According to the music and social bonding (MSB) hypothesis, human musicality has evolved as a mechanism supporting social bonding. The MSB hypothesis assumes that musicality relies on multiple neurocognitive components, which likely evolved to facilitate social bonding, although some components may also be used for non-social purposes such as individual mood regulation. The social function of music, or social bonding, as proposed by the MSB hypothesis, can be better understood under the lens of amnesia. Here, we argue that patients with amnesia, especially those with Alzheimer's disease, can benefit from music to retrieve personal (i.e., autobiographical) memories and, critically, to use these memories and music in general as a tool for social bonding.

Autobiographical memory is negatively affected by Alzheimer's disease and patients typically suffer difficulties in retrieving personal memories, especially specific personal memories situated in time and space (El Haj, Antoine, Nandrino, & Kapogiannis, Reference El Haj, Antoine, Nandrino and Kapogiannis2015; El Haj, Roche, Gallouj, & Gandolphe, Reference El Haj, Roche, Gallouj and Gandolphe2017). However, research has demonstrated that autobiographical memory decline can be somewhat alleviated, at least at the mild stage of the disease, by exposure to music. Research has demonstrated that music significantly increases the quantity and quality of autobiographical retrieval in patients with Alzheimer's disease (El Haj, Clément, Fasotti, & Allain, Reference El Haj, Clément, Fasotti and Allain2013; El Haj, Postal, & Allain, Reference El Haj, Postal and Allain2012; Irish et al., Reference Irish, Cunningham, Walsh, Coakley, Lawlor, Robertson and Coen2006). The positive effects of music exposure on the autobiographical memory of patients with Alzheimer's disease can be attributed to the involuntary nature of music-evoked autobiographical memories, that is, they are retrieved with little cognitive control and are thus automatic and bypass strategic processes during retrieval (El Haj, Fasotti, & Allain, Reference El Haj, Fasotti and Allain2012; Strollo & Romano, Reference Strollo, Romano and Marone2016).

We believe that music-evoked autobiographical memories can help patients with Alzheimer's disease to share their personal experience with the social environment. Recollecting personal memories from one's life thanks to music exposure helps patients to think, talk, or teach about past experiences (El Haj & Antoine, Reference El Haj and Antoine2016; Strollo & Romano, Reference Strollo and Romano2015). This assumption is supported by reminiscence theories according to which autobiographical retrieval has a social function, because sharing personal memories may (1) promote bonding between older adults, and (2) help in teaching others, especially the younger generation, about past experiences (Cappeliez, Rivard, & Guindon, Reference Cappeliez, Rivard and Guindon2007; Webster, Reference Webster1993; Westerhof & Bohlmeijer, Reference Westerhof and Bohlmeijer2014). Thus, music-evoked autobiographical memories may be used by patients with Alzheimer's disease to connect to others and to transmit their personal experiences and life lessons to others, including to younger adults. Music exposure may also help patients with Alzheimer's disease to share self-defining memories, that is, those vivid, emotionally intense, and repeatedly retrieved memories that reflect enduring concerns in a patient's life. For example, music exposure was shown to cue self-defining memories in patients with Alzheimer's disease (El Haj, Antoine, Nandrino, Gely-Nargeot, & Raffard, Reference El Haj, Antoine, Nandrino, Gely-Nargeot and Raffard2015). Thus, music exposure can promote retrieval of memories that provide patients with Alzheimer's disease with a sense of purpose, continuity, and meaning in the situations they encounter, as well as with a better understanding of both the self and the world.

Autobiographical retrieval can, therefore, help patients make sense of the past and present, and then to share it with others to create a social bond. The sharing of narratives serves a dual purpose: on the one hand, it promotes self-expression by means of personal stories, and on the other, it increases social bonding. Ultimately, social bonding acts as a kind of “social glue,” enabling patients with Alzheimer's disease to form social bonds with other patients and with younger people that they might otherwise not have created. These intra- and inter-generational bonds can be facilitated by the positive effects of music exposure on language, that is, it may enhance the ability of patients to produce complex linguistic structures, such as well-formed grammatical sentences, to describe their autobiographical memories.

To summarize, exposure to music can increase the quantity and quality of autobiographical retrieval in patients with Alzheimer's disease, thereby fueling their narrative with others to strengthen and maintain bonds. As suggested by the MSB hypothesis, music has a key social role to play, that is, to forge and reinforce affiliative inter-individual relationships. We believe that this is also the case for patients with Alzheimer's disease, who can use music-evoked autobiographical memories to share, tell, and/or teach others about these personal experiences. Music-evoked autobiographical memories can help patients with Alzheimer's disease to cement their social identity and reinforce group membership. We, thus, suggest that the MSB hypothesis could be extended to include music-evoked autobiographical memories in patients with Alzheimer's disease.