The event is non-meaningful so the brain doesn’t record/file every detail about the experience; this of course would be different per individual.
Shocking the individual or tying an emotional response to the event may make it meaningful but probably won’t translate to the brain on its importance.
We are creatures of habit and instinct and if a human was to be trained on the importance of letter/pattern order recognition from an early age, they would most be more effective than a person who has ruled out the importance of such an experience or event.