Often a question arises on writers’ forums: ‘How should I use the backstory of a character?’ This goes along with questions about whether or not a backstory should be fully developed or be only partly known by the writer.
Answers range from ‘Yes, have a filing cabinet full of information about your character so that you can bring it out whenever it becomes relevant’ to ‘No, just make it up as you go along.’
It can only be properly answered if it is seen in relation to a different, more fundamental question about fiction: ‘What are you trying to accomplish?’
If you get that clear, suddenly a character becomes something quite different to the usual definition: instead of being a proxy human with a whole history, a kind of ‘proto-person’ with a set of known attributes and credentials, a character becomes a tool for achieving an aim.
With this in mind, we can answer the question about backstory:
Backstory should only be used - or even developed - if it serves a purpose.
Backstory in itself - filing cabinets full of data about a made-up person, ranging from birthday to star sign to preferred type of socks - is utterly pointless and a waste of a writer’s time, unless it is relevant to the task at hand.
What is that task?
Moving the reader from Point A - i.e. not really caring or being engaged with a writer’s message or theme or ideas - to Point B: totally buying those things and being emotionally and even spiritually affected by them.
In giving readers backstory, a writer may think he or she is laying the foundation for something significant later, or hoping that a certain level of detail is going to draw the reader in. But readers are not drawn in by details unless those details are strictly relevant to other things in the story, like what is going to happen next, or what is really going on, or what is the right or wrong thing at a particular point. The specific preference of a character for one type of sock may be crucial if that type of sock was used to strangle someone in the murder at the heart of a tale - otherwise it is utterly superfluous and does absolutely nothing to advance the purpose of the writer.
Research for your novel is important. But knowledge about characters does not and should not be given to readers unless it forwards their movement towards fulfilment - i.e. their full and satisfied apprehension of the intentions of the author.
It is up to the author to decide if information is worth keeping in or if it should be cut entirely as a distraction. Ask whether readers will want to know the information, or, more powerfully, ask whether or not more information about a character increases or decreases their pulling power. Sometimes, too much information, in making a character seem well-rounded, detracts from that character’s ability to attract attention. It was not for nothing that Clint Eastwood’s character in the spaghetti westerns of the 1970s was called ‘The Man with No Name’.