Relationships: Filter Theory

When choosing a partner, people start by looking at the options that are available. However, not everyone who is available will be equally attractive, so people usually apply some criteria to narrow down the ‘pool of availabilities’ to make sure they choose the right person.

Filter Theory Explained

Kerckhoff and Davis (1962) studied student couples (mainly in short-term relationships of fewer than 18 months) and discovered several important criteria people use to choose a partner. They call these criteria ‘filters’, as they help people to sift through all potential partners to choose the right one.

According to this theory, there are several levels of filters that people apply. The first level is that of sociodemographic characteristics, such as physical proximity, level of education, social class, religion and other important factors people are likely to pay attention to when we are meeting a person for the first time. These factors are important, because people are more likely to build relationships with people who are geographically close, and whom they are meeting frequently, as this gives them a greater chance to find out more about one another.  People also find similarities in education, social class and religious beliefs attractive, as this gives them assurance that relationships are more likely to move forward.

This then leads to the second level of filters that relates to similarity of attitudes. People tend to view others as more attractive if they share the same core beliefs and values, such as views on career and importance of family. Byrne (1997) noted that similarity of attitudes is especially important in earlier stages of relationships, for couples who have been together fewer than 18 months. Presence or absence of similarities is discovered through self-disclosure, which leads to greater feelings of intimacy in a couple. If partners have very little in common, however, relationships rarely develop beyond the first few dates.

If similarities are crucial at the early stages of relationships, it seems that for long-term couples the third filter, complementarity, plays a much more important role. Complementarity refers to each of the partners having some traits that the other partner lacks, and helping each other to fulfil their needs. For example, one partner may enjoy meeting new people and being socially proactive, and the other may enjoy being introduced to people rather than initiating social encounters themselves, and thus these two people would complement one other.

Research Examining Filter Theory

There is some research support for filter theory. For example, Winch (1957) found that similarity of interests, attitudes and personality traits were very important for couples in the beginning of relationships, and complementarity of needs had more impact on long-term relationships. In another study, Newcomb (1961) offered participants free accommodation for a year.  They were assigned a room mate, and he found that a stable friendship developed if roommates had a similar background and similar attitudes to life.

Evaluating Filter Theory

One strength of Filter Theory is that it is supported by research studies. For example, Gruber-Baldini et al. (1995) carried out a longitudinal study of couples aged 21 and found that those who were similar in educational level and age at the start of the relationship were more likely to stay together and have a successful relationships. This demonstrates the importance of sociodemographic factors, such as age and location, supporting the idea that people are more likely to meet and build relationships with people who are geographically close and share similarities in terms of age, education, etc.

The importance of sociodemographic factors, similarity of attitudes and complementarity in developing attraction is something that many people experience in their everyday life, meaning that filter theory has face validity – as people can relate to it with intuitive ‘this makes sense’ understanding. However, sociodemographic factors, in particular, may not play as big a role in the development of relationships nowadays, as  the development of technology, (such as dating websites and apps) greatly affects modern relationships. Compared with 20-30 years ago, people nowadays are more likely to develop relationships with someone who is not in their geographical proximity or from the same culture, making the Filter Theory’s claims less valid.

Some studies have failed to replicate Kerckhoff and Davis’ original findings. Psychologists such as Levenger (1974) claim that this may be due to the difficulty of correlating length of relationships and depth of relationships, and of determining what constitutes short-term and long-term relationships. Kerckhoff and Davis set the cut-off point for short-term relationships at 18 months, assuming that if people have been in relationships longer, it signifies greater commitment. However, this doesn't apply to all heterosexual couples, nor does it describe the experience of homosexual couples or couples from collectivist cultures. Some couples take much longer than 18 month to establish a similarity of attitudes and complimentarity, while others skip sociodemographic filters altogether and feel they are ready to commit to long-term relationships earlier than the 18 month cut-off point. These experiences can't be explained by the Filter Theory, suggesting that other factors (e.g. the type of relationship) play a significant role in the initiation and development of relationships.

Kerckhoff and Davis (1962) have suggested that similarity of social backgrounds, interests, attitudes and complementarity of needs creates attraction. However, some researchers claim that this direction of causality should be reversed. For example, Anderson et al. (2003) argued, from the results of their longitudinal study, that the emotional responses of partners in long-term relationships become more alike over time rather than being similar from the start. Similarly, Davis and Rusbult (2001) found that attitudes in long-term couples become aligned with time, suggesting that similarity of attitudes is an effect of attraction rather than a cause. This contradicts the claims made by the Filter Theory, which claims that people need to have similar attitudes from the start for relationships to develop. 

Issues & Debates: Filter Theory

Most research supporting the Filter Theory uses participants from individualist, Western cultures. Individualist cultures value free choice in relationships, and describe the choice of partners in terms of individual preferences. In these cultures, people may apply the criteria described by the Filter Theory freely and usually without much influence from other people. However, this is not the case in collectivist cultures, where it is common for romantic relationships to be arranged, so partners are not free to apply individual filters to select their future spouse. This means that Filter Theory suffers from culture bias, as it assumes that the rules of partner choice in Western cultures apply to relationships universally.

Kerckhoff and Davis (1962) and Anderson et al. (2003) are looking for causality, where there may only be positive correlation.  It may be that the very act of being together over time sees a couple’s attitudes shift to converge as their image of themselves as the ‘type of couple they would like to be’ develops. So they start with some similarity of attitudes, but any dissimilar attitudes shift to converge during the relationship.

Basing the explanation of such complex phenomenon as romantic relationships on the application of a series of filters is reductionist and limits the range of real life romantic experiences it can explain. For example, the Filter Theory does not explain why many people stay a long time in abusive relationships despite the lack of complementarity that is theorised as being a factor of long-term relationships. This suggests that a holistic approach to studying romantic relationships may be better suited to explaining the complexity of relationships maintenance.