Lecture 2: Psychophysiological Measures Flashcards
Psychophysiology
The study of the natural (i.e. physical) basis of the mind
The branch of psychology that studies the relationship between ‘mind’ and ‘body’
Supplements standard psychological measurements (behavioural) with physiological measurements
Types of physiological measure
Physiological measures objectively record the real, automatic responses elicited in our body to psychological stimuli
Central Nervous System (brain & spinal cord)
effects on cognition and affect
hormonal responses
Peripheral Nervous system (nerves)
Somatic Nervous System
effects on movement
Autonomic Nervous System
effects associated with the “fight or flight” mechanisms
changes associated with fear, anxiety, arousal
Enteric Nervous System
effects on digestion
So why use them?
Physiological measures are: objective quantifiable hard to fake immune to response bias often unconscious
Autonomic measures
(Look at Powerpoint)
Autonomic reactions
Autonomic Arousal
orienting responses
changes in alertness, arousal, or attention
fight or flight reaction
a response to fear
readying the body for action via adrenaline, leading to increased heart rate, blood to muscles, breathing, etc.
Autonomic responses are not emotion-specific
Galvanic Skin Response (GSA, or electro-dermal activity (EDA)
Measures changes in the electrical resistance of the skin (or conductance: Biopacs use micro siemens as a measure)
Tiny changes in sweat gland activity cause rapid changes in skin electrical resistance
The more people sweat, the easier it is to conduct electricity across the skin (or the lower the resistance: why you don’t chuck a plugged-in kettle into your bathtub)
The sweat glands are controlled by the sympathetic nervous system and GSR can therefore measure subtle “fight or flight” type responses
GSR & refractory periods
When the sympathetic nervous system is activated by a stimulus (e.g. a fear provoking stimulus) it takes a little while to return to baseline (the refractory period)
So activity from previous stimuli can ‘contaminate’ later measures unless an appropriate time period is left between stimuli (an ‘Inter-Stimulus Interval, or ISI)
Breska, Maoz, & Ben-Shakhar (2011): random ISI between 8 & 12 s with a mean of 10 is sufficient: 16-24s (mean 20) gave slightly clearer results
Important to use a random ISI to prevent anticipatory responses
Heart Rate and ECG
Normal resting heart rate for healthy adults is between 70 and 75 beats per minute.
Heart rate is controlled by the autonomic nervous system
It can be measured by hand – i.e. by physically taking a pulse (inaccurate) - or electronically
ECG measurements record the whole of the cardiac cycle and allow a very accurate beat-to-beat measure
The Electrocardiogram
(Look at Powerpoint)
The Polygraph or ‘Lie Detector
The polygraph usually consists of:
GSR
Heart Rate
Respiration
Blood pressure
Ask 3 types of question requiring a yes/no response
Irrelevant
e.g. ‘Is your favourite colour red?’
Probable-lie control questions that most people will lie about
e.g. ‘Have you ever taken something that wasn’t yours?’
Relevant
e.g. ‘Did you steal the £10,000?’
The test is passed if the physiological responses during the Probable-lie questions is greater than during the Relevant questions
Example 1: guilt and innocence
Gamer et al. (2008) reported a study investigating the effectiveness of polygraph test in determining guilt, using a mock crime of theft
Method
Participants
108 participants in 3 groups:
‘guilty’ committed a mock-theft;
‘innocent-aware’ witnessed the theft
‘innocent-unaware’
Measured
Heart rate and GSR were measured while participants answered ten questions like this:
“What colour was the carpet in the room you stole the 50 EUR from? Was it … a) blue?, b) white?, c) yellow?, d) green?, e) red?, f) black?”
Participants were instructed to answer “no” each time, although one of the answers was relevant
Results
(Look at Powerpoint)
Conclusions from Gamer et al. (2008)
Significant differences between responses to relevant and irrelevant items were found for the “guilty” and “informed innocent” groups, with no such difference for the “innocent” group
The similarity between data for “guilty” and “informed innocent” groups suggests that the knowledge of crime details is a more important determinant of response than is actual execution of the crime.
Example 2: chocolate cravers
Rodriguez et al (2005) investigated the subjective and physiological reactivity to pictures of chocolate in high and low chocolate cravers
Method Participants 36 low and 36 high chocolate craving women Elicited a startle response and shown pictures Chocolate pictures Neutral Pictures Measured: GSR
Results
High cravers showed higher arousal to pictures of chocolate compared to neutral images
Low cravers showed the opposite
Conclusion:
High cravers show a selective arousal to images of chocolate that indicates that a distinct physiological/motivational state underlies the experience of chocolate craving
Does the Polygraph work?
BPS Report (2004) ‘A review of the current scientific status and fields of application of Polygraphic Deception Detection’
Identification of deception in criminal investigations is fairly high but incorrect decisions are ‘far from negligible’
Use of ‘countermeasures’ can be effective
No justification for its use in employment or security screening
Ethical issues
i.e. It works, but not well enough to be relied upon and can be easily fooled
Autonomic measures - summary
Provide a direct measure of physiological responses to a stimulus that can be very subtle
Difficult to fake, objective and quantifiable
Make sure you are as certain as possible about which emotion you are eliciting – these measures do not allow you to distinguish them
Avoid significant changes in room temperature – hot rooms will make people sweat more
Be aware that habituation will occur as you show more and more stimuli
You will need a good sample of participants – Example 1 used 108 women, but many studies use 20-40.
Central Nervous System Measures
The electroencephalogram (EEG) was discovered by Hans Berger in 1924
The dominant rhythm in the awake adult EEG, the ‘alpha rhythm’
originates from synchronous electrical activity in the dendrites of pyramidal cells of the neocortex
Approximately 6cm2 required to synchronise to generate EEG measurable at the scalp
EEG can tell you:
Broadly, where activity is taking place (localisation of function), but less precisely than e.g. fMRI, PET, MEG
Importantly: EEG can tell you what kind of activity’s going on…
EEG changes during sleep: different frequencies indicate different ‘states
(Look at Powerpoint)
EEG frequencies in the waking brain: again, different activity frequencies indicate states
(Look at Powerpoint)
Example 3: depression and the EEG
Henriques and Davidson (1993) compared the EEG of people with depression with that of undepressed controls
Left sided activation is associated with ‘approach’ behaviour
Right sided activation is associated with ‘avoidance’ behaviour
Method
Participants
15 patients and 13 controls
Measured
EEG power of different frequency bands at different electrode sites
Results
Depressed patients showed greater Alpha power at left frontal sites than at right frontal sites
This was the opposite pattern to controls
Conclusion:
Depressed patients show a deficit in the neural mechanisms underlying ‘approach’ behaviours
Alpha inhibition hypothesis: high alpha is indicative of inhibition and disengagement of task irrelevant brain areas (Klimesch et al., 2007)
VEP practical from a few years ago…
(Look at Powerpoint)
Pattern reversal condition (alternating)
(Look at Powerpoint)
VEP measured using Biopac in the labs…
(Look at Powerpoint)
Example 4: Ecstasy users and event-related potentials
Burgess et al.(2011) investigated the event-related potentials of people performing a word recognition memory test
Method Participants 15 ecstasy + cannabis users 14 cannabis users 13 non-drug using controls Measured Event-related potentials in a face recognition memory task
Results
The ERP component associated with recollection was attenuated in ecstasy users
Conclusion
Ecstasy users show a durable abnormality in a specific ERP component thought to be associated with recollection
EEG Measures - Summary
EEG
Provides a direct measure of brain state that can provide useful information about:
Arousal
Attention
Affect
Event-related Potentials
Provide a direct measure of the brain’s responses to a stimulus that can be very subtle
Both methods are objective, quantifiable and difficult to fake
Ethical Considerations
Electrical equipment, especially when attached to a person, must be safety tested and used correctly
If used incorrectly there is a risk of cross infection
What do you do if you find a physiological abnormality?
e.g. abnormal heart rhythm
Some participants, for example young children, do not necessarily like to be touched or have things stuck to them
There is some restriction of movement
e.g. don’t blink or move your face during EEG
People need to be informed about what you are measuring, and that it may be an unconscious response.
Confounding variables: moving!
EEG can’t tell the difference between muscle and brain activity
So if you speak or even move your mouth (or wiggle your ears/move your scalp) this could be a confounding variable
If you see a lot of unusual spikes in your data (like below) this may be blinking or moving. Consider starting the data collection again!
