Fast word reading in pure alexia: “fast, yet serial”

Abstract

Pure alexia is a severe impairment of word reading in which individuals process letters serially with a pronounced length effect. Yet, there is considerable variation in the performance of alexic readers with generally very slow, but also occasionally fast responses, an observation addressed rarely in previous reports. It has been suggested that “fast” responses in pure alexia reflect residual parallel letter processing or that they may even be subserved by an independent reading system. Four experiments assessed fast and slow reading in a participant (DN) with pure alexia. Two behavioral experiments investigated frequency, neighborhood, and length effects in forced fast reading. Two further experiments measured eye movements when DN was forced to read quickly, or could respond faster because words were easier to process. Taken together, there was little support for the proposal that “qualitatively different” mechanisms or reading strategies underlie both types of responses in DN. Instead, fast responses are argued to be generated by the same serial-reading strategy.

Keywords:

• alexia
• pure alexia
• letter-by-letter reading
• eye movements
• serial versus parallel processing

Acknowledgments

We are indebted to DN for participation in our research which included hours of testing and discussions about our intuitions about reading. Professor Wolf Lagrèze kindly provided the Goldmann perimetry, Professor Martin Arguin kindly provided letter-confusability values. Parts of the results were presented at the 30th European Workshop on Cognitive Neuropsychology in January 2012. We would like to thank the audience for helpful discussion.

Notes

^1. The terms LBL reading and pure alexia have often been used interchangeably. Formally, “pure alexia” refers to the selective deficit of reading with preserved writing while LBL reading describes the reading strategy of many patients with pure alexia. A length effect in word reading, however, may also be observed in other neurological conditions.

^2. This was part of another study (Bormann, Wolfer, Hachmann, Largèze, & Konieczny, 2013) which assessed in detail the differences between pure alexic readers and unimpaired readers with a simulated visual field defect (sVFD; cf. Sheldon et al., 2012). DN’s eye movements and response times were compared to controls reading with a simulated sectoranopia matching DN’s visual deficit. The sVFD led to slower responses which, however, were still significantly slower than DN’s reading. Unlike pure alexic readers, controls reading with a sVFD did not exhibit a comparable length effect.

^3. Interrater reliability between two raters judging independently the onset of DN’s correct responses was r = 0.998 (p < 0.01).

^4. This refers to the measure of “interest area first fixation duration”, that is, the duration of the first fixation upon each interest area (i.e., letter).

^5. We do not mean to do associate Howard (1991) with a theoretical position he may not have intended. If “serial” and “parallel” processing are understood as occurring simultaneously instead of being mutually exclusive then our results are compatible with his conclusions. The quote, however, suggests the reading strategies to be mutually exclusive.

^6. The conclusions apply, thus, primarily to the present experimental paradigm and the exposure durations employed in these experiments. We cannot exclude the possibility that DN would have been able to read letters in parallel if presentation interval was shorter than 1 s.