Language Constraints and the Functional Stimulus in Reading. Technical Report No. 194.

This report evaluates evidence that language constraints influence the functional stimulus in reading. Three possible types of influences are discussed: influences on where the eyes are sent, on what region of text is attended during a fixation, and on what aspects of the text within this region are attended and used for reading. While there is evidence for contextual facilitation in reading, it has not yet been shown that this is due to changes in what aspects of the text stimulus are being perceived. Functional Stimulus in Reading 2 Language Constraints and the Functional Stimulus in Reading In the struggle to understand how perception takes place in a particular task such as reading, two primary questions can be asked. First, what is serving as the functional stimulus for the perception, and second, what is the nature of the perceptual activities by which the use of this stimulus information yields its effects? The first of these questions is the most directly empirical in nature. If empirical data can specify the functional stimulus for perception under certain conditions, then the task of understanding the mental activities of perception under those conditions can be addressed more profitably. Without good evidence about what is actually serving as the stimulus, further theorizing about perceptual activities is on somewhat shaky ground, being based on unsupported assumptions concerning what aspects of the visual information are actually being used. The purpose of the present paper is to consider the nature of the functional stimulus in reading; that is, what aspects of the text stimulus are being attended to or used for reading. The discussion of this topic requires that a distinction be made between visual information and contextual information. This is a common distinction in the literature, but the boundary between the two categories varies depending on the author's purposes and theoretical inclination. For the present paper, we will adopt a more extreme position than is usually taken. We use the term visual information to refer only to the visual characteristics of the text that are available during a particular fixation during reading. Contextual Functional Stimulus in Reading 3 information refers to all other information the reader has up to that point which places constraints on what the presently available visual information might be. This contextual information might have been gained from earlier portions of the text or simply be available from prior knowledge of the language, the nature of passages, the author's writing style, the topic being discussed, and so forth. The particular question we wish to address is whether contextual information produces changes in what visual information is acquired and used for reading during a fixation; that is, whether contextual information influences the functional stimulus. This is treated as an empirical question. We consider to some degree the evidence from tasks that do not involve normal reading, as well as studies of reading itself. We evaluate the evidence for the frequently made claim that contextual information influences what visual information is attended to and used during reading. The assumption that such influences exist has been prominent in the reading field for decades. The primary concern has been with the way contextual information influences visual processing. Different theorists have provided different possible explanations (for example, see Goodman, 1967; Hochberg, 1970; Neisser, 1967; Rumelhart, 1977). This assumed use of contextual information to control what serves as the functional stimulus in reading is often spoken of as an example of higher-level processes influencing lower-level processes. Functional Stimulus in Reading 4 Studies Involving Tasks Other Than Skilled Silent Reading There have been many studies which have demonstrated contextual facilitation of perception in tasks using language-based stimuli (e.g., letters, words and sentences). Two types of such research deal with perception of language in noise and perception of printed language presented