term benefits such as promoting positive emotions and a relaxed environment. Endocrine effects Social grooming has shown to be correlated with changes in endocrine levels within individuals. Specifically, there is a large correlation between the brain's release of oxytocin and social grooming. Oxytocin is hypothesized to promote prosocial behaviors due to its positive emotional response when released. Further, social grooming also releases beta-endorphins which promote physiological responses in stress reduction. These responses can occur from the production of hormones and endorphins, or through the growth or reduction in nerve structures. For example, in studies of suckling rats, rats who received warmth and touch when feeding had lower blood pressure levels than rats who did not receive any touch. This was found to be a result of an increased vagal nerve tone, meaning they had had higher parasympathetic nervous response and lower sympathetic nervous response to stimulus, resulting in a lower stress response. Social grooming is a form of innocuous sensory activation. Innocuous sensory activation, characterized by non-aggressive contact, stimulates an entirely separate neural pathway from nocuous aggressive sensory activation. Innocuous sensations are transmitted through the dorsal column-medial lemniscal system. Oxytocin Oxytocin is a peptide hormone known to help express social emotions such as altruism, which in turn provides a positive feedback mechanism for social behaviors. For example, studies in vampire bats have shown that intranasal injections of oxytocin have increased the amount of allogrooming done by female bats. The release of oxytocin, found to be stimulated by positive touch (such as allogrooming), positive smells and sounds, can have physiological benefits to the individual. Benefits can include: relaxation, healing, and digestion stimulation. Further, reproductive benefits have been found such as studies in rats have shown that the release of oxytocin can increase male reproductive success. The role of oxytocin is important in maternal pair bonding, and is hypothesized to promote similar bonding in social groups as a result of positive feedback loops from social interactions. Beta-endorphins Grooming stimulates the release of beta-endorphin, which is one physiological reason for why grooming appears to be relaxing. Beta-endorphins are found in neurons in the hypothalamus and the pituitary gland. Beta-endorphins are found to be opioid agonists. Opioids are molecules that act on receptors to promote feelings of relaxation, and reduce pain. A study in monkeys shows the changes in opiate expression in the body, mirroring changes in beta-endorphin levels, influences desire for social grooming.