Summary Psychophysiology and affective computing (0HM320)
Lecture 1 Introduction Psychophysiology and skin conductance measurement – psycho
Psychophysiology: based on idea that aspects of the mind have a physical substrate that we can
measure
- Physiology helps in understanding psychology: provides ways of measuring psychological
processes, helps understanding interplay between mind and body, provides new questions
- Disadvantages psychophysiology: is it true that everything in the mind has a physical
substrate? Hard to measure the mind directly, you could add a third aspect like measuring
behavior (triangulation) and try to see which measure is most in line with it
Physiology:
- Physiological parameters: cardiovascular parameters (heart rate, blood pressure),
respiration parameters, skin temperature
- All parameters are controlled by the nervous system: Central nervous system (CNS),
peripheral nervous system (PNS), Somatic (gives control over what we do), autonomic (we
do not have control over it, regulates our functioning itself) which consists of two parts:
Sympathetic (SNS): in first part acetylcholine (fast) where all nerves react
together, in second part norephinephrine slower, fight or flight response,
triggers the proper organs for action, includes sweat gland
Parasympathetic (PsNS): acetylcholine neurotransmitter, rest or digest
system, triggers organs to rest from activity or to digest food
Measuring skin conductance (physiological part I):
- Electrodynamics:
o Voltage (V): electrical potential difference between two spots
o Ohm’s Law (if there is a current between spots): V=I*R
o Conductance (C): C=1/R=I/V unit is Siemens (S) or microsiments (uS)
o Electrodermal activity (EDA/GSR) uses these things, history:
Tarchanoff: measuring changes in electrical potential between electrodes on
skin (endosomatic)
Vigouroux & Charcot: exosomatic, passing current through skin and
measure inscreases in skin conductance in response to different stimuli
Darrow: correlation SC and sweat glad activity, SC changes before sweat is
secreted
Exosomatic with fixed voltages is preferred today
- Sweat glands in deeper layer of skin, two types:
o Apocrine: not well studies
o Eccrine: functions are thermal regulation (most of the body), grasping behavior
(getting a better grip due to more friction by moist)
o Sweat ducts can be modelled as resistors in parallel
Bigger distance between electrodes=lower conductance
Bigger electrodes, higher gland density = higher conductance
More sweat in ducts = higher conductance, content of sweat in duct is what
you measure with SC
o Sweat glands are controlled by the Sympathetic nervous system (SNS) only, even
though the neurotransmitter involved is acetylcholine, which is mostly related to
1
, PsNS. Convincing evidence: a correlation was found between EDA activity and SNS
potentials measured in nerves
- 3 pathways influencing EDA:
o Hypothalamus and limbic system (ipsilateral = brain side and body side of activation
are the same)
o Basal ganglia and cortex (contralateral – brain side and body side of activation are
opposite left-right right-left )
o Reticular formation (brainstem)
- Measuring skin conductance
o Fixed devices, holter devices, wearables
o You need electrodes to pick up the signals, earlier AG-AGCl were used, now dry
electrodes are used or self-adhesive with gel
o Positioning of SC electrodes: on hand (many sweat glands), wrist, foot, they all give
different values. Put electrodes on non-dominant hand (avoid cuts, leaves dominant
hand free for task and less movement interference). But both sides of the body do
not give the same SC: SC in emotions (limbic system ipsilateral reaction), non-
emotion (contralateral reaction) can give different reactions, so the amount of skin
conductance on each side depends on where the brain signal originates
o Skin conductance signal
Skin conductance responses (SCR): look at one individual peak, responses to
specific stimuli, peaks without stimuli are on-specific SCR
Skin conductance level (SCL): average level of responses over multiple
stimuli, most used, between 2 and 20 uS
Correlation of .6 between most SC measures, only SCR rise time and SCR half
recovery time are highly correlated
o Use means of repeated stimulus: SCR amplitude (mean of amplitudes of the peaks),
SCR magnitude (mean of SCR amplitudes expected after each stimulation, take into
account amplitudes of 0 when no reaction). The values often don’t have a normal
distribution you can normalize it by taking the log or the square root
o SCR habituation: reaction to repeated stimuli will get less: trials to habituation (how
often do you need to present the stimulus till there is no reaction, trials interaction
or main effect in Anova, regression slope of SCR against stimulus number
o Comparing effects between individuals: large difference between individuals,
correction of intra-individual differences:
Correct SCL for range: SCLcor = (SCL- SCLmin)/(SCLmax - SCLmin)
Z-transformation: SCLcor = (SCL - SCLmean)/stdev(SCL)
Measuring an additional baseline: SCLcor = SCLstimulus – SCLbaseline
- Advantages of EDA: SCR reactions are easily seen, quick in responding (compared to HR),
completely sympathetic, general arousal indicator
- Disadvantages of EDA: slow in responding (compared to EEG in brain), reacts to different
types of stimuli (also reacts to for example exercise)
2
, Lecture 2 Skin conductance (psychological part II) – psycho
Differences within persons, factors influencing EDA.
Discrete stimuli (mostly SCRs):
- Lie detector/polygraph: monitors SC, but also HR, respiration, blood pressure. Only applied
in strict protocol to avoid false positivesGuilty knowledge test, more excitation when
lying, guilty 90% correct, innocent 100%
- Classical conditioning (Pavlov): dog has physiological reaction to the sound because this is
conditioned to the food. After point of awareness clear distinction between high and low
tone
o Conditioning with people: People were presented with different tones and some
were followed by a shock. After people realized what tone was followed by a shock
(CS+), there SCR magnitude went up when they heard that tone. Extinction starts
when CS+ is no longer followed by shock (sometimes explicitly mentioned): SCRs still
follow CS+, but less and less. SCR conditioning lasts beyond point of cognitive
extinction (body adapts slower). Extinction takes longer for biologically prepared,
fear-relevant stimuli (pictures of snakes, spiders, guns, angry faces). Even when
stimuli were masked, they still elicited a reaction
- Pictures are used a lot as discrete stimuli (IAPS), organized according to valence and arousal
dimensions. SC is linked to the arousal dimensions, not to valence dimension. SC is higher
when arousal is higher, but you don’t know it is positive or negative
- Orienting response (OR): our reaction to something in our environment, involves SCR, kicks
in in case of novelty (nieuwschierigheid) or significance (e.g. shock)
Continuous stimuli/sustained tasks (mostly #NS-SCRs & SCL):
- Different types: e.g listening to noise, math, watching film clips. Often increase in SCL or NS-
SCR in anticipation of task (non-specific responses, as it is not one event), steep increase at
the start of the task, gradually decay during task (initial excitement decreases over
time)arousal ensures effortful allocation of resources
- Social stimulation: if two or more persons are involved, SC traces can also be compared in
time (linkage), the meaning of this linkage differs per situation.
o During therapeutic interviews: more increase in NS-SCR when therapist is perceived
as less tolerant. More linkage (almost same SC signal) between therapist and patient
when a patient likes the session. Married discussing an issue: if married was
distressed the SCL was higher during discussion, more linkage in distressed marriage
Individual characteristics (between persons):
- Electrodermal lability: high NS-SCR and/or slow SCR habituation, this is relatively reliable
over time. Generally labiles outperform stabiles in: sustained vigilance, perceptual speed,
allocation of information processing, focusing attention on task
- Electrodermal non-responder: showing no SCR at all at mild innocuous tones, occurs in 10%
of population. Higher percentage among schizophrenia patients (40-50%), relatively stable
response over weeks, but not over years
- (Tonic) Hyperarousal: high SCL, high NS-SCR. Found in schizophrenics with psychotic
symptoms, not during remission. More present when relatives are critical (enhances chances
of relapse). Found more in 1st degree relatives of schizopherincs (erfelijk)
- Psychopaths and antisocial behavior, mostly measured in males:
3
Lecture 1 Introduction Psychophysiology and skin conductance measurement – psycho
Psychophysiology: based on idea that aspects of the mind have a physical substrate that we can
measure
- Physiology helps in understanding psychology: provides ways of measuring psychological
processes, helps understanding interplay between mind and body, provides new questions
- Disadvantages psychophysiology: is it true that everything in the mind has a physical
substrate? Hard to measure the mind directly, you could add a third aspect like measuring
behavior (triangulation) and try to see which measure is most in line with it
Physiology:
- Physiological parameters: cardiovascular parameters (heart rate, blood pressure),
respiration parameters, skin temperature
- All parameters are controlled by the nervous system: Central nervous system (CNS),
peripheral nervous system (PNS), Somatic (gives control over what we do), autonomic (we
do not have control over it, regulates our functioning itself) which consists of two parts:
Sympathetic (SNS): in first part acetylcholine (fast) where all nerves react
together, in second part norephinephrine slower, fight or flight response,
triggers the proper organs for action, includes sweat gland
Parasympathetic (PsNS): acetylcholine neurotransmitter, rest or digest
system, triggers organs to rest from activity or to digest food
Measuring skin conductance (physiological part I):
- Electrodynamics:
o Voltage (V): electrical potential difference between two spots
o Ohm’s Law (if there is a current between spots): V=I*R
o Conductance (C): C=1/R=I/V unit is Siemens (S) or microsiments (uS)
o Electrodermal activity (EDA/GSR) uses these things, history:
Tarchanoff: measuring changes in electrical potential between electrodes on
skin (endosomatic)
Vigouroux & Charcot: exosomatic, passing current through skin and
measure inscreases in skin conductance in response to different stimuli
Darrow: correlation SC and sweat glad activity, SC changes before sweat is
secreted
Exosomatic with fixed voltages is preferred today
- Sweat glands in deeper layer of skin, two types:
o Apocrine: not well studies
o Eccrine: functions are thermal regulation (most of the body), grasping behavior
(getting a better grip due to more friction by moist)
o Sweat ducts can be modelled as resistors in parallel
Bigger distance between electrodes=lower conductance
Bigger electrodes, higher gland density = higher conductance
More sweat in ducts = higher conductance, content of sweat in duct is what
you measure with SC
o Sweat glands are controlled by the Sympathetic nervous system (SNS) only, even
though the neurotransmitter involved is acetylcholine, which is mostly related to
1
, PsNS. Convincing evidence: a correlation was found between EDA activity and SNS
potentials measured in nerves
- 3 pathways influencing EDA:
o Hypothalamus and limbic system (ipsilateral = brain side and body side of activation
are the same)
o Basal ganglia and cortex (contralateral – brain side and body side of activation are
opposite left-right right-left )
o Reticular formation (brainstem)
- Measuring skin conductance
o Fixed devices, holter devices, wearables
o You need electrodes to pick up the signals, earlier AG-AGCl were used, now dry
electrodes are used or self-adhesive with gel
o Positioning of SC electrodes: on hand (many sweat glands), wrist, foot, they all give
different values. Put electrodes on non-dominant hand (avoid cuts, leaves dominant
hand free for task and less movement interference). But both sides of the body do
not give the same SC: SC in emotions (limbic system ipsilateral reaction), non-
emotion (contralateral reaction) can give different reactions, so the amount of skin
conductance on each side depends on where the brain signal originates
o Skin conductance signal
Skin conductance responses (SCR): look at one individual peak, responses to
specific stimuli, peaks without stimuli are on-specific SCR
Skin conductance level (SCL): average level of responses over multiple
stimuli, most used, between 2 and 20 uS
Correlation of .6 between most SC measures, only SCR rise time and SCR half
recovery time are highly correlated
o Use means of repeated stimulus: SCR amplitude (mean of amplitudes of the peaks),
SCR magnitude (mean of SCR amplitudes expected after each stimulation, take into
account amplitudes of 0 when no reaction). The values often don’t have a normal
distribution you can normalize it by taking the log or the square root
o SCR habituation: reaction to repeated stimuli will get less: trials to habituation (how
often do you need to present the stimulus till there is no reaction, trials interaction
or main effect in Anova, regression slope of SCR against stimulus number
o Comparing effects between individuals: large difference between individuals,
correction of intra-individual differences:
Correct SCL for range: SCLcor = (SCL- SCLmin)/(SCLmax - SCLmin)
Z-transformation: SCLcor = (SCL - SCLmean)/stdev(SCL)
Measuring an additional baseline: SCLcor = SCLstimulus – SCLbaseline
- Advantages of EDA: SCR reactions are easily seen, quick in responding (compared to HR),
completely sympathetic, general arousal indicator
- Disadvantages of EDA: slow in responding (compared to EEG in brain), reacts to different
types of stimuli (also reacts to for example exercise)
2
, Lecture 2 Skin conductance (psychological part II) – psycho
Differences within persons, factors influencing EDA.
Discrete stimuli (mostly SCRs):
- Lie detector/polygraph: monitors SC, but also HR, respiration, blood pressure. Only applied
in strict protocol to avoid false positivesGuilty knowledge test, more excitation when
lying, guilty 90% correct, innocent 100%
- Classical conditioning (Pavlov): dog has physiological reaction to the sound because this is
conditioned to the food. After point of awareness clear distinction between high and low
tone
o Conditioning with people: People were presented with different tones and some
were followed by a shock. After people realized what tone was followed by a shock
(CS+), there SCR magnitude went up when they heard that tone. Extinction starts
when CS+ is no longer followed by shock (sometimes explicitly mentioned): SCRs still
follow CS+, but less and less. SCR conditioning lasts beyond point of cognitive
extinction (body adapts slower). Extinction takes longer for biologically prepared,
fear-relevant stimuli (pictures of snakes, spiders, guns, angry faces). Even when
stimuli were masked, they still elicited a reaction
- Pictures are used a lot as discrete stimuli (IAPS), organized according to valence and arousal
dimensions. SC is linked to the arousal dimensions, not to valence dimension. SC is higher
when arousal is higher, but you don’t know it is positive or negative
- Orienting response (OR): our reaction to something in our environment, involves SCR, kicks
in in case of novelty (nieuwschierigheid) or significance (e.g. shock)
Continuous stimuli/sustained tasks (mostly #NS-SCRs & SCL):
- Different types: e.g listening to noise, math, watching film clips. Often increase in SCL or NS-
SCR in anticipation of task (non-specific responses, as it is not one event), steep increase at
the start of the task, gradually decay during task (initial excitement decreases over
time)arousal ensures effortful allocation of resources
- Social stimulation: if two or more persons are involved, SC traces can also be compared in
time (linkage), the meaning of this linkage differs per situation.
o During therapeutic interviews: more increase in NS-SCR when therapist is perceived
as less tolerant. More linkage (almost same SC signal) between therapist and patient
when a patient likes the session. Married discussing an issue: if married was
distressed the SCL was higher during discussion, more linkage in distressed marriage
Individual characteristics (between persons):
- Electrodermal lability: high NS-SCR and/or slow SCR habituation, this is relatively reliable
over time. Generally labiles outperform stabiles in: sustained vigilance, perceptual speed,
allocation of information processing, focusing attention on task
- Electrodermal non-responder: showing no SCR at all at mild innocuous tones, occurs in 10%
of population. Higher percentage among schizophrenia patients (40-50%), relatively stable
response over weeks, but not over years
- (Tonic) Hyperarousal: high SCL, high NS-SCR. Found in schizophrenics with psychotic
symptoms, not during remission. More present when relatives are critical (enhances chances
of relapse). Found more in 1st degree relatives of schizopherincs (erfelijk)
- Psychopaths and antisocial behavior, mostly measured in males:
3
