Recent research examines the possible neurological bases for such differences using brain imaging and other techniques. Multiple differences have been found in various regions of the brain, including in the limbic system, which is known to be involved in emotion.
Many of these differences arise in the amygdala, a small part of the limbic system. Differences in brain activity do not necessarily imply a concrete causal link to behavioral differences or a genetic difference in neural connections; hormones and experience also play a role in determining brain activity and behavior.
In a 2001 Gallup Poll, 90% of American adults viewed women as "more emotional" than men, but the survey did not ask for any specific associations for the word “emotion”. Scientists in the field distinguish between emotionality and the expression of emotion: Associate Professor of Psychology Ann Kring said, "It is incorrect to make a blanket statement that women are more emotional than men, it is correct to say that women show their emotions more than men." .
Kring performed an intensive research study on emotion, where emotion was measured by looking at expression, experience and physiological changes among the research subjects. Participants in the study viewed clips from popular movies divided into five categories - sad, happy, fear/disgust, anger and neutral. The first study examined the emotional responses of men and women to determine whether women are "more emotional" or whether they are just more emotionally expressive.
The second study examined family expressiveness and gender role to determine whether these characteristics can help to account for expressive differences between men and women. In both studies, women were found to be more facially expressive than men when it came to both positive and negative emotions. These researchers concluded that men and women experience the same amount of emotion, but that women are more likely to express their emotions.
Furthermore, the causes of sex differences in emotion or the expression of emotion are not known. Some evidence suggests a role for hormones. There is also extensive research into neurobiological differences that might be related to sex differences in emotion. But neither of these answer the "nature vs nurture" question with regard to the cause of sex differences in emotion.
In addition to biological differences between men and women, there are also documented differences in socialization that could contribute to sex differences in emotion and to differences in patterns of brain activity. An American Psychological Association article states that, “boys are generally expected to suppress emotions and to express anger through violence, rather than constructively” .
Young children look up to their parents as role models and to seek guidance. For instance, a young boy is often taught to act tough and be protective, and to refrain from crying. From this they form ideas that they should refrain from showing emotion. Then, later in life, after they are taught to be unemotional, society chastises them for being insensitive.
A child development researcher at Harvard University, points to what he calls society's "emotional miseducation" of boys.. This implies that boys are taught to shut down their feelings, such as empathy, sympathy and other key components of what is deemed to be pro-social behavior. According to this view, differences in emotionality between the sexes are theoretically only socially-constructed, rather than biological.
The following brain structures are currently thought to be most involved in emotion: the amygdala, prefrontal cortex, anterior cingulate, ventral striatum, and insula. Research has shown that, when viewing emotional movies, the amygdala exerts a “positive influence” on the ventrolateral prefrontal cortex, which is involved in successfully remembering events.
The amygdala also shows increased communication to other areas involved in memory during emotionally arousing events.
Although both men and women show increased outflow from the amygdala in emotional situations, the amygdala communicates with different areas of the brain in men and women. In men, the amygdala connects to regions that promote a response to external stimuli, like the visual cortex.
In women, the amygdala connects to regions that monitor and regulate conditions within the body, like the hypothalamus. Women show a significantly greater activity in the left amygdala when encoding and remembering emotionally arousing pictures (such as mutilated bodies ) than do men, while men show greater activity in the right amygdala.
Men and women tend to use different neural pathways to encode stimuli into memory. While highly emotional pictures were remembered best by all participants in one study, as compared to emotionally neutral images, women remembered the pictures better than men. This study also found greater activation of the right amygdala in men and the left amygdala in women.
Women generally use the left amygdala to process emotional experiences, which has been proposed to help them remember details about events. Men generally use the right amygdala to process emotional experiences and remember more of the central ideas about events.
On average, women use more of the left hemisphere when shown emotionally arousing images, while men use more of their right hemisphere. Women also show more consistency between individuals for the areas of the brain activated by emotionally disturbing images. Activations of emotionally significant areas differ between men and women when shown arousing pictures. In men, six out of eight activations were in the right hemisphere, while all activations in women were in the left hemisphere.
Another study reported that women’s brains show more activity overall when they are shown images meant to provoke emotional responses – 9 areas involved in emotion are activated in women, while only 2 areas are activated in men. On average, women's brains show more activity than men's brains when they recall grief or sad events.
When women are asked to think about past events that made them angry, they show activity in the septum in the limbic system; this activity is absent in males. In contrast, men's brains show more activity in the limbic system when asked to identify happy or sad male and female faces. Men and women also differ in their ability to recognize sad female faces: in one study, men recognized 70%, while women recognized 90%.
Responses to pain also reveal sex differences. In women, the limbic system, which is involved in the processing of emotions, shows greater activity in response to pain. In men, cognitive areas of the brain, which are involved in analytical processing, show higher activity in response to pain. This indicates a connection between pain-responsive brain regions and emotional regions in women.
It is generally assumed that differences in brain structure between various groups relate to or drive expressed differences in behavior. However, brain remodeling also occurs based on experience; this phenomenon opens up the possibility that observed brain differences may not be genetically programmed but instead arise from experience and the use of specific regions for specific tasks.
By age 18, women cry 4 times more than men, possibly because of higher levels of prolactin in women. Prolactin is present in tears and contributes to the amount of crying a person does. The difference in levels of crying between men and women could also be the result of cultural expectations.
Oxytocin may be linked to the formation of romantic bonds as well as bonds of mothers to infants in some species. In humans, oxytocin receptors are located in areas of the brain that are rich in dopamine receptors, which could result in pleasurable neurological reward in response to the release of oxytocin.
In prairie voles, where oxytocin receptors also overlap with dopamine receptors, the presence of oxytocin in the brain's "reward pathways" plays an important role in monogamous pair-bonding. Oxytocin also helps reduce stress, at least in women - estrogen seems to enhance the "feel-good" properties of oxytocin by inhibiting the release of adrenalin and other "stress" hormones.