Whatever you do now, do not read any further than this sentence.
Be honest. Did you find it easy to obey this instruction or are you still reading these words?
If you did ignore it and continued, then congratulations! You are perfectly normal.
As human beings, we have an insatiable desire to figure out what comes next. In other words, we always want to know how the story ends. When we feel a part of the puzzle is missing, this creates what is known as a ‘curiosity gap.’
Think of it as the space between what we know and what we want or even need to know. This technique is so effective because the brain rewards itself for working things out. By incentivising us to problem solve, this serves a clear evolutionary purpose. It’s why those annoying ‘clickbait’ articles are so effective and why every episode of your favourite TV show ends on a ‘cliffhanger.’
This cunning plot device was invented to ensure the audience would return to see how the dilemma was resolved. It dates as far back as the famous medieval Arabic text One Thousand and One Nights where the character Scheherazade narrates a series of stories to King Shahryār. She does this for 1,001 nights, with each night ending on a cliffhanger in order to save herself from execution.
The technique gained broad popularity in 19th Century Victorian England with the writer Charles Dickens. His novels pioneered the serialised format as a money making device (Dickens was able to make more revenue from selling his books as individual parts than as a whole). To keep his readers hooked, each new chapter would end with a key issue needing to be resolved.
Interestingly, the term itself seems to have originated later in 1873 with the writer Thomas Hardy. At the end of one of his serialised accounts, the protagonist, Henry Knight, is left hanging off a cliff.
As a storyteller you can exploit this tool to great effect to build tension in your narrative. Just be sure to deploy it in the right set of circumstances to avoid it coming off as forced.