Cogn Neuropsychol. 2002 Sep 1;19(6):535-55. doi: 10.1080/02643290244000040.
Four experiments are reported that focus on the issue of sequential vs. parallel letter processing in letter-by-letter (LBL) dyslexia; these were conducted on patient IH. Expt. 1 showed a large linear reduction of word naming times with an increase in the number of orthographic neighbours of the target (i.e., words of the same length differing by just one letter; N size). Given the large negative linear correlation existing between word length and N size, this result raises the possibility that the large word length effect diagnostic of LBL dyslexia may be, in fact, an artefact of uncontrolled N size. Expt. 2 falsified this possibility by showing that the word length effect is unaffected by whether N size is controlled for or not. This result also suggested that the facilitatory effect of increased N size in LBL dyslexia is based on the parallel processing of the constituent letters of the target. Further supporting a contribution of parallel letter processing to overt word recognition performance in the disorder, Expt. 3 showed significant but independent effects of word length and letter confusability (i.e., similarity of the constituent letters of the target word with other letters of the alphabet). The letter confusability effect therefore appears to rest on the parallel analysis of the letters in the target word. Finally, Expt. 4 showed that the facilitatory effect of N size is prevented with high letter-confusability targets. These observations suggest that LBL dyslexia rests on an impairment of letter encoding that results in an excessive level of background noise in the activation of lexical-orthographic representations when letters are processed in parallel. This prevents overt identification of the target and forces sequential letter processing in order to achieve this goal.
报告了四项实验，这些实验主要关注在逐个字母（LBL）阅读障碍中顺序与平行字母处理的问题；这些实验都是在患者 IH 身上进行的。实验 1 表明，目标的正字法邻居数量（即，长度相同但仅相差一个字母的单词；N 大小）增加时，单词命名时间会呈线性大幅减少。鉴于单词长度和 N 大小之间存在较大的负线性相关性，这一结果表明，LBL 阅读障碍中较大的单词长度效应可能实际上是不受控制的 N 大小的人为产物。实验 2 通过表明单词长度效应不受 N 大小是否受控制的影响而否定了这种可能性。这一结果还表明，LBL 阅读障碍中 N 大小增加的促进作用基于目标字母的平行处理。进一步支持了平行字母处理对该障碍中显性单词识别性能的贡献，实验 3 表明，单词长度和字母混淆度（即，目标单词的组成字母与字母表中其他字母的相似性）都有显著但独立的影响。因此，字母混淆度效应似乎取决于目标单词中字母的平行分析。最后，实验 4 表明，高字母混淆度目标会阻止 N 大小的促进作用。这些观察结果表明，LBL 阅读障碍源于字母编码的损伤，当字母平行处理时，会导致词汇-正字法表示的激活中出现过度的背景噪声，从而阻止目标的显性识别，并迫使进行顺序字母处理以实现这一目标。
