Negative priming is a concept in cognitive attention and memory research that refers to the decrease in response speed and the increase in errors when naming or recognizing objects that have been previously ignored. Early research on this cognitive phenomenon was first introduced by John Dalrymple-Alford with the term negative priming being later coined by Steven Tipper. Research suggests there are two types of cognitive processes involved with negative priming. The first is inhibition because previously ignored stimuli is still cognitively represented as being 'blocked' and therefore the brain takes longer to recognize it. The second cognitive process involved is faulty memory retrieval because the ignored stimuli is still associated with the memory of how to act when encountering it- the memory being to ignore it.
For example, you are a teacher and always use a blue marker to grade papers. Every time you grade papers you reach into the marker box and out of 8 different colors you select the blue marker. In research terms the blue marker is the target stimulus (the one that you want to select) while all of the other non-blue markers are 'distractors' that your brain ignores in order to be able to correctly select the blue marker. One day, you need to use a green marker. Because you typically choose the blue marker there is a brief delay in selecting the green marker. This change in stimuli from being a distractor (and previously ignored) to a target stimulus causes the delay that is known as negative priming.