Rotated Letters Research Articles

Interaction between perceived and imagined rotation.

In Experiment 1, subjects performed a mental-rotation task in which they were timed as they decided whether rotated letters were normal or backwards. Between presentations of the letters, they watched a rotating textured disk that induced an aftereffect of rotary movement on the letters. The function relating reaction times to orientation was influenced asymmetrically by the aftereffect, suggesting that perceived movement interacts with imagined movement. Experiment 2 showed that the aftereffect produced a negligible influence on perceived orientation, suggesting that the influence of the aftereffect on mental rotation was not caused by changes in the perceived orientations of the letters. Detailed analysis of the mental-rotation functions suggested that the aftereffect may sometimes have induced subjects to rotate letters through the larger rather than the smaller angle back to the upright where the aftereffect was in the appropriate direction.

Familiarity effects in a same-different task with simultaneous and successive presentation

To assess conflicting results of prior studies concerned with the effects of familiarity and task conditions on the performance of visual matching tasks, six groups of independent observers (N = 8) each received three blocked trials of 12 “same” and 12 “different” pairs (randomly ordered) of letters, rotated letters, or nonsense forms presented simultaneously or successively in a tachistoscope. Each observer was asked to judge whether the elements of each pair were “same” or “different.” Analysis of the RTs showed that judgments of the nonsense forms were slower than the equally fast responses to the letters and rotated letters. An interaction between presentation mode and type of stimulus pair indicated that judgments of “same” pairs were somewhat faster with successive than with simultaneous presentation, but “different” pairs were judged equally fast under both modes. The results are related to earlier studies of familiarity, but emphasis is placed on a facilitation hypothesis based on meaningfulness.

The effects of verbal meaning and response categorisation on the fragmentation of steadily fixated patterns.

Studies of steady visual stimulation have suggested that the subjective meaning of a stimulus may determine the form and degree of its perceptual fragmentation. This was tested for steady fixation by presenting a letter of the alphabet ("L") in a sequence of other letters which were either normally oriented or inverted. No evidence was found for greater stability in the former case. An investigation of the categorisation of subjective disappearances showed that, although the stability of pattern components was not determined by reporting these singly or in conjunction, the disappearances of the whole pattern were significantly increased by reporting only these as opposed to reporting disappearances of each component. Response to stimulated subjective disappearances also showed that the effect was due to the nature rather than the number of response categories. In the final experiment all subjects fixated a rotated letter, after half had received pretraining in the recognition of rotated letters. No effects of the pretraining were apparent, for either level of response categorisation, and it was concluded that the processes underlying subjective disappearances in steady fixation are not modified by the meaningfulness of a stimulus. The involvement of central processes was, however, indicated by the effects of response categorisation and the influence of simulated disappearances on pattern stability in a trial subsequent to their presentation.

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.

Locus of rotation effects in recognition

Test-letter orientation has different effects on positive- and negative-recognition reaction time; furthermore, when two test letters are presented simultaneously, the effect of nontarget test orientation differs for positive and negative responses. Orientation is seen to affect the output but not the duration of the comparison stage; the continuously variable comparison output then influences the duration of the decision stage. These data show that the processing of rotated letters in recognition does not involve mental rotation.