The human eye is not a recording device, like a camera, but is more like an intelligent search engine that actively sorts through the visual information that is continuously streaming toward it. Visual perception is, in fact, the act of visual selection.

Through a process of scanning and sorting, the eye filters visual information, ignoring  “sensory-spam” in much the same way that you rapidly decide which emails in your inbox to look at and which to delete. This process operates on a pre-conscious level, driven by our unconscious emotions.

It does this because our conscious mind has very little workspace for focusing attention. A long time ago a phone company conducted research determining that the average person could hold only seven bits of information in their working memory at once—which is why phone numbers were originally seven digits long.

Ad researchers have longed probed the contents of working memory—usually by interrogating the thoughts and feelings of consumers immediately after exposure to an ad.  This is the purpose of a communications check.

Another, non-verbal approach is to use recognition, not recall, to retrieve the contents of short-term memory. Still photographs, taken from the ad itself, are shown in randomized order and respondents are asked to identify the ones they remember.

The results from this memory test are then plotted to form of a memory map of a commercial. In this kind of graph, the pictures are plotted in the order in which they actually appear in the commercial, and the height of each picture on the Y-axis shows the percentage of the audience that remembers the image only a short time after viewing the ad.

Typically, there will be rhythmic pattern like a sine wave in the memory map. This is because the mind is automatically chunking information together as it processes it into perception, like forming paragraphs in a piece of writing.

The chunking is based on the psychological process known as the “attentional blink.”  When the mind focuses attention on a meaningful image in the image stream, it pushes adjacent images, those that came before or after, out of the limited window of consciousness and is unable to record them in working memory—a metaphorical blink that lasts for about half a second.

The images that crest on the peaks of the memory waves flowing through advertising, therefore, are those that the search engine of the unconscious mind of the audience has decided are the most important. These are the short-term memories created by a TV Ad.