In our social interactions with others, there is often some touching involved, such as handshakes, hugs, pats, kisses, and so on. Clearly the limits are also influenced by the relationship of the two people and some things that are acceptable with friends may not be so with acquaintances. Complicating matters are gender and culture, with some societies seeking to eliminate contact entirely between strangers or acquaintances. This whole area is full of pitfalls that accompany inappropriate touching and I tend to take the cowardly way out and let the other person initiate the level of touch.
The journal Proceedings of the National Academy of Sciences published a paper by a team of researchers from Oxford University (UK), Aalto University (Finland), and the University of Turku (Finland) that looked into this question and the results are summarized in a nifty graphic. They obtained the data from a sample of 1,368 people in Finland, France, Italy, Russia, and the United Kingdom so the results really only apply to that part of the world. TAM stands for the ‘touch area map’ while TI stands for ‘touchability index’.
Here are some excerpts from the paper.
The time primates devote to grooming each other far exceeds the requirements of hygiene… it however remains unclear whether the relationship between social touch and interpersonal emotional bonds mainly reflects biologically driven bonding or culture-based normative behavior.
We show that the total bodily area allowed for touching is linearly dependent on the emotional bond with the toucher across a wide range of European cultures.
TAMs for different social network members were clearly separable. The partner was allowed to touch basically anywhere over the body, closest acquaintances and relatives over the head and upper torso, whereas strangers were restricted to touch only the hands. Taboo zones, where touching was not allowed, included the genitals for extended family and males in family, acquaintances, and strangers, as well as the buttocks for males in extended family, acquaintances, and strangers.
Finally, the sex of the participant and the toucher significantly influenced the TIs (Fig. 4). When considering social network members having the same type of social relationship with the participant (e.g., sister vs. brother), females were allowed to touch wider body areas than males. The sex-related TI differences were significant for all male–female pairs of the social network (P < 0.05, t test). Accordingly, participants also reported stronger emotional bonds with female than male members of their social networks (SI Appendix, Table S5). Moreover, female subjects reported, on average, higher TIs across all members of their social network than males did, with the exception of female acquaintances and female strangers. … A critical question is why the TAMs are so strongly relationship-dependent. One possibility is that the social relationship between people touching each other moderates the rewarding properties of social touch, which promotes or inhibits touching in different relationships. The TI was indeed positively correlated with the experienced pleasantness of touch, and the more pleasant a touch by an individual was felt, the larger body surface that individual was allowed to touch. Consequently, closer social relationships would allow larger capacity (i.e., total body area allowed for touching) for triggering pleasurable sensations. … Female, rather than opposite-sex, touch was, in general, evaluated as more pleasant, and it was consequently allowed on larger bodily areas. It is known that females allow themselves to be touched on a larger bodily area than males (see also ref. 35) and that female same-sex touch is allowed without discomfort on most of the body surface. Our findings agree with a number of early behavioral studies outlining females as touching and being touched more often (meta-analysis in ref. 36). The reason for this sex difference remains unclear. Primate studies indicate that female grooming relationships are fairly stable (2) and that re- lationship quality, serviced by grooming behavior, and longevity in female baboons do not correlate (37). Together, these findings support social touching, as a human equivalent of grooming, as a predominantly feminine-appropriate behavior (38).
It is not clear how useful this research is answering the practical question of what level of touch is appropriate when meeting someone, though.