Lecture 6
Emotion, Motivation and Brain Lateralisation
The Right Hemisphere Hypothesis:
The earliest hypothesis was proposed by Hughlings-Jackson (1874).
o The Right Hemisphere Hypothesis: suggests that the right cerebrum is
dominant for processing all emotions regardless of the affective valence.
o The left hemisphere is the logical part of the brain, e.g. chess. Whereas right
half is the creative side; the emotional side.
o This had a profound cultural impact, but there isn’t a lot of evidence for it.
Evidence for the Right Hemisphere being more Emotional:
Ross & Monnot (2008): when you suffer a stroke in the left hemisphere you can
develop aphasia (language production and comprehension problems). When you
brain damage in the right hemisphere, this results in more subtle impairments in
the emotional components of language (e.g. saying a sentence in an angry way).
Right hemisphere of the brain appears critically important in emotion, and in
this context through speech and language.
Lindell (2013): Lower 2/3rds of the face are innervated contra-laterally.
o The left motor cortex controls the right face
o And the right motor cortex controls the left side of the face.
o Round the eyes is more bilateral.
o So if the right hemisphere is dominant for emotion, the left side of the face
should be more expressive than the right side.
o This was the case. Chimeric faces composed of mirrored left cheeks appear
more expressive than mirrored right cheek composites.
Evidence Against:
The left-face (RH) is more pronounced for negative than for positive emotions.
This suggests that there is no absolute right hemisphere lateralisation.
Rather, there may be some statistical specialisation that may depend on the
particular emotion at hand.
The Valence Hypothesis:
The processing of pleasant stimuli is left lateralised in the brain.
Whereas the processing of unpleasant stimuli is right lateralised.
Particularly in the prefrontal regions.
Evidence for The Valence Hypothesis:
Robinson et al (1988): mood disorders following cerebrovascular brain injury
(stroke)
o Lots of patients develop mood disorders following strokes.
o Undertook a detailed neuropsychiatric interview to detect the presence of
mood disorder.
o Found that patients who developed secondary mania (elation) all had right
hemisphere damage.
o Patients who developed major depressive disorder, had damage to the left
frontal cortex.
Emotion, Motivation and Brain Lateralisation
The Right Hemisphere Hypothesis:
The earliest hypothesis was proposed by Hughlings-Jackson (1874).
o The Right Hemisphere Hypothesis: suggests that the right cerebrum is
dominant for processing all emotions regardless of the affective valence.
o The left hemisphere is the logical part of the brain, e.g. chess. Whereas right
half is the creative side; the emotional side.
o This had a profound cultural impact, but there isn’t a lot of evidence for it.
Evidence for the Right Hemisphere being more Emotional:
Ross & Monnot (2008): when you suffer a stroke in the left hemisphere you can
develop aphasia (language production and comprehension problems). When you
brain damage in the right hemisphere, this results in more subtle impairments in
the emotional components of language (e.g. saying a sentence in an angry way).
Right hemisphere of the brain appears critically important in emotion, and in
this context through speech and language.
Lindell (2013): Lower 2/3rds of the face are innervated contra-laterally.
o The left motor cortex controls the right face
o And the right motor cortex controls the left side of the face.
o Round the eyes is more bilateral.
o So if the right hemisphere is dominant for emotion, the left side of the face
should be more expressive than the right side.
o This was the case. Chimeric faces composed of mirrored left cheeks appear
more expressive than mirrored right cheek composites.
Evidence Against:
The left-face (RH) is more pronounced for negative than for positive emotions.
This suggests that there is no absolute right hemisphere lateralisation.
Rather, there may be some statistical specialisation that may depend on the
particular emotion at hand.
The Valence Hypothesis:
The processing of pleasant stimuli is left lateralised in the brain.
Whereas the processing of unpleasant stimuli is right lateralised.
Particularly in the prefrontal regions.
Evidence for The Valence Hypothesis:
Robinson et al (1988): mood disorders following cerebrovascular brain injury
(stroke)
o Lots of patients develop mood disorders following strokes.
o Undertook a detailed neuropsychiatric interview to detect the presence of
mood disorder.
o Found that patients who developed secondary mania (elation) all had right
hemisphere damage.
o Patients who developed major depressive disorder, had damage to the left
frontal cortex.
