Cerebral (brain) lateralization of cognition and emotion
What is Lateralization?
The idea that the right and left hemispheres of the brain (cerebral cortex) are structurally and functionally asymmetrically, wherein some specific functions are controlled more by (or entirely by) one hemisphere than the other, is called ‘cerebral lateralization’.
BRAIN LATERALIZATION OF COGNITIONS
BRAIN LATERALIZATION OF EMOTIONS
The Right-Hemisphere Hypothesis
In 1912, Mills observed that damage to the right side of the head caused a decrease of the emotional expression. Similarly, Babinski (1914) verified that patients with lesions in the right hemisphere became manic or emotionally indifferent. These initial studies led to the development of the right hemisphere hypothesis, which that the left hemisphere is associated with cognitive processes, whereas the right hemisphere is involved with the processing of emotion.
Sackeim, Gur and Saucy (1978) found that facial expressions are more intensely expressed in the left side of the face, suggesting a greater involvement of the right hemisphere in the production of emotional displays.
Adolphs, Damasio, Tranel and Damasio (1996) verified that patients with right hemisphere damage were more impaired in recognizing facial expressions than patients with left hemisphere damage.
Some authors have also suggested that the right hemisphere might contain a store of structural representations or templates of facial expressions.
Once these templates are destroyed, by a stroke or cerebral injury for example, the capacity to recognize facial expressions could be lost.
The Valence Hypothesis
This model proposes that the pattern of hemispheric dominance depends on the emotional valence of the stimulus.
The left hemisphere is dominant for processing positive emotions whereas the right hemisphere is dominant for processing negative emotions.
Goldstein (1939) showed that damage to the left hemisphere was more likely to cause a severe depressive reaction in psychiatric patients than damage to the right hemisphere.
Sackeim et al. (1982), reviewed 109 cases of pathological
laughing and crying, and found evidence suggesting that a damage to left hemisphere led to the onset of depressive symptoms in psychiatric patients.
On the other hand, damage to the right hemisphere was more frequently associated to a pathological laughing condition.
According to the valence hypothesis, fear, anger, disgust and sadness are considered negative emotions, and happiness and surprise are classified as positive emotions.
The Approach/ Withdrawal Hypothesis
According to this approach, the left hemisphere specializes in approach behaviours related to emotional processing, whereas the right hemisphere specializes in withdrawal behaviours.
It has its foundation in the relationship between motivation and emotion.
According to the approach-withdrawal hypothesis, happiness, surprise, and anger are classified as approach emotions, since they indicate a drive of the individual toward the environmental stimuli.
On the other hand, sadness, fear and disgust are associated with withdrawal behaviours, because they tend to lead the individual away from the environmental sources of aversive stimulation.