Donald J. Foss

A discourse on semantic priming.

Abstract The processing of a word is sometimes affected if earlier words are semantically related to it (semantic “priming”). Priming phenomena have generally been interpreted as reflecting the organization of the mental lexicon. Past studies have shown that priming effects have a very fast rise time and a relatively rapid decay time. This paper investigates the rate of decay of semantic facilitation in both sentences and lists. It was hypothesized that sentence processing involves the construction of a discourse model in which the main topics stay active. If true, then words referring to related objects or events will be processed rapidly even if they occur later in the input, i.e., there will be no decay of facilitation. Three experiments with college students examined the relative time to process a critical word when it was preceded by either a pair of semantically related words or more neutral words. The materials occurred in either sentences or lists, the latter being word-level anagrams of the sentences. Subjects carried out the phonememonitoring task, responding to a word-initial target phoneme that occurred immediately after the critical word. In Experiments I (N = 58) and II (N = 40) 12 words separated the related/neutral words and the critical items. Facilitation in processing the critical word was present in sentences but not in lists. Experiment III (N = 128) showed that the amount of facilitation in sentences was the same when 12 words separated the related/neutral and critical words as when 1.5 words separated them. Thus, there was no evidence obtained here for decay of facilitation in sentences. The results are taken to be consistent with a discourse-model interpretation of semantic facilitation in sentences.

Text Structure and Reading Time for Sentences.

Two experiments examining the influence of a storys structure on the comprehension of its sentences are presented. It was expected that sentences at high levels in a story would take longer to encode than those at low levels, either because cues to the sentences roles exist within the story or because of differential difficulty of integrating the sentences into the prior context. Moreover, the greater density of new information early in stories might result in comprehension being affected by the serial position of a sentence within a story. The reading times for the individual sentences (or clauses) of stories were measured where a particular sentence appeared at one hierarchical (and/or serial) position in one story and at a different hierarchical (and/or serial) position in another story. In both experiments high-level sentences took longer to read than low-level ones and early-occurring sentences longer than late-occurring ones. Recall data supported the structural assignment of the critical sentences. These results were discussed both in terms of the initial hypotheses and in terms of W. Kintsch and T. A. van Dijks (Psychological Review, 1978, 85, 363–394) theory of text comprehension.

On the role of sentence stress in sentence processing

Words bearing high stress appear to be easier to process during sentence comprehension. Since sentence stress typically falls on content words this suggests that comprehension is organized according to a form class bias: process stressed items as content words. The present study measured reaction-time (RT) to word-initial phoneme targets on content and function words in sentence contexts. Half of the words of each type were stressed, half were not. In addition, a variable of normality of stress pattern was manipulated. It was found that RTs were shorter for stressed items independent of their syntactic function. No effect for content v. function words or normal v. non-normal stress pattern was observed. Results were interpreted within the framework of a predictive model utilizing the concept of semantic focus.

Decision processes during sentence comprehension: Effects of lexical item difficulty and position upon decision times

In this study 40 college S s listened to 60 English sentences and attempted to, ( a ) press a button whenever a word in a sentence began with a /b/, and ( b ) comprehend the sentences. Reaction times (RT) of the button-push responses were recorded. The words starting with /b/ (target words) occurred either early or late in the sentences and, in addition, they were immediately preceded by words of either high or low frequency in the language. Average RT was significantly longer when the target word occurred after low frequency or hard words than when the target word occurred after easy words. In addition, RT was significantly longer when target words occurred early as opposed to late in the sentences. The results were discussed in terms of a decision-making conception of sentence comprehension.

Some effects of context on the comprehension of ambiguous sentences

Ambiguous and unambiguous sentences were presented to 80 subjects in Experiment I. Half of the ambiguous sentences had contexts which biased the interpretation of the ambiguity and half had neutral contexts. The subjects monitored the sentences for a specified target phoneme and reaction times (RTs) for the monitoring responses were collected. In both neutral and biased contexts the RTs were longer when the target phoneme occurred shortly after an ambiguous word than when it occurred after an unambiguous control word. The results were the same both for those subjects who noticed that the sentences were ambiguous and for those who did not. Experiment II replicated Experiment I. Mechanisms of sentence processing were discussed and a model patterned after common sense was discarded.

Identifying the speech codes.

Models of speech processing typically assume that speech is represented by a succession of codes. In this paper we argue for the psychological validity of a prelexical (phonetic) code and for a postlexical (phonological) code. Whereas phonetic codes are computed directly from an analysis of input acoustic information, phonological codes are derived from information made available subsequent to the perception of higher order (word) units. The results of four experiments described here indicate that listeners can gain access to, or identify, entities at both of these levels. In these studies listeners were presented with sentences and were asked to respond when a particular word-initial target phoneme was detected (phoneme monitoring). In the first three experiments speed of lexical access was manipulated by varying the lexical status (word/nonword) or frequency (high/low) of a word in the critical sentences. Reaction times (RTs) to target phonemes were unaffected by these variables when the target phoneme was on the manipulated word. On the other hand, RTs were substantially affected when the target-bearing word was immediately after the manipulated word. These studies demonstrate that listeners can respond to the prelexical phonetic code. Experiment IV manipulated the transitional probability (high/low) of the target-bearing word and the comprehension test administered to subjects. The results suggest that listeners are more likely to respond to the postlexical phonological code when contextual constraints are present. The comprehension tests did not appear to affect the code to which listeners responded. A “Dual Code” hypothesis is presented to account for the reported findings. According to this hypothesis, listeners can respond to either the phonetic or the phonological code, and various factors (e.g., contextual constraints, memory load, clarity of the input speech signal) influence in predictable ways the code that will be responded to. The Dual Code hypothesis is also used to account for and integrate data gathered with other experimental tasks and to make predictions about the outcome of further studies.

Some effects of ambiguity upon sentence comprehension

Three groups of 20 S s were auditorily presented with 24 ambiguous and 24 unambiguous sentences. One group was asked to push a button whenever a particular phoneme occurred. Reaction time (RT) for this response was significantly longer in ambiguous sentences. A second group had to classify each sentence as ambiguous or not after it was presented. Lexical ambiguities were discovered somewhat faster than underlying structure ambiguities. A third group performed both of these tasks. In this group, RT to monitor for the phoneme was longer for ambiguous than for unambiguous sentences only when S himself classified the sentence as ambiguous. The S s in the third group were significantly slower on both tasks.

On the Psychological Reality of the Phoneme: Perception, Identification, and Consciousness.

In Experiment I, 40 subjects listened to 100 lists of two-syllable words. They monitored each list for the presence of either a specified word or an initial syllable of a word. Reaction times to respond to these targets were recorded. Reaction times were significantly shorter when the target was a two-syllable word. In Experiment II, 45 subjects listened to the lists and monitored for either a two-syllable word, the initial syllable of a word, or the initial phoneme of a word. Reaction times were shortest for word targets and longest for phoneme targets. Implications of these findings for the “reality” of the units was discussed. A distinction between perception and identification was introduced and, in addition, a proposal about a determinant of consciousness was forwarded.

Decision processes during sentence comprehension: Effects of surf ace structure on decision times

Sentence comprehension is considered to be a set of decisions concerning the identification of entities at the various linguistic “levels.” Such decisions utilize overlapping fixed capacity psychological mechanisms. To the extent that one decision is difficult, others should take longer. This framework received support in two studies in which Ss’ reaction times (RT) to the presence of a phoneme in a sentence were measured. When surface structure syntax was difficult, as in self-embedded sentences, RT was longer (given that S comprehended the sentence) than when surface structure syntax was relatively easy. Additionally, the presence in surface structure of a putative cue for underlying structure did not affect RT, though comprehension was significantly inferior.

Semantic facilitation and lexical access during sentence processing

An experiment was conducted testing predictions derived from context-dependent and context-independent models of lexical access. Four types of unambiguous test sentences were constructed. The direct object of each test sentence was preceded by a verb that was either semantically related or unrelated to it, and by an adjective that was semantically related or unrelated. Context-dependent models predict that the speed with which the object noun is retrieved from the mental lexicon will be faster when the verb and/or the adjective is semantically related; context-independent models predict no such facilitation. Forty-four subjects each heard 32 test sentences and were asked to monitor within the sentence for a word-initial target phoneme. The target phoneme occurred on the word following the object noun. Reaction times to detect the targets were obtained. According to context-dependent models, these times should be shorter when related words precede the object noun, and that is what was found. It was also observed that the facilitation effects due to the related verbs and adjectives were additive. Implications of these results were discussed.