As well as physical attraction, many people are drawn to someone who shares the same interests. Relationship psychotherapist Paula Hall explores why we fall in love with some people and not with others.
In some relationships, arguments always seem one sided - with one partner making all the noise as the other quietly calms the storm. It's possible they both have a problem expressing their feelings, but together they're able to reassure each other that emotions are being managed. Different couples will experience it in different ways, but that inexplicable feeling of wholeness you have when you're together is what Henry Dicks, a guru in relationship psychotherapy, called the 'unconscious fit'.
All of us carry with us a psychological blueprint, holding details about our life experiences and the marks they've left. It contains information we often haven't acknowledged about our fears and anxieties and our coping mechanisms and defences.
Each of us has an unconscious capacity to scan another person's blueprint. The people we're most attracted to are those who have a blueprint that complements our own. We're looking for similarities of experience but, more significantly, we're also looking for differences.
The purpose of this unconscious fit is to find someone who can complement our experiences. That might be someone who's the same as us, but most commonly we're looking for someone from whom we can learn; someone who has developed coping mechanisms that are different from our own.
The ideal partner will be someone who has struggled with similar life issues, but has developed another way of managing it. It seems that our other half is often our best chance of becoming psychologically whole.
Although no two relationships are ever the same, psychologists have noticed that there are some common types of unconscious fit. Do you recognise any of these?
Parent and child - this type of couple often has shared issues with dependency and trust. One partner copes with those issues by behaving in a childlike way. Their hidden belief is that if they remain insecure, dependent and needy their partner will look after them. Their partner takes on the role of parent and by doing so is able to deny their own needs for dependency as they're acted out by the other.
Master and slave - this couple has a problem with authority and control. One partner may feel very insecure if they're ever subordinate, so they're bossy and take charge of every household circumstance. Their partner, who fears responsibility, dutifully toes the line while smugly comparing what they describe as their laid-back attitude to their partner's control-freak attitude.
Distancer and pursuer - both partners are afraid of intimacy but have found their perfect match. The unspoken agreement is that one of them will keep chasing and nagging the other one for more intimacy while the other runs away. Occasionally the chase will swap round.
Idol and worshipper - when one partner insists on putting the other on a pedestal, this often indicates an issue with competition. To avoid any form of comparison, both partners unconsciously agree to play this game.
There are two other common types of fit based on finding a partner who has a similar problem and a similar way of coping.
Babes in the wood - you may have seen this couple around. They look alike and often wear matching sweaters. They share the same interests and, more importantly, they dislike the same things. They keep anything bad out of their perfect relationship by joining forces against the big, bad world outside.
Cat and dog - on the surface these partners look as though they should never have even met. They argue incessantly over anything. They both avoid intimacy by living in a war zone.
You may see elements of your relationship in all of these types. As we progress through our relationships, it's not uncommon to slip into a certain pattern of behaviour. For example, in a time of illness and vulnerability you may act out the parent and child model, while many couples become like babes in the wood following the birth of a child.
All fits serve a psychological purpose designed to protect ourselves from discomfort. Most couples aren't aware of their fit until something happens to change it. We all grow and mature, our needs change and our relationships need to adapt to those changes.
Problems may start when one or both partners feell they are no longer able to communicate their feelings and alter patterns of behaviour that are now outdated. If you think that may be happening in your relationship, see When you first met.
If this article has raised some difficult issues for you then try talking it through with a partner or trusted friend. Alternatively you may want to consider counselling. If you're not sure whether this would be right for you, or if you want to find out more about it, have a look at our article Do you need counselling?