Mindless reading: eye-movement characteristics are similar in scanning letter strings and reading texts.

The purpose of the present study was to compare the oculomotor behavior of readers scanning meaningful and meaningless materials. Four conditions were used--a normal-text-reading control condition, and three experimental conditions in which the amount of linguistic processing was reduced, either by presenting the subjects with repeated letter strings or by asking the subjects to search for a target letter in texts or letter strings. The results show that global eye-movement characteristics (such as saccade size and fixation duration), as well as local characteristics (such as word-skipping rate, landing site, refixation probability, and refixation position), are very similar in the four conditions. The finding that the eyes are capable of generating an autonomous oculomotor scanning strategy in the absence of any linguistic information to process argues in favor of the idea that such predetermined oculomotor strategies might be an important determinant of eye movements in reading.

Loss of vision during the retinal stabilization of letters.

Upper- and lower-case letters of the alphabet were stabilized until loss of vision occurred. Loss of straight-line visibility was the most frequently reported perceptual event. Occasionally, features of letters separated spatially before their loss of visibility. In both instances, loss of visibility often resulted in the perception of a less complex letter. Confidence ratings for each loss of letter visibility indicated that participants were quite certain about perceived fragmentations. In a control experiment, participants were asked to guess how letters would fragment during stabilization. Again, loss of line visibility was the most frequently reported event. However, spatial separation of features was rarely predicted and complex letters were not predicted to fragment into simpler letter forms. Furthermore, the confidence in predicted fragmentation was quite low. These results are consistent with the view that losses of visibility during retinal stabilization constitute a distinct perceptual experience. Fragmentations appear to be determined by the availability of less complex letter forms and by the loss of subletter information, consisting of letter features and information specifying spatial configurations.

Seeing morphemes: loss of visibility during the retinal stabilization of compound and pseudocompound words.

When stabilized, a retinal image fades from vision. Earlier studies suggested that knowledge constrains the loss of vision, as disappearing images fragment into familiar subpatterns. Effects of image stabilization on word perception were used in the current study to examine effects of morphemic knowledge on stimulus fragmentations. Bimorphemic compound words (in which beginning and ending trigrams formed morphemic subword units) and monomorphemic pseudo-compound words (with a similar trigram structure) were stabilized. Stimulus fragmentations generally resulted in the visibility of lexically nondistinct strings of letters. However, internal morpheme boundaries also affected the loss of vision when compound words were stabilized. Two follow-up experiments indicated that morpheme-related loss of vision was neither the result of differential forgetting rates nor of guessing bias.

Attention demands during reading and the occurrence of brief (express) fixations.

Eye movements were recorded while subjects read passages of text repeatedly (Experiment 1) and while normal text and strings of homogeneous letters were fixated (Experiment 2). Text repetition decreased fixation durations and increased saccade size, presumably because it decreased attention demands. Irrespective of repetition, however, no distinct distribution of brief (express) fixations emerged. In Experiment 2, fixation durations were shorter and saccades were larger when strings of homogeneous letters were "read," indicating that this condition decreased attention demands. Again, however, no distinct distribution of express fixations emerged. These findings pose problems for the view that attentional processes determine the occurrence of brief (express) fixation durations in reading. Supplementary analyses of Experiments 1 and 2 suggested that visuospatial processing affected fixation durations, irrespective of linguistic processing demands.

Saccade programming during short duration fixations: an examination of copy typing, letter detection, and reading.

Three experiments examined saccade programming during short duration fixations between 50 ms and 150 ms. In experiment 1, subjects copy typed text, in experiment 2, subjects read and executed a letter detection task, and in experiment 3, subjects read for comprehension only. Fixation duration had no effect on the size of the departing saccade in the copy typing task; however, saccades leaving short duration fixations were larger than saccades leaving all other fixation durations in the letter detection task and smaller than saccades leaving long fixation durations in the standard reading task. Within Morrison's (1984) model, these results imply, first, that consecutive shifts of attention during a fixation can take different directions and, second, that successive shifts of attention during a fixation support different purposes. Within Fischer's (1986, in press) model, the results imply that the engagement/disengagement of attention and saccade programming do not constitute independent events.

Spatial and temporal frequency in figure-ground organization.

Figure-ground organization of an ambiguous pattern can be manipulated by the spatial and temporal frequency content of the two regions of the pattern. Controlling for space-averaged luminance and perceived contrast, we tested patterns in which the two regions of the ambiguous pattern contained sine-wave gratings of 8, 4, 1, or 0.5 cycles per degree (cpd) undergoing on:off flicker at the rates of 0, 3.75, 7.5, or 15 Hz. For a full set of combinations of temporal frequency differences, with each spatial frequency the higher temporal frequency was seen as background for more of the viewing time. For two spatial frequency combinations, 1 and 4 cpd, and 1 and 8 cpd, tested under each of the four temporal frequencies, the lower spatial frequency region was seen as the background for more of the viewing time. When the effects of spatial and temporal frequency were set in opposition, neither was predominant in determining perceptual organization. It is suggested that figure-ground organization may parallel the sustained-transient response characteristics of the visual system.