As Valentine's Day approaches, many single people begin to feel a little sorry for themselves. On a day【C1】______by couples, this can lead to feelings of【C2】______and loneliness, say researchers.【C3】______, don't worry—they say it could【C4】______be good for you. "On the【C5】______of everyday life, it is understandable how something as personally【C6】______as loneliness could be regarded as a plague on human existence," John Cacioppoat and his fellow researchers at the University of Chicago write in the journal Cognition & Emotion. "Research【C7】______the past decade suggests a very different view of loneliness than suggested by personal experience, one in which loneliness【C8】______a variety of adaptive functions in【C9】______habitats." "Although it may feel like loneliness has no redeeming【C10】______, it promotes behavior change to increase the likelihood of the survival of one's genes. The pain of loneliness served to【C11】______us to renew the connections we needed to ensure survival and to promote social trust, co-hesiveness, and collective action." However, there was also bad news—researchers found the 'lonely' are viewed more negatively in terms of their psychosocial functioning and attractiveness. "In a social environment non-lonely people form a negative impression【C12】______lonely people, which then affects their behavior and【C13】______the lonely individual's perceived isolated existence," the researchers wrote. "【C14】______, individuals rated opposite-gender partners who they expected to be lonely as less sociable, and【C15】______towards them in a less sociable【C16】______than they did toward partners they expected not to be-lonely." The team even say loneliness could be behind many sports fans decision to【C17】______their team. "The emergence of a collective connectedness factor underlying loneliness, therefore, suggests that we may have evolved the capacity for and motivation to form relationships not only with other individuals but also with groups (e.g., a Chicago Cubs or Boston Red Sox fan), with the【C18】______being the promotion of co-operation in【C19】______conditions (e.g., competition, warfare). The identification with and investments in the group, in turn, may increase the likelihood of the continuity of the group, its members, and their individual genetic【C20】______."