Physical appearance is the area of nonverbal communication most heavily researched. While the differences between the biologies of men and women give them different physiques, the sexual dimorphisms present in the human race are few compared to other animals. It is social constructs that lead to the exaggeration of appearance-related differences between men and women. The major similarities in physical appearance of both genders that tend not to hold true for other animals include body size, body hair and facial structure.
Results of research in proximics, the study of personal space and interpersonal distance, shows that men and women's concepts and use of personal space are particularly similar. While researchers in the past found that men tend to require more space than women, recent research shows that this difference is one of social power and not sex. In other words, women of high power also require more space, and men of low power require less space. The interpersonal distances men and women use for interactions with strangers, friends, family and lovers are the same in general.
Kinesics is the study of body movement and facial expressions. Clear similarities in this area of nonverbal communication are facial expressions and gestures. Men and women use the same types of facial expression to express the same emotions. There are no facial expressions that one sex uses that the other does not. Gestures are cross-gender as well. The differences found between the gestures men and women use are only the intensity and frequency of gesture use -- not the types of gestures used.
Though there are clear differences between the voices of men and women, there are many similarities as well. The differences in voice behavior can be attributed to two factors: hormones and social expectations. When both of these factors are controlled for, the male and female voice are nearly identical. It is only when puberty sets in and a child begins to pay attention to his or her gender role's social expectations that there are clear differences in vocalic behavior.