For a recent review of the debates around kin recognition and their role in the wider debates about how to interpret inclusive fitness theory, including its compatibility with ethnographic data on human kinship, see Holland (2012). Leading inclusive fitness theorists such as Alan Grafen have argued that the whole research program around kin recognition is somewhat misguided:  Others have cast similar doubts over the enterprise:  Kin recognition is a behavioral adaptation noted in many species but proximate level mechanisms are not well documented. Recent studies have shown that kin recognition can result from a multitude of sensory input. Jill Mateo notes that there are three components prominent in kin recognition. First, "production of unique phenotypic cues or labels". Second, "perception of these labels and the degree of correspondence of these labels with a 'recognition template'", and finally the recognition of the phenotypes should lead to "action taken by the animal as a function of the perceived similarity between its template and an encountered phenotype". The three components allow for several possible mechanisms of kin recognition. Sensory information gathered from visual, olfactory and auditory stimuli are the most prevalent. The belding ground squirrel kin produce similar odors in comparison to non-kin. Mateo notes that the squirrels spent longer investigating non-kin scents suggesting recognition of kin odor. It's also noted that belding's ground squirrels produce at least two scents arising from dorsal and oral secretions, giving two opportunities for kin recognition. Auditory distinctions have been noted among avian species. Long-tailed tits ("Aegithalos caudatus") are capable of discriminating kin and non-kin based on contact calls. Distinguishing calls are often learned from adults during the nestling period. Studies suggest that the bald-faced hornet, "Dolichovespula maculata", can recognize nest mates by their cuticular hydrocarbon profile, which produces a distinct smell. Kin recognition in some species may also be mediated by immunogenetic similarity of the major histocompatibility complex (MHC). For a discussion of the interaction of these social and biological kin recognition factors see Lieberman, Tooby, and Cosmides (2007). Some have suggested that, as applied to humans, this nature-nurture interactionist perspective allows a synthesis between theories and evidence of social bonding and cooperation across the fields of evolutionary biology, psychology (attachment theory) and cultural anthropology (nurture kinship). Kin recognition is an adaptive behavior observed in living beings to prevent inbreeding, and increase fitness of populations, individuals and genes.