British English norms for the spontaneous completion of three-letter word stems

Word stem completion tasks involve showing participants a number of words and then later asking them to complete word stems to make a full word. If the stem is completed with one of the studied words, it indicates memory. It is a test widely used to assess both implicit and explicit forms of memory. An important aspect of stimulus selection is that target words should not frequently be generated spontaneously from the word stem, to ensure that production of the word really represents memory. In this article, we present a database of spontaneous stem completion rates for 395 stems from a group of 80 British undergraduate psychology students. It includes information on other characteristics of the words (word frequency, concreteness, imageability, age of acquisition, common part of speech, and number of letters) and, as such, can be used to select suitable words to include in a stem completion task. Supplemental materials for this article may be downloaded from http://brm .psychonomic-journals.org/content/supplemental.     

A collection of 4,741 word fragments that have unique completions with respect to 146,205 words

A collection of 4,741 word fragments that have a unique completion is described. All word fragments are specified by two letters (e.g.,__Q__U__can only be completed by the word LIQUEURS). The words completing these fragments range in length from five to nine letters. The fragments are unique with respect to a pool of 146,205 words, which helps rule out the possibility that obscure words could be used as a completion to the fragments. The collection of fragments as well as the words that complete them is available in ASCII format on computer disks or in printed form.     

Determinants of word fragment completion

A current debate in the memory literature concerns the validity of word fragment completion (WFC) as a test of implicit memory. It has been claimed that language variables exert a strong influence on the task, and that the task reflects memory only to a small extent (Hintzman & Hartry, 1990). For these reasons, the use of contingency analyses of recognition and WFC performance as a means of studying underlying memory processes has been criticized. The present study addressed this issue by examining the influence of language variables on completion of a set of computer generated single-solution fragments of Swedish words (Olofsson & Nyberg, 1992). It was found that language variables indeed had a large effect on completion performance, and that priming only accounted for a small portion of variance in the task. It is therefore suggested that the method of triangulation should be employed for contingency analyses involving WFC.     

Abstractionist versus exemplar-based theories of visual word priming: A subsystems resolution

Three experiments addressed abstractionist versus exemplar-based theories of the visual representations underlying word priming. Participants first read centrally presented whole words (each displayed in all lowercase or in all uppercase letters), and then they completed laterally presented word stems (each displayed in all lowercase or in all uppercase letters). Word stem completion priming was letter-case specific (greater for same-case primed items than for different-case primed items) when stems were presented directly to the right cerebral hemisphere but not when stems were presented directly to the left cerebral hemisphere. This interaction was not influenced by the typicality of the test stems, but it was observed only for stems composed of letters with visually dissimilar lowercase and uppercase structures (e.g., bea/BEA) and not for stems composed of letters with visually similar lowercase and uppercase structures (e.g., sco/SCO). In contrast, cued recall was letter-case specific when similar-case or dissimilar-case stems were presented directly to the right hemisphere. Results do not support strongly abstractionist or exemplar-based theories. Instead, they suggest a resolution to these differing perspectives: Relatively independent neural subsystems operate in parallel to underlie abstract-category and specific-exemplar priming of word forms.     

Direct comparison of two implicit memory tests: word fragment and word stem completion.

In 3 experiments, the implicit memory tests of word fragment and word stem completion showed comparable effects over several variables: Study of words produced more priming than did study of pictures, no levels-of-processing effect occurred for words, more priming was obtained from pictures when Ss imaged the pictures' names than when they rated them for pleasantness, and forgetting rates were generally similar for the tests. A different pattern of results for the first 3 variables occurred under explicit test conditions with the same word fragments or word stems as cues. We conclude that the 2 implicit tests are measuring a similar form of perceptual memory. Furthermore, we argue that both tests are truly implicit because they meet Schacter, Bowers, & Booker's (1989) retrieval intentionality criterion: Levels of processing of words have a powerful effect on explicit versions of the tests but no effect on implicit versions.     

Completion norms for 40 three-letter word stems

This is a report of the completion responses for 40 three-letter word stems (e.g., ABO) produced by 100 undergraduate students at the University of California at San Diego. The report includes a list of the different words that were written as stem completions, their frequency of occurrence as completions, and their frequency of occurrence in English according to published norms. This list of materials is useful for the construction of completion tests for future investigations of direct priming phenomena, and it may provide an important covariate in the analysis of performance on completion tests. Preliminary analyses of the results reveal three primary factors that determine overall performance on a stem-completion test: word frequency, word length, and meanings per word. Analyses of the completions produced for each individual word stem, however, reveal that usually only one of these factors makes a significant contribution to performance.     

Repetition effects on word fragment completion: The role of competition among responses

Four experiments examined the effect of spaced repetition of study words on completion of word fragments with only one solution and word fragments with multiple solutions. Recognition was used as test of explicit memory in the first two experiments. The study words were presented either once or three times. Repetition was found to increase recognition memory substantially, and to affect fragment completion performance only marginally. This was true for both single- and multiple-solution fragments, showing that competition among responses is not critical for the magnitude of the repetition effect in fragment completion. This finding, that the repetition effect is marginal also when the type of cues provides an occasion for repetition effects to show up, suggests that the real effect of repetition on perceptual priming is borderline. It is proposed that memory from the first presentation eliminates necessary processing of items when they are re-exposed, and that the repetition effect thereby is reduced.     

Perceptual grouping in visual word recognition

Four experiments are presented in which printed texts are read for their meaning. Some of the texts were mutilated by altering the size of selected letters. In Experiments 1, 2, and 3, the number of words mutilated per passage and the number of letters changed per word were both manipulated. In all three experiments, reading was slowed as a function of the number of words changed per passage, while the number of letters changed per word had a much smaller effect. The interaction between the number of words and number of letters changed was not significant in any of the experiments. It is difficult to explain these results merely in terms of changes in the discriminability of letters. In Experiment 2 all uppercase text was used, which argues against an explanation in terms of supraletter features such as word envelope. We propose an explanation in terms of visual attention and the perceptual grouping required prior to feature recognition. The last experiment supports this explanation through the counterintuitive finding that adding letters of intermediate size can improve legibility by allowing grouping processes to associate large and small letters as belonging to the same word object.     

Difficulty and familiarity norms for 192 single-solution word fragments

Normative data are presented for the probability of successfully completing 192 single-solution word fragments. Normative data on the familiarity of college students with the solution words are also given, along with estimates of word frequency from existing norms. Regression analyses were performed in order to predict fragment completion difficulty from familiarity, frequency, and several structural characteristics of the fragments. Familiarity, whether or not first and/or last letters appeared in the fragment, and the ratio of letters to missing letters in the fragment were included in the regression equation as significant predictors of difficulty for this fragment set.     

Some linguistic determinants of Swedish word recognition

Native Swedish words and words of foreign origin were studied in a word fill-in task (Experiment 1), in a task in which words were explicitly classified as being native or loan words (Experiment 2), and in a lexical decision task in which a small onset asynchrony was introduced in displaying a word's letter pattern (Experiment 3). The findings obtained show that, both in simple printed word recognition and when asked to make explicit judgments about origin, readers are sensitive to phonological features of words not marked in Swedish orthography. It was further found that previewing a substring of word-initial letters which determines a word's root morpheme will prime recognition, whereas previewing a randomly selected pattern of letters inhibits recognition.     

How to drastically reduce priming in word stem completion—and still present the words

This paper describes a series of experiments in which we demonstrated that "dysphonemic" word stems, which are likely not pronounced in isolation as they are within a word (e.g., MUS in MUSHROOM or LEG in LEGEND), showed less priming than did "phonemic stems" (e.g., MUS in MUSTARD or LEG in LEGACY). Furthermore, words with either dysphonemic or phonemic three-letter stems gave rise to equivalent levels of priming when test cues were four-letter stems (LEGE) or word fragments (L_G_ND). Moreover, the difference between phonemic and dysphonemic stems persisted when nonpresented completion rates were matched. A final cued-recall experiment revealed that performance was greater for phonemic stems than for dysphonemic stems and that this difference was greater for older participants than for younger ones. These results are not readily accounted for by extant theoretical approaches and point to important methodological issues regarding stem completion.     

Word-fragment cuing: the lexical search hypothesis

In four experiments we evaluated aspects of the hypothesis that word-fragment completion depends on the results of lexical but not semantic search. Experiment 1 showed that the number of meaningful associates linked to a studied word does not affect its recovery when the test cue consists of letters and spaces for missing letters. Experiments 2 and 3 showed retroactive interference effects in fragment completion when words in a second list were lexically related to words in a first list but not when the words in the second list were meaningfully related. Experiment 4 indicated that for studied words, instructions to search at the word level facilitated completion performance and that instructions to generate letters to fill missing spaces had no effect. Other findings indicated that completion was affected by the number of words lexically related to the fragment and by the number of letters missing from the fragment. In general, experimental manipulations that focused on lexical characteristics were effective, and those that focused on semantic characteristics were ineffective. The findings support the conclusion that word fragments engender a lexical search process that does not depend on retrieving encoded meaning.     

Recency effects for meaning and form in word selection

Three experiments examined the contribution of phonological availability in selecting words as predicted by interactive activation models of word production. Homophonous words such as week and weak permitted a word's phonological form to be activated on priming trials without selection of its meaning or lemma. Recent production of a homophone failed to significantly increase production of its twin as a sentence completion. However, speakers were significantly more likely to complete a sentence with a recently read or generated unambiguous word. This increase in response probability was unaffected by word frequency. The results constrain the degree to which experience and phonological availability may affect word selection in spoken language production.     

Normative data on the familiarity and difficulty of 196 Spanish word fragments.

In this article, normative data on the familiarity and difficulty of 196 single-solution Spanish word fragments are presented. The database includes the following indices: difficulty, familiarity, frequency, number of meanings, number of letters given in the fragment, first and/or last letters given, and ratio of letters to blanks. A factor analysis was performed on difficulty, and two factors were obtained. Frequency, familiarity, and number of meanings loaded highly on the first factor, which we consider to measure lexical processes, whereas number of letters in the fragment, first and/or last letters given, and ratio of letters to blanks loaded highly on the second factor, which we judge to be determined by perceptual information. Regression analyses using factor scores as predictors showed that both factors accounted for a significant part of the completion probability scores. The full set of these norms may be downloaded from the Psychonomic Society Web archive at www.psychonomic.org/archive/.     

Letters and words in word identification

Studies by Barron and Henderson (1977) and Johnson (1975) provide evidence that whole words may be the unit of identification in word perception, rather than single letters. Johnson found that words were matched faster than a letter to the first letter in a word. Barron and Henderson found faster matching times for words than for legal non-word items in a letter-matching task. These findings support the interpretation that words are identified before individual letters. If so, a word-frequency effect should be expected. Experiments 1 and 2 tested for word vs. first-letter-in-word differences, as well as for a word-frequency effect in simultaneous and delayed visual matching tasks. In the simultaneous task, first letters in words were matched faster than words. In the delayed task, there was no difference between matching words or matching the first letters in words. With both tasks there was a word-frequency effect for word matches but not for first-letter-in-word matches. In Experiment 3, first-letter matching time was unrelated to word frequency or lexical status, although it did vary with orthographic legality. These results, on the whole, are consistent with a race model in which identifications take place simultaneously at word, letter-cluster, and letter levels, rather than a sequential model in which the whole word is identified before the component letters.     

Reexamining the word length effect in visual word recognition: New evidence from the English Lexicon Project

In the present study, we reexamined the effect of word length (number of letters in a word) on lexical decision. Using the English Lexicon Project, which is based on a large data set of over 40,481 words (Balota et al., 2002), we performed simultaneous multiple regression analyses on a selection of 33,006 English words (ranging from 3 to 13 letters in length). Our analyses revealed an unexpected pattern of results taking the form of a U-shaped curve. The effect of number of letters was facilitatory for words of 3–5 letters, null for words of 5–8 letters, and inhibitory for words of 8–13 letters. We also showed that printed frequency, number of syllables, and number of orthographic neighbors all made independent contributions. The length effects were replicated in a new analysis of a subset of 3,833 monomorphemic nouns (ranging from 3 to 10 letters), and also in another analysis based on 12,987 bisyllabic items (ranging from 3 to 9 letters). These effects were independent of printed frequency, number of syllables, and number of orthographic neighbors. Furthermore, we also observed robust linear inhibitory effects of number of syllables. Implications for models of visual word recognition are discussed.     

Form-Specific Visual Priming in the Left and Right Hemispheres

Word fragment completion performance was examined for items that were presented in the same or different letter case at study and test. During the study phase words and nonwords were presented at central fixation, then during the test phase a divided visual field technique was used in which word fragments were presented briefly to the right hemisphere (left visual field) or the left hemisphere (right visual field). Previous research using the word stem completion task indicated that only the right hemisphere was sensitive to case changes in words from study to test. In contrast, the current results indicate that in the fragment completion task the priming effects for the test items presented to either hemisphere were greater when the fragments were in the same compared to different letter case at study and test. These results indicate that both hemispheres are capable of supporting form-specific visual implicit memory.     

Normative data on the familiarity and difficulty of 196 Spanish word fragments

In this article, normative data on the familiarity and difficulty of 196 single-solution Spanish word fragments are presented. The database includes the following indices: difficulty, familiarity, frequency, number of meanings, number of letters given in the fragment, first and/or last letters given, and ratio of letters to blanks. A factor analysis was performed on difficulty, and two factors were obtained. Frequency, familiarity, and number of meanings loaded highly on the first factor, which we consider to measure lexical processes, whereas number of letters in the fragment, first and/or last letters given, and ratio of letters to blanks loaded highly on the second factor, which we judge to be determined by perceptual information. Regression analyses using factor scores as predictors showed that both factors accounted for a significant part of the completion probability scores. The full set of these norms may be downloaded from the Psychonomic Society Web archive atwww.psychonomic.org/archive/.     

Comparing word fragment completion and cued recall with letter cues

Cued recall with word stems as cues and fragment completion rely on different types of letter cues and also differ in the explicit-implicit nature of the retrieval orientation. Despite these differences, variables effective in one task may be effective in the other because both rely on letter cues. Two variables known to affect cued recall were manipulated: Lexical set size (number of words that fit the letter cue) and meaning set size (number of associates generated to the studied words). Across four experiments, subjects in each task were less likely to recover targets from larger lexical sets. However, meaning set size affected cued recall but not fragment completion. These results indicate that fragment completion and letter-cued recall are based on lexical search but that cued recall also involves a semantic search component. Furthermore, type of retrieval cue had a greater effect than type of retrieval orientation.     

Effects of increased letter spacing on word identification and eye guidance during reading

The effect of increasing the space between the letters in words on eye movements during reading was investigated under various word-spacing conditions. Participants read sentences that included a high- or low-frequency target word, letters were displayed normally or with an additional space between adjacent letters, and one, two, or three spaces were present between each word. The spacing manipulations were found to modulate the effect of word frequency on the number and duration of fixations on target words, indicating, more specifically, that letter spacing affected actual word identification under various word-spacing conditions. In addition, whereas initial fixations landed at the preferred viewing position (i.e., to the left of a word’s center) for sentences presented normally, landing positions were nearer the beginnings of words when letter spacing was increased, and even nearer the beginnings of words when word boundary information was lacking. Findings are discussed in terms of the influence of textual spacing on eye movement control.