Why is lower case better? Some data from a search task

Words set in capital letters are less legible than in lower case when reading text, searching for newspaper headlines, or finding a name on a map. The difference is usually attributed to the distinctive shape of lower case words, but lower case setting also emphasises capital letters at the start of sentences and for proper names. In the experiment reported here people searched for names on a map-like display. Names set entirely in lower case (eg, southampton) took significantly longer to find than those set in small capitals with a large initial capital (eg, Southampton) and so, for this task, emphasis given to the initial letter is clearly more important than word shape. This calls into doubt the world shape explanation in other contexts.