Why naming takes longer than reading? The special case of Arabic numbers

Since the work of Cattell (1885, 1886), it is known that the time to name a n object (or a color, a geometric figure, a drawing) is longer than the tim e to read the name of that object. This result has been confirmed by many a uthors but the explanation of this phenomenon is still lacking. One good ex planation of the reading-naming time difference is the uncertainty factor. Whereas words are associated with a single response name, pictures are link ed to several names (the so-called "uncertainty hypothesis"). Another good explanation of this difference is the obligatory retrieval of meaning for p ictures but not for words (the so-called "semantic hypothesis"). In the pre sent experiments, subjects had to name Arabic numbers and their correspondi ng written names. By using Arabic numbers and their corresponding written n ames, we contrasted these two hypotheses proposed to explain the reading-na ming time difference. We exploited the fact that Arabic numbers share a ver y important attribute with their corresponding written names: their uncerta inty is null. Indeed, there is only one way to name 5 and Jive. Our results suggest that the main factor responsible for this reading-naming time diff erence is the uncertainty factor, since uncertainty being equal, this diffe rence disappeared completely throughout ten (Experiment 1) and five repeate d sessions (Experiment 2). (C) 1999 Elsevier Science B.V. All rights reserv ed.