Читать книгу The Science of Reading - Группа авторов - Страница 16

We begin with the lower left portion of the Reading Systems Framework, the visual input that initiates the identification of a printed word. Pre‐dating modern‐day observations that the brain was not designed for reading (e.g., Dehaene, 2009), Huey (1908) pointed out that reading is “intensely artificial.” “The human eye and the human mind, the most delicate products of evolution, were evolved in adaptation to conditions quite other than those of reading” (p. 8).

The core visual constraint is that the acuity needed to identify a specific letter within a word is limited to one to two degrees of visual angle at normal viewing distance. Within this narrow window, only a single word or two (with the help of parafoveal viewing) can be identified during an eye fixation, although less precise visual information is available peripherally.

As detailed by Liversedge et al. (this volume), readers adapt to this limitation by making frequent eye‐fixations, directly fixating on between 60% and 80% of content words (Rayner et al., 2005). They also adjust their fixation rates (and the number of regressions) in response to text difficulty and reading goals, one of the key regulatory strategies in reading. Word fixations vary in duration, generally allowing three to five words to be fixated within a second of reading (Rayner et al., 2004, 2005). With assistance from word properties, context, and parafoveal viewing, a reader may approximate the reading rate implied by Gough’s (1972) one second of reading. The familiarity of a word, its predictability from context (Rayner et al., 2004), and the structure of the sentence (Clifton & Staub, 2011) all exert an effect on eye movement measures. Some measures reflect the more passive, automatized aspects of word identification (e.g., fixation durations), whereas others also reflect regulatory processes that help the reader make sense of the text (e.g., regressions). Together, eye‐tracking measures reflect how context and the linguistic properties of words affect how easily they are read and understood.

Skilled readers control their eye movements to accommodate the perceptual constraints on word identification while maintaining reading efficiency. How this is accomplished is the target of eye‐movement control models. Serial processing models assume that only a single word is in visual attention, for example, the EZ Reader model (Reichle et al., 1998, 2003). To accomplish rapid reading rates with serial processing, the brain must signal an eye movement before the word has been identified completely because the movement lags behind the brain’s launch signal. Thus, EZ Reader assumes a signal that word identification is imminent (not complete) is what prompts an eye movement. This signal comes earlier for a familiar word or one predictable from context. An alternative solution to perceptual constraints is to allow parallel processing on adjacent words (SWIFT model, Engbert et al., 2005). A more recent model allows for parallel processing of words and provides specific word identification mechanisms (Snell et al., 2018). The question of parallel versus serial processing of words remains a point of contention (see Grainger, and Liversedge et al., this volume).