Theory

Serial Position Effect

Have you ever thought about the maximum number of items a drop-down list or a menu in a GUI can have? Can it be as large as 20? What about the sequence of items in such lists or menus? Is there any logic for sequencing menu-items within a list? Does it affect the interaction time? The design of menus or lists in a GUI is governed by principle of serial position effect.

 

The term serial position effect was coined by Hermann Ebbinghaus which refers to the finding that recall accuracy of an item from a list varies as a function of its position within the list. People tend to recall items at the end of list more reliably (the recency effect). Also the first few items are recalled more frequently than the middle items (the primacy effect).

Refer to the list below and try to remember the items in the list.

1	Amul  Butter
2	Pen  Pencil
3	Diary Milk
4	Orange  Juice
5	Key  Board
6	Drum Sticks
7	Paper Cup

 

It will be observed that you will more reliably recall items in position 1, 2,6 and 7 than those in the position 3,4 and 5.

Applications

We can make use of the recency and primacy effect in sequencing items in a menu of a GUI or a control panel of a product's interface. The more important or more frequently used items or controls should be placed in the beginning or end of the list. Items less frequently used should be placed in the middle of the list. A list of written words may be more easy to recall than a set of colors or symbols.

In case of a list using colors the serial position effect may not be immediately seen. Here recall depends on various properties of color such as brightness, hue and saturation too. Thus a brighter color regardless of its position in the list is more likely to be recalled. This can be used to over-rule the serial position effect whenever the context demands. Thus color can be used as a design element to aid recall.

or example, while designing a tool bar, an important command which cannot be accommodated at the starting or ending of a list, could be placed in middle part with a slightly brighter color, so that it still receives the attention of the user and the user tends to remember it easily and for a longer time.