Negative priming is an implicit memory effect in which prior exposure to a stimulus unfavorably influences the response to the same stimulus. It falls under the category of priming, which refers to the change in the response towards a stimulus due to a subconscious memory effect. Negative priming describes the slow and error-prone reaction to a stimulus that is previously ignored. For example, a subject may be imagined trying to pick a red pen from a pen holder. The red pen becomes the target of attention, so the subject responds by moving their hand towards it. At this time, they mentally block out all other pens as distractors to aid in closing in on just the red pen. After repeatedly picking the red pen over the others, switching to the blue pen results in a momentary delay picking the pen out (however, there is a decline in the negative priming effect when there is more than one nontarget item that is selected against). The slow reaction due to the change of the distractor stimulus to target stimulus is called the negative priming effect. Negative priming is believed to play a crucial role in attention and memory retrieval processes. When stimuli are perceived through the senses, all the stimuli are encoded within the brain, where each stimulus has its own internal representation. In this perceiving process, some of the stimuli receive more attention than others. Similarly, only some of them are stored in short-term memory. Negative priming is highly related to the selective nature of attention and memory. Broadly, negative priming is also known as the mechanism by which inhibitory control is applied to cognition. This refers only to the inhibition stimuli that can interfere with the current short-term goal of creating a response. The effectiveness of inhibiting the interferences depends on the cognitive control mechanism as a higher number of distractors yields higher load on working memory. Increased load on working memory can in turn result in slower perceptual processing leading to delayed reaction. Therefore, negative priming effect depends on the amount of distractors, effectiveness of the cognitive control mechanism and the availability of the cognitive control resources. Theories and classic models There are a number of theories and models that try to explain the reason behind negative priming. They all try to reason negative priming's role in cognition and justify why it occurs. A few of the well-known models