Specification: Factors affecting attraction in romantic relationships: filter theory, including social demography, similarity in attitudes and complementarity. 

Filter Theory 

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 called 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 and religion. These factors are important because people are more likely to build relationships with people who are geographically close, and with whom they are meeting frequently, as this gives them a greater chance to find out more about one another given the greater accessibility. People 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 the 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 and come to an end. 

Although similarities are crucial at the early stages of relationships, Kerckhoff and Davis (1962) suggest 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. Winch (1957) supports this view and found that similarity of interests, attitudes and personality traits were very important for couples at the beginning of relationships, and complementarity of needs had more impact on long-term relationships. Complementarity is an appealing notion for partners as it appears that the coming together of two halves created a whole in the union of their relationship. 

Research Examining Filter Theory: Kerckhoff and Davis (1962) 

Aim: A longitudinal study to test the Filter Theory of relationships. 

Methods: 94 participant couples who were dating from Duke University in America answered two questionnaires. One assessed shared values and attitudes and the other was designed to ascertain to what extent the individual needed complementarity in a relationship. Seven months later, the couple completed a third questionnaire asking them to rate closeness to their partner from the beginning of the study to the present day. 

Results: Initial analysis revealed that only similarity between partners appeared to be related to ratings of closeness towards a partner. However, upon analysing the results of the couples separately according to those who had been in a short-term relationship (>18 months) compared to those who had been in a long-term relationship (<18 months), other differences appeared in the findings. Couples in short-term relationships rated shared values and attitudes as the most important factor in feeling close to their romantic partner. On the other hand, for couples in long-term relationships, it was only complementarity which was indicative of closeness in their partnership. 

Conclusion: Kerckhoff and Davis’s (1962) study provides research support for the filter theory of romantic relationships with evidence that complementarity, as the third ‘filter’, is the most important in relationships over 18-months long in duration and before that time, similarity of attitudes is most important. 

Evaluating Filter Theory

One strength of Filter Theory is that it is supported by research studies. Gruber-Baldini et al. (1995) carried out a longitudinal study across 7-year intervals from 1956-1984 with 169 couples. They 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 relationship. In addition, positive spousal correlations were found for flexibility of attitude for those partners who had been together for longer than 21 years. This demonstrates the importance of sociodemographic factors, such as age and education, supporting the idea that people are more likely to meet and build relationships with people who are geographically close and share similarities in their background. 

Another weakness of Filter Theory is that it may be less relevant today than when it was first proposed. Sociodemographic factors, in particular, may not play as big a role in the development of relationships today, 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. This suggests that the Filter Theory lacks temporal validity and needs to be updated to consider more modern methods of dating.  

One issue with Filter Theory is that subsequent research has 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 months to establish similarity of attitudes and complementarity, 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, such as the type of relationship, play a significant role in the initiation and further development of romantic relationships. 

Extension Evaluation: Issues & Debates 

Most research supporting the Filter Theory uses participants from individualist, Western cultures. Individualist cultures value free will with regard to relationship choice 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 cultural bias, as it assumes that the rules of partner choice in Western cultures apply to relationships universally.

Basing the explanation of such a complex phenomenon, such 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 longterm relationships. This suggests that a holistic approach to studying romantic relationships may be better suited to explaining the complexity of relationship maintenance. 

Possible Exam Questions 

1. Identify which two of the following statements are important factors relating to attraction in romantic relationships, according to the Filter Theory. (2 marks) 

a. Similarity of attitudes 

b. Receiving compliments 

c. Economic profit and loss 

d. Reciprocal self-disclosure 

e. Social demography 

2. Define complementarity, in relation to romantic relationships. (2 marks) 

3. Identify which of the statements below relates to each of the key concepts from the Filter Theory – social demography, similarity of attitudes and complementarity. (3 marks) 

A. Sharing the same core beliefs and values as a partner, such as views on career or the importance of having a family. 

B. When each of the partners in a relationship has traits that the other person lacks, thus helping one another’s needs. 

C. Key factors individuals are likely to pay attention to when meeting a person for the first time. 

D. Asking a potential partner about how close they live, what level of education they have achieved and any religious beliefs they hold. 

4. Describe two sociodemographic factors that might play a role at the start of a relationship. (4 marks) 

5. A psychologist decided to investigate the role of similarity of attitudes in short-term relationships, using online questionnaires. 

a. State a suitable operationalised hypothesis for this study. (2 marks) 

b. Suggest which research design would be most suitable for this study and explain two advantages of this design. (6 marks) 

c. Identify one ethical issue the researchers may face in this study and explain how it could be dealt with. (4 marks) 

6. Other than similarity of attitudes, identify and explain one other filter used in determining attraction in romantic relationships, as proposed by the Filter Theory. (3 marks)

7. Sansthita and Rasheed have been dating for two years. They are so similar in their interests, hobbies and attitudes that they believe they are soulmates. Their friends sometimes tease them for finishing each other's sentences. The couple has recently decided to move in together, and when telling her friend about it, Sansthita has commented that she has recently started noticing that it's not only Rasheed’s similarities but their differences as well that make her sure that the relationship will last. ‘Not only do we see eye to eye, but he also completes me in many ways’, Sansthita said to her friend. 

Using your knowledge of the Filter Theory of attraction, explain the development of Sansthita and Rasheed’s relationship. (4 marks) 

8. Explain one strength of Filter Theory. (4 marks) 

9. Describe Filter Theory. Refer to research in your answer. (6 marks) 

10. Outline and evaluate filter theory as an explanation of attraction in romantic relationships. (8 marks) 

11. Discuss Filter Theory. Refer to social demography, similarity of attitudes and complementarity in your response. (16 marks)