**7. Overview of dyadic relationships**

*Relationship quality* is a multifactorial construct and can be broken down into overall satisfaction, commitment, closeness or intimacy, passion, trust and love [150]. Spanier [151], p. 290, defined relationship quality as 'a subjective evaluation of a married couple's relationship with the range of evaluations constituting a continuum reflecting numerous characteristics of marital interaction and marital functioning'. In the context of marriage, relationship quality encompasses adjustment, satisfaction, integration and happiness and can be seen in terms of its functionality and how the partners are affected by its functioning [151].

*Relationship satisfaction* is one of the key components of relationship quality. It has been defined in the context of interdependence theory [152, 153], which sees the interaction between partners, dependence and satisfaction as the core elements in close intimate relationships [154]. The dyadic *interaction* consists of rewards (i.e. pleasure, enjoyment, fulfilment) as well as costs (i.e. stress, pain, shame) that each partner may receive in the relationship. The goal is to minimise costs and maximise rewards [154]. Relationship satisfaction is affected by the level of one partner fulfilling the most significant needs of the other partner [155]. Each individual assesses the gains and benefits in their relationship as well as outputs they give to their partner. Relationship satisfaction is higher when the input-outcome ratio equates with that of the partner, whereas an imbalance in the ratio leads to dissatisfaction with the relationship [154].
