The Von Restorff Effect (named after the psychiatrist who first studied it, Hedwig von Restorff) describes our tendency to remember things that stand out or, in other words, that we are more likely to remember the unusual. For example, in a list of words that are all written out in the same way (same size, colour, font, etc.) except for one that is notably different (for instance the only one that is in red), we will obviously notice this one and remember it more clearly. This principle can be applied to all manner of things: words, products, images, communication messages, an unexpected happening during a course of standard events, etc.
This effect manifests itself due to the contrast evoked between one element and the others which causes our brains to wake up and pay more attention, meaning that this different element will not only be noticed in the present moment but stick in our brains for longer. Von Restorff showed in her studies how our eyes and brains are constantly on the lookout for things that disrupt the norm, meaning we are constantly waiting to have our attention seized by anything out of the ordinary. This principle is also known as the Isolation, Prominence or Distinction effect as it is the very fact of being presented with an element that is at odds with everything else.
This principle is often used in the world of marketing and advertising to engage a target audience and is particularly effective in this age of multiple communication platforms. An advert that stands out from the rest (be that through its tone, visuals used, unique message, or other mode of distinction) will be noticed and remembered more clearly than those that are more similar to each other.