In recognition testing, people are presented with previously studied material mixed with unstudied material. A multiple-choice exam is an example of recognition testing. The student studies the material and then has to recognize the correct answer from among the choices provided. In relearning, retention is measured in terms of how much faster one learns material that was learned but then forgotten. People often retain or remember more information than they recall, which leads to this faster relearning. Retaking a course is an example of relearning. Typically, the student learns the material faster and with fewer errors the second time around.
Anything present at the time learning occurred can serve as contextual cues, including smells, sounds, sights, and the emotional state of the learner. For example, people more easily remember an event that took place in a room if they go back to that room. It is also easier to remember material when the emotional learning context matches the emotional retrieval context. Research suggests this context-dependent effect occurs not just for explicit memory but for implicit memory, as well.Another robust explicit memory phenomenon is the serial position effect (also called the primacy-recency effect), in which there is a tendency to remember more information from the beginning and end of an event than from the middle. This was first discovered by German philosopher Hermann Ebbinghaus in 1885 while studying human memory for word lists. The effect applies to explicit memories as diverse as memory for operas attended over the course of decades and gymnastic floor routines. The serial position effect reflects the impact of two factors—proactive interference and retroactive interference. In proactive interference, there is a tendency of earlier learning to impair memory for information acquired later. In retroactive interference, there is a tendency of later learning to impair memory of information learned earlier. For example, suppose a person were asked to memorize the words hat, chair, vase, frame, bowl, window, candy, stair, and cup. Words that come before bowl can disrupt encoding of that word, as can words that come after. Words in the beginning of the list are better remembered because they have less proactive interference (fewer words precede them). Similarly, words at the end of the list are better remembered because they have less retroactive interference (fewer words follow them). Words in the middle are poorly remembered because they suffer from both proactive and retroactive interference.