A users mental processing is made slower and less efficient by competing process resulting in a mental conflict and incongruent results. Some interference effects include, Stroop (an irrelevant aspect of a stimulus interferes with a relevant aspect), Garner (an irrelevant variation of a stimulus interferes with a relevant aspect of a stimulus), Proactive (A learned experience interferes with the current stimulus) and Retroactive (The current stimulus inteferes with an existing memory).