Navon Global-Local Task

The Navon task, introduced by Navon (1977), is the classic paradigm for studying global and local processing of hierarchical visual stimuli. On each trial participants see a large letter (the global level) constructed from many smaller letters (the local level). In separate blocks they are asked to respond to the large letter while ignoring the small ones (global block), and then to respond to the small letters while ignoring the large one (local block).

The stimuli are the letters H and S. There are four types of trial:

Two main findings emerge. Global precedence (Navon, 1977): responses in the global block are faster than in the local block — people identify large letters faster than small ones. Asymmetric interference: on incongruent trials the irrelevant global letter slows local judgments more than the irrelevant local letters slow global judgments — global information intrudes on local processing more than the reverse.

Response keys are ← (Left Arrow) for H and → (Right Arrow) for S in both blocks; only the attended level changes between blocks. Practice trials at the start of each block give participants feedback on each response.