Fixation positions after skipping saccades: A single space makes a large difference

Abstract

During reading, saccadic eye movements are generated to shift words into the center of the visual field for lexical processing. Recently, Krügel and Engbert (Vision Research 50:1532–1539, 2010) demonstrated that within-word fixation positions are largely shifted to the left after skipped words. However, explanations of the origin of this effect cannot be drawn from normal reading data alone. Here we show that the large effect of skipped words on the distribution of within-word fixation positions is primarily based on rather subtle differences in the low-level visual information acquired before saccades. Using arrangements of “x” letter strings, we reproduced the effect of skipped character strings in a highly controlled single-saccade task. Our results demonstrate that the effect of skipped words in reading is the signature of a general visuomotor phenomenon. Moreover, our findings extend beyond the scope of the widely accepted range-error model, which posits that within-word fixation positions in reading depend solely on the distances of target words. We expect that our results will provide critical boundary conditions for the development of visuomotor models of saccade planning during reading.Electronic supplementary materialThe online version of this article (doi:10.3758/s13414-012-0365-1) contains supplementary material, which is available to authorized users.

Linguistic processes do not beat visuo-motor constraints, but they modulate where the eyes move regardless of word boundaries: Evidence against top-down word-based eye-movement control during reading

“…However, this was unlikely the case because saccades’ landing positions were also strongly influenced by the length of peripheral words. Note in addition, that several previous studies showed that the slope of the linear relationship between saccades’ launch sites and within-word landing sites is not invariant, but rather depends on the peripheral visual configuration [39, 127, 128]. Accordingly, but in contradiction with McConkie et al’s [22] original findings, we found that the effect of launch-site distance on (within-word) landing positions became stronger with increasing word length.…”

A model of saccadic landing positions in reading under the influence of sensory noise

“…Thus, effectively, we propose that in word-skipping saccades the words N + 1 and N + 2 are treated as a perceptual two-word target region for saccade planning. This is in line with previous theoretical explanations of the left-shift of landing distributions in word skipping (Drieghe et al, 2008;Krügel et al, 2012;Radach, 1996;Radach & Kempe, 1993;Radach & McConkie, 1998). However, in contrast to Radach (1996) and Radach and McConkie (1998), we do not claim that the grouping of words in word skipping reflects an occasionally top-down controlled modification of the target location for the sake of further processing of the skipped word.…”

“…Moreover, the standard deviations of the distributions of landing positions in word-skipping saccades markedly increased with increasing launch-site distances, whereas the standard deviations of the landing distributions in one-step saccades only slightly increased with longer target-word distances. It is important to note that this effect of skipping saccades on landing positions was recently qualitatively replicated for the skipping of meaningless letter-strings in a singlesaccade experiment (Krügel et al, 2012). This result was surprising and counterintuitive, since left-shifted landing positions were detrimental for the task employed in the experimental paradigm.…”

“…This happens regardless of whether or not the skipped letter string carries relevant semantic information (Krügel et al, 2012), suggesting that only low-level visual properties are exploited by the visuo-motor system during saccade planning. To capture this general left-shift after skipping saccades compared to one-step saccades, we assume that the blank space between word N and word N + 1 defines the beginning of the target region for the next progressive inter-word saccade, regardless of saccade type (i.e., for onestep as well as for skipping saccades).…”

Modulation of oculomotor control during reading of mirrored and inverted texts

“…Second, Krügel and Engbert [20] demonstrated that saccade type (i.e. word skipping) could influence the saccade landing positions during reading [see also 22,37]. These findings challenged the range-error model in explaining observed saccadic landing positions during reading.…”