Character size, measure, typeface … these are all generally accepted as being factors that influence legibility. Yet the study The uncrowded window of object recognition by New York University neuro-scientists Denis G. Pelli & Katharine A. Tillman published in scientific journal Nature Neuroscience advances the thesis that character spacing is the defining factor for legibility. For this at least a "critical distance" must be exceeded, to allow the brain to read the words and text without effort. When reading a book from a longer distance the letters start to amalgamate and blur. Even though this is rarely the case in daily practice, the research confirms that deciphering text becomes harder when the spacing is maladjusted. By the way the gaps between items are also crucial when viewing everyday objects – if objects are far removed their distance to each other also has to be larger.
The abstract reads:
It is now emerging that vision is usually limited by object spacing rather than size. The visual system recognizes an object by detecting and then combining its features. 'Crowding' occurs when objects are too close together and features from several objects are combined into a jumbled percept. Here, we review the explosion of studies on crowding – in grating discrimination, letter and face recognition, visual search, selective attention, and reading – and find a universal principle, the Bouma law. The critical spacing required to prevent crowding is equal for all objects, although the effect is weaker between dissimilar objects. Furthermore, critical spacing at the cortex is independent of object position, and critical spacing at the visual field is proportional to object distance from fixation. The region where object spacing exceeds critical spacing is the 'uncrowded window'. Observers cannot recognize objects outside of this window and its size limits the speed of reading and search.
Personally I'm still convinced that legibility depends heavily on a combination of well-known typographic parameters, such as typeface, type size, colour, line length, line spacing, medium and also character spacing. Who needs neuro-scientists when one can rely on Bringhurst?
Header image:Willow Lineup 2 © Lars Sundström
Typeface:FF Enzo by Tobias Kvant