We compared immediate and delayed error correction during sight-word instruction with 5 students with developmental disabilities. Whole-word error correction immediately followed each error for words in the immediate condition. In the delayed condition, whole-word error correction was provided at the end of each session's three practice rounds. Immediate error correction was superior on each of the four dependent variables.DESCRIPTORS: developmentally disabled children, error correction, feedback, instructional design, reading, developmentally disabled childrenThe present study is an extension of two previous experiments that analyzed the characteristics of effective error correction during sight-word instruction with students with developmental disabilities. In the first study, whole-word error correction (the teacher stated the whole word and the student repeated it) provided after each sight-word reading error was more effective than phonetic-prompt error correction (the teacher provided phonetic prompts) for all 5 students (Barbetta, Heward, & Bradley, 1993). In the second study, whole-word error correction was implemented with and without the student repeating the correct response during each error-correction episode (Barbetta, Heron, & Heward, 1993). All 6 students in that study acquired and maintained words at a higher rate when each error-correction episode ended with the student making an active response, compared to the no-response procedure in which the students "paid attention" as the teacher modeled the correct response. The present study investigated the extent to which the acquisition and maintenance of sight words are influenced by the timing of whole-word error correction with an active student response: immediately following each error on a trialby-trial basis versus delayed until the end of the session on a massed practice basis.METHOD: Participants. Participants were I male and 3 female students, aged 7 to 9 years, enrolled in a self-contained class for students with developmental disabilities. Full-scale IQ scores ranged from 58 to 77. Student 1 read at the firstgrade level; the others read at preprimer to primer levels. Student 4's participation was shortened due to a family move.Procedure. Individualized pretesting was conducted each week to create a new set of 14 unknown words (printed on 3in. by 5 in. index cards and randomly assigned to immediate or delayed error correction). One-to-one instructional sessions on each word set were conducted 4 days per week. Each 10-to 12-min session consisted of (a) a teacher presentation of words (on the 1st day of instruction per set) or a next-day test, (b) three practice trial rounds with error correction (with words shuffled between rounds), and (c) a same-day test approximately 3 hr after instruction (for details, see Barbetta, Heward, & Bradley, 1993). During immediate error correction, immediately following each error, the teacher said, "No, this word is . What word?" The student repeated the word, and the teacher provided praise and presented t...