This research investigates the role played on shallow and deep levels of comprehension by textual changes that are aimed at: (a) improving the relationships within text ideas, and (b) producing better links between text ideas and the reader's knowledge. Four versions of a long physics passage were elaborated combining both kinds of textual changes. Four groups of tenth graders were each given one of the four versions. Different measures representative of these levels of comprehension were taken: getting main ideas, recall, and problem solving. The results indicated that: (a) main idea performance was affected by improving the relationships within text ideas, (b) both textual changes contributed separately to recall, and (c) problem solving increased only when the two changes were presented together. © 1998 Elsevier Science Ltd. All rights reserved Scientific texts are an important tool for learning and their improvement is a relevant educational issue. Since the 1980's, many studies have been developed to test the efficacy of certain textual changes. These changes may be classified into two groups: (a) changes aimed at improving the relationships within text ideas without adding new content facts to the original text, and (b) changes aimed at producing better links between text ideas and the reader's previous knowledge by adding new content facts to the text. We may call the former coherence textual changes, and the latter linking textual changes.Coherence textual changes refer to changes which, firstly, improve global coherence by explicitly including topical expressions such as headings, topic sentences, or summaries, (van Dijk, & Kintsch, 1983;Kieras, 1985), and secondly, increase connections from one idea to the next in the text. In the former, topical expressions facilitate the processes of macrostructure formation (Meyer, Brandt, & Bluth, 1980;Britton, Glynn, Meyer, & Penland, 1982). These processes are especially demanding in scientific texts given that readers generally have little previous knowledge of their content (Britton, Glynn, & Smith, 1985). In the latter, the *Departamento de Psicologia Evolutiva y de la Educacion [Department of Developmental and Educational Psychology], University of Valencia, P.O. Box 22045, 46071 Valencia, Spain. E-mail: Eduardo.Vidal-abarca@uv.es 215 increase in connections within an existing text can be accomplished in two ways: by re-stating textual ideas, and by making explicit certain implicit relationships presented in the original text.In general, a re-statement of textual ideas refreshes the memory and aids the reader in her textual understanding (Kintsch, & van Dijk, 1978;Britton, Van Dusen, Glynn, & Hemphill, 1990). In particular, scientific texts frequently present a series of premises and then a long chain of reasoning from which the reader must ultimately understand a given conclusion. However the novice reader may have difficulty following that chain of reasoning, especially if the premises were cited so long ago that the information needed to process t...