serial position effect

The serial position effect is the psychological tendency to remember the first and last items in a list better than those in the middle. The serial position effect is a form of cognitive bias, and it includes both the primacy effect and the recency effect.

The primacy effect is the tendency to remember and place more importance on the items at the beginning of a list. It is thought to be caused by a greater amount of time between the beginning of the list and having to recall the information in which to rehearse the items. This theory is supported by evidence that the primacy effect is lessened when the list is longer or when the list is presented quickly, making it more difficult to rehearse the beginning items.

The recency effect, which is the opposite of the primacy effect, is the tendency to remember the items at the end of a list. This effect is believed to be caused by the more recent items still being stored in short-term, or working, memory, which generally only lasts up to 30 seconds. When presented with a distractor task between presentation of the list and recall, the recency effect lessens, which backs up this explanation.

The serial position effect is used in many forms of advertising and website design. When advertising a product, it is important to place the most important information to the potential customer first and last, as it is most likely to influence a buyer's decision. E-commerce websites position products on a product page carefully as well, showing the products that they would most like to sell near the beginning. In online marketing, links presented at the top of email newsletters or on a search engine results page receive many more clicks. Similarly, links at the beginning and end of a navigation menu on a website will also receive more clicks. Off-line marketing also employs the same principles: Restaurant menus are carefully designed with the serial position effect in mind, and when watching television, consumers are more likely to remember the first and last commercials seen during a commercial break.

German psychologist Hermann Ebbinghaus is credited with creating the term "serial position effect." Ebbinghaus studied memory extensively and discovered the primacy and recency effects, as well as other trends in memory, by conducting experiments in which he measured his own and others' capacity for remembering lists.