Von Restorff Effect

The Von Restorff effect, also known as the "isolation effect", predicts that when multiple homogeneous stimuli are presented, the stimulus that differs from the rest is more likely to be remembered.

The theory was coined by German psychiatrist and pediatrician Hedwig von Restorff (1906–1962), who, in her 1933 study, found that when participants were presented with a list of categorically similar items with one distinctive, isolated item on the list, memory for the item was improved.