No abstract

Two experiments addressed whether response latency in a trial of the lexical decision task is independent of the lexical status of the item presented in the previous trial. In Exp. 1, it was found that both word and nonword responses were significantly slower when the previous trial had involved a nonword than when it had involved a word. In Exp. 2, which employed a different list composition, it was found that responses to nonwords and pseudohomophones were significantly slower when the previous trial had involved a nonword or a pseudohomophone than when it had involved a word. However, responses to words were not influenced by the nature of the previous trial. We concluded that sequential dependencies exist across consecutive trials in the lexical decision task even when there is no semantic, morphological, phonological, or orthographic relationship between the items presented during those trials.

Three experiments were designed to investigate whether the characteristic function relating response time to stimulus orientation reflects the observer imagining the rotation of the stimulus to upright (the "image rotation" hypothesis) or rotation of an internal reference frame in response to the misoriented stimulus (the "frame rotation" hypothesis). Identification times in response to misoriented words were measured in Experiment 1, whereas in Experiments 2 and 3, lexical decision times in response to misoriented letter strings were measured. Trials occurred in blocks; words within a block were presented at the same orientation. It was argued that this mode of presentation would facilitate the use of a frame rotation strategy by allowing for a gradual readjustment of an internal reference frame. The characteristic "mental rotation" function was observed in all three experiments. However, the data indicated that observers continued to imagine the rotation of the word to upright in each trial; there was no evidence of readjustment of an internal reference frame. An additional finding of interest occurred in Experiment 1, in which observers identified the same set of misoriented words across two sessions. The identification times were faster, and the slope of the mental rotation function was lower, in the second session. These results are discussed as in relation to the image rotation hypothesis of mental rotation and to "instance-based skill acquisition" (Masson, 1986) in word recognition.In the present paper, we examine an issue raised by Koriat and Norman (1984) in the title of their paper" What is rotated in mental rotation?" As an example of research that is usually interpreted as indicating' 'mental rotation," Cooper and Shepard (1973) reported that the time to decide whether an alphanumeric character was in its normal or mirror-image version increased monotonically as the angular deviation from upright increased to 180 0 • Furthermore, this monotonic increase persisted when observers were cued to stimulus orientation prior to each trial. Cooper and Shepard proposed that subjects mentally rotated some internal representation of the alphanumeric to its normal, upright position prior to making a decision about the version of the stimulus. This "normalization" process has been interpreted as supportive of a general class of template models of form perception which Preparation of this report was supported by NASA Cooperative Agreement NCC 2-327 to San Jose State University, Kevin Jordan, Project Director. We would like to thank Pierre Jolicoeur, Asher Koriat, Lester Krueger, and Roger Shepard for many helpful comments on earlier versions of this manuscript. In particular, Pierre Jolicoeur and Asher Koriat suggested the random presentation conditions used in Experiments 2 and 3. Additional thanks go to Susanne Delzell, Kimberly Jobe, Fidel Lam, and Beverly Sanford for their assistance with data collection, John Empey for his technical assistance, and especially Guy Woffindin for programming Experiments 2 and 3. ...

for their insightful, helpful comments on previous versions of this article. We thank Kimberly Jobe, Beverly Sanford, Kelly Smith, and Scott Yettman for their assistance with data collection.

Two lexical decision experiments, using words that were selected and closely matched on several criteria associated with lexical access provide evidence of facilitatory effects of orthographic neighborhood size and no significant evidence of inhibitory effects of orthographic neighborhood frequency on lexical access. The words used in Experiment 1 had few neighbors that were higher in frequency. In Experiment 2, the words employed had several neighbors that were higher in frequency. Both experiments showed that words possessing few neighbors evoked slower responses than those possessing many neighbors. Also, in both experiments, neighborhood size effects occurred even though words from large neighborhoods had more potentially interfering higher-frequency neighbors than words from small neighborhoods.