Decisions about identity and orientation of rotated letters and digits

In three experiments, human observers made timed decisions about alphanumeric characters, displayed singly in different orientations and versions (normal vs. backward). Latency to identify the characters was longer for backward than for normal versions, regardless of angular orientation and even under conditions in which latency was independent of angular orientation. Subjects also took longer to respond to a target orientation (whatever the character) than to respond to a target character (whatever the orientation). The results suggest that the observer first induces a description of a character that is largely independent of orientation but not of version, although the representation of version is too weak at this stage to permit an overt decision about it. Next, the angular orientation of the character is determined. Finally, the observer might “mentally rotate” the representation to the standard upright, for matching against an internally generated template.