Improving reading rate prediction with word length information: Evidence from Dutch

Previous research in English has suggested that reading rate predictions can be improved considerably by taking average word length into account. In this study, we investigated whether the same regularity holds for Dutch. The Dutch language is very similar to English, but words are on average half a letter longer: 5.1 letters per word (in non-fiction) instead of 4.6. We collected reading rates of 62 participants reading 12 texts with varying word lengths and examined which change in the English equation accounts for the Dutch findings. We observed that predictions were close to the best-fitting curve as soon as the average English word length was replaced by the average Dutch word length. The equation predicts that Dutch texts with an average word length of 5.1 letters will be read at a rate of 238 words per minute (wpm). Texts with an average word length of 4.5 letters will be read at 270 wpm, and texts with an average word length of 6.0 letters will be read at a rate of 202 wpm. The findings are in line with the assumption that the longer words in Dutch do not slow down silent reading relative to English and that the word length effect observed in each language is due to word processing effort and not to low-level visual factors.