Frequency of regressive eye-movements for each sentence region as a difference from the control condition.

(a) Length-corrected first-pass reading times, and (b) frequency of regressive eye-movements for each anomaly condition, in the two-word region containing the verb (region 3). Error bars show standard errors.

To examine the running record of eye-movements as a sentence unfolds, we initially divided each target sentence into six regions of approximately two words each, for the purpose of aggregating reading times and classifying leftward eye-movements, as shown in Figure 3. For each sentence frame, corresponding regions contain the same numbers of words in all six versions.

Thirty-six sentence frames were devised to allow introduction of anomaly through manipulation of the main verb. Subject noun length was also varied within each frame. Three anomaly conditions were crossed with two noun length conditions to generate six versions of each sentence; see Figure 2. The anomaly conditions, syntactic anomaly, pragmatic anomaly, and non-anomalous control, were fashioned by alternating the main verb within each sentence frame. In the syntactic anomaly condition the inflection of the verb conflicted with a preceding modal, but pragmatic congruity was preserved. In the pragmatic anomaly condition, the verb’s pragmatic content was incongruous with the subject noun phrase, yet syntactic congruity was retained. Finally, in the control condition, both the verbal inflection and meaning were congruous with preceding material. Crucially, the syntactic anomaly introduces a violation of grammatical principles, while the pragmatic anomaly does not. Subject nouns are either Long (mean length 9.94 letters, sd = 1.88) or Short (mean length 5.39 letters; sd = 1.18). Long and short nouns in each frame were selected to establish equivalent pragmatic expectations. Sentence frames contain 6–8 words after the anomaly (mean = 7.19, sd = .47). Other than the alternations of main verb and subject noun, the lexical content of each frame was held constant.

Pursuing this possibility, the present study compares the eye-movement patterns of subjects as they read (for meaning) sentences containing anomalies of verbal morpho-syntax, and anomalies that depend on the relationship between sentence meaning and real-world probabilities (we refer to these as pragmatic anomalies), and non-anomalous sentences. Each type is illustrated in Figure 1; sentence (1a) is rendered anomalous by introducing a syntactic violation while keeping the meaning transparent and plausible, while (1b) is made pragmatically anomalous by a word that makes the content odd or absurd without compromising grammatical correctness. One measure on which we might expect to find evidence supporting a distinction in the way the parser copes with syntactic and pragmatic anomaly is in the time the eyes linger in the region of the anomalous word. For example, if the parser's sensitivity to syntactic information is manifested earlier in time than its sensitivity to aspects of sentence meaning (e.g. Boland, 1997; McElree & Griffith, 1995), we might see longer eye fixations at a word that is syntactically unexpected than at a word that is pragmatically unexpected. But in a recent study of anomalous sentences conducted in our laboratory (Ni, Fodor, Crain, & Shankweiler, 1998), from which the sentences in Figure 1 are drawn, we found no evidence in the eye-movement record of a delay in initial sensitivity to pragmatic constraints (see also Murray & Rowan, 1998). Detection of the two kinds of anomaly was rapid and simultaneous. Thus there was no support for the prior availability of syntactic information within the parsing mechanism.