Serial Position Effect: Why Order Matters in Optimization

June 9, 2016


You put tons of time into creating your product(s), experimenting with acquisition channels, honing your messaging – and here I am, about to tell you about how consumers are often swayed by such a subtle thing as the order in which you present your products.


It’s a funny thing, human behavior.


Often, small nudges can produce significant changes in how we act. The Serial Position Effect is one such behavioral nudge. It has interesting implications for memory, preference, and behavior – and of course for designing and optimizing your website.


Serial Position Effect and How It Affects Memory


Serial position effect is the tendency of a person to remember the first and last items in a series best and the middle items worst. It’s made of two parts:

  • Primacy effect

  • Recency effect

Primacy and Recency Explained


Primacy: Things that happen first are typically the most important because they influence what comes next.


The theory behind primacy effect is that there is a relatively small amount of processing effort expended in rehearsing the item by itself. So, basically, when you process the 9th item on a list, you’re also processing the previous 8, where the first one is by itself. This results in greater cognitive fluency and therefore greater recall.


Recency: Things that just happened are relevant because they are the most accurate representation of “now.”


The theory behind recency effect is that items at the end of a sequence are easier remember because of their preservation in our working memory (the part of our short-term memory that processes conscious and immediate perceptual information). Our working memory only holds ephemeral information. It acts as a buffer for new information while it processes it into other, longer-term memory systems.


All that stuff in the middle? That’s likely to be forgotten. Even if people read everything, the stuff in the middle would be the most likely to be forgotten.


The effect Primacy and Recency have on recall is powerful and well studied. It’s not a new concept, at all. Apparently Hermann Ebbinghaus (1850-1909) originally coined the term ‘serial position effect’ after conducting a number of memory studies on himself.

Then this study from 1962, where researchers analyzed free recall of word lists ranging from 10 to 40 words, supported the effect. Here’s a chart of the results:



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