Unsegmented text delays word identification: Evidence from a survival analysis of fixation durations

Abstract

The present study employed distributional analyses of fixation times to examine the impact of removing spaces between words during reading. Specifically, we presented high and low frequency target words in a normal text condition that contained spaces (e.g., “John decided to sell the table in the garage sale”) and in an unsegmented text condition that contained random numbers instead of spaces (e.g., “John4decided8to5sell9the7table2in3the9garage6sale”). The unsegmented text condition produced larger word frequency effects relative to the normal text condition for the gaze duration and total time measures (for similar findings, see Rayner, Fischer, & Pollatsek, 1998), which indicates that removing spaces can impact the word identification stage of reading. To further examine the effect of spacing on word identification, we used distributional analyses of first-fixation durations to contrast the time course of word frequency effects in the normal versus the unsegmented text conditions. In replication of prior findings (Reingold, Reichle, Glaholt, & Sheridan, 2012; Staub, White, Drieghe, Hollway, & Rayner, 2010), ex-Gaussian fitting revealed that the word frequency variable impacted both the shift and the skew of the distributions, and this pattern of results occurred for both the normal and unsegmented text conditions. In addition, a survival analysis technique revealed a later time course of word frequency effects in the unsegmented relative to the normal condition, such that the earliest discernible influence of word frequency was 112 ms from the start of fixation in the normal text condition, and 152 ms in the unsegmented text condition. This delay in the temporal onset of word frequency effects in the unsegmented text condition strongly suggests that removing spaces delays the word identification stage of reading. Possible underlying mechanisms are discussed, including lateral masking and word segmentation.

Keywords:

• Distributional analysis
• Eye movements
• Lexical processing
• Reading
• Word frequency

Acknowledgements

This research was supported by an NSERC grant to EMR and by grant HD26765 from the National Institute of Health to KR.

Notes

¹The location and target region analyses were also conducted using outlier rejection cutoff points. Specifically, in these analyses, we excluded all trials in which the first fixation on the target was below 80 ms or above 1000 ms. The percentage of outlier trials was extremely small (i.e., 1.7% for the normal condition and 1.4% for the unsegmented condition in Experiment 1A, and 1.2% for the normal condition and 0.9% for the unsegmented condition in Experiment 1B). Since the exclusion of these outlier trials did not affect the pattern of results, we reported the results without outlier rejection in the main text.

²Although the word frequency effects for the global measures were small in magnitude (see Table 1), they were nonetheless significant. These effects were likely driven by differences in the processing of the target words rather than from global differences in the processing of the entire sentence.

³We also used the survival analysis technique to examine the single-fixation and gaze duration measures, and our results were qualitatively similar to the first-fixation measure. Specifically, in Experiment 1A, the single-fixation divergence points were 100 ms in the normal condition and 166 ms in the unsegmented condition, and the gaze duration divergence points were 100 ms in the normal condition and 151 ms in the unsegmented condition. In Experiment 1B, the single-fixation divergence points were 142 ms in the normal condition and 178 ms in the unsegmented condition, and the gaze duration divergence points were 135 ms in the normal condition and 169 ms in the unsegmented condition. In the main text, we focus on the first-fixation measure that has been used in previous investigations (e.g., Reingold et al., 2012).