimer; Libet et al; Trevena & Miller)

Influence of the clock?


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Current Research

Challenge to the previous research

Experiment 1 Key-press movement

Negativity may result from monitoring clock

Experiment 2 tone for pitch judgment task

Moderating effect of the task


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Heisenberg Uncertainty Principle

The measurement process interferes with the

processes to be measured

Need more experiments

Psyc PPT V2

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