Relationships are of vital importance to our survival and well-being (Baumeister & Leary, 1995; Bowlby, 1969, 1973; Buss, 2003; Gilbert, 1989). One way in which we monitor the quality of our relationships and whether we are likely to be accepted or rejected by others is through non-verbal communications, primarily facial expressions (Darwin, 1872; Ekman & Friesen, 1971). Whilst there is much research on the processing of social threat signals and threatening facial expressions (Mogg & Bradley, 2002), research on the processing of facial expressions which convey safeness and altruism is scant. It is known that certain individuals have attentional biases toward threatening cues especially those conveyed through facial expressions. These same individuals tend to have diminished attentional focus toward positive cues such as happy facial expressions. This thesis explores how people process socially affiliative facial expressions, in particular those deemed compassionate. The processing of these facial expressions will be explored in relation to a variety of individual differences in mood, attachment, self-evaluation (namely self-criticism) and social rank. Chapters 1-3 of this thesis outline the background, aims and methodologies. Chapters 4-7 outline the four studies of this thesis which explore facial attentional processing in light of individual differences and primed positive and negative moods. Study 1 explores the processing of accepting and rejecting faces when participants are primed with compassionate, critical or no mental imagery; Study 2 develops and validates a new facial stimulus set displaying compassionate, critical and neutral facial expressions; Study 3 explores the attentional processing of these new compassionate and critical stimuli; Study 4 explores the attentional processing of compassionate and critical expressions when participants are primed with compassionate or critical Imagery. The first study showed that different types of imagery task and individual differences in self-esteem were associated with different attentional processing of accepting and rejecting facial expressions. However, participant feedback suggested that some of the stimuli may have been threatening. Hence Study 2 produced a validated stimulus set of compassionate and critical expressions to be used in further studies of this thesis. Studies 3 and 4 found that individual differences in self-criticism (and to a lesser degree anxiety) influence the way in which compassionate expressions are attended to. The key findings were that high self-critics showed diminished attention to compassionate faces (Study 3) however, when given critical imagery (Study 4), high self-critics showed enhanced attention to compassionate faces. This reversal in attentional processing may be due to finding the compassionate faces threatening or alternatively could reflect participant's attempts to reduce distress through seeking affiliation. Self-criticism is a transdiagnostic factor characterising a variety of mental health difficulties and has been shown to interfere with treatment effectiveness (Rector, Bagby, Segal, Joffe, & Levitt, 2000). This thesis has shown that self-criticism is associated with difficulties in attentional processing of compassionate stimuli. This has clinical implications as this processing difficulty may result in, the maintenance of self-criticism, affective disorders and difficulties in interpersonal relationships including the therapeutic relationship. Compassion has recently become the focus of therapeutic interventions as a treatment for self-criticism (Gilbert, 2005, 2007, 2009; Gilbert & Procter, 2006), hence if self-critics have difficulties processing compassion, this has important implications for therapeutic interventions.