Processing Phonological and Semantic Ambiguity - Haskins

Haskins Laboratories Status Report 00 Speech Ruearch1992, SR-109/110, 191-204

Processing Phonological and Semantic Ambiguity:Evidence from Semantic Priming at Different SOAs*

Ram Frostt and Shlomo Bentint

Disambiguation of heterophonic and homophonic homographs was investigated in Hebrewusing semantic priming. Ambiguous primes were followed by unambiguous targets at 100ms, 250 ms, and 750 ms 80A. Lexical decision for targets related to the dominantphonological alternatives of heterophonic homographs were facilitated at all 80As.Targets related to subordinate alternatives were facilitated only at 80As of 250 ms orlonger. When the primes were homophonic homographs, semantic rehltionship facilitatedlexical decision to targets at all 80As regardleu of the dominance of the meaning to whichthe targets were related. These data can be accounted for by assuming multiple lexicalentries for heterophonic homographs, single lexical entries for homophonic homographsand phonological mediation of accessing meanings. Language specific factors probablyaccount for the long lasting activation of subordinate meanings.

Several studies of lexical disambiguationsuggested that all the meanings of a homographmay be automatically activated. One experimentalprocedure used to demonstrate access to multiplemeanings is semantic priming. It has beenreported that homographs embedded in sentencesfacilitate lexical decisions for related targets evenif these targets are related to meanings which aredifferent than those implied by the sentencecontext (e.g., Onifer & Swinney, 1981; Seidenberg,Tanenhaus, Leiman, & Bienkowski, 1982;Swinney, 1979; Tanenhaus, .Leiman, &Seidenberg, 1979). These results were interpretedas supporting an exhaustive, context-independentmodel of lexical access for homographs, accordingto which, all possible meanings of one homographare retrieved in parallel. An alternative view isthat contextual information affects lexicalprocessing of homographs at an early stage,

This work was supported by a grant awarded to the firstauthor by the Basic Research Foundation administered by theIsrael Academy of Science and Humanities, and by theNational Institute of Child Health and Human DevelopmentGrant HD-Ol994 to Haskins Laboratories. We are indebted toPazit Mey-Raz and Michal Kampf for their help in conductingthe experiments, and to Cyma Van Petten, Greg Simpson,Charles Perfetti, Keith Rayner, and three anonymousreviewers for their criticism on earlier drafts of this paper.

191

selecting only meanings which are contextuallyappropriate (e.g., Schvaneveldt, Meyer, & Becker,1976; Glucksberg, Kreuz, & Rho, 1986).

A third approach combines features of both previous views into an ordered access model. Thismodel posits exhaustive access which does not occur in parallel, but is determined by the relativefrequency of the two meanings related to the ambiguous word (e.g., Duffy, Morris, & Rayner, 1988;Forster & Bednall, 1976; Hogaboam & Perfetti,1975; Neil, Hilliard, & Cooper, 1988; Simpson,1981; and see Simpson, 1984, for a review).Hogaboam and Perfetti (1975) have demonstratedthat whatever the biasing context, the dominantmeaning of a homograph is retrieved first.Evidence for an ordered access was also presentedby Simpson (1981), who showed that in a nonbiasing context, only targets which were related to thedominant meaning of an ambiguous word, wereprimed. Similarly, differential activation of highand low-frequency meanings of ambiguous homographs was also demonstrated with event relatedpotentials (Van Petten & Kutas, 1987), and bymonitoring eye movements (Duffy et al., 1988;Rayner & Frazier, 1989).

If more than one meaning of a homograph canbe retrieved even if it appears in a biasingsentence context, multiple-meaning access should

192 Frost and Bentin

be the rule for homographs presented in isolation.This hypothesis was confirmed by Holley-Wilcoxand Blank (1980), who found that polysemousprimes (e.g., BANK) facilitated lexical decisions totargets related to all of their meanings. HolleyWilcox & Blank (1980) interpreted their results assupporting the parallel-access model. Morerecently however, Simpson and Burgess (1985)reported evidence for an ordered access model forisolated homographs. They have shown that in thecase of isolated homographs the most frequentlyused (dominant) meaning is accessed first, whilethe less frequently used (subordinate) meaning isaccessed relatively later.

Most studies of lexical ambiguity focused onhomophonic homographs (i.e., letter strings thathave a single pronunciation but two or moremeanings, e.g., BANK). However, homophonichomographs are not the only forms of wordambiguity. Ambiguity can exist also in therelationship between the orthographic and thephonologic forms of a word. For example, incontrast to "BANK," the printed letter string"WIND" has two different pronunciations, each ofwhich has a different meaning. In a recent study,Frost, Feldman, and Katz (1990) examined theeffect of phonological ambiguity in SerboCroatian. Subjects were presented simultaneouslywith printed and spoken words, and were requiredto determine whether they matched. Phonologicalambiguity was produced using letters whichrepresented different phonemes in the Cyrillic andRoman alphabets. The results showed thatmatching phonologically ambiguous printed wordswith their spoken realizations was delayedrelative to the matching of unambiguous printedpatterns in which only letters unique to onealphabet were used. This delay was significantlylarger when the ambiguous print was matchedwith the less frequent spoken alternatives thanwhen it was matched with the more frequentspoken alternative. Frost et al. (1990) suggestedthat these results support a multiple access modelin which dominant alternatives reach a higherlevel of activation. The effect of phonologicalambiguity was examined in English as well.Carpenter and Daneman (1981) havedemonstrated that the duration of eye fixations onheterophonic homographs was longer when thephonological alternative implied by the semanticcontext was a low-frequency word than when itwas a high frequency word. In a direct comparisonbetween heterophonic and homophonichomographs, Kroll and Schweickert (1978) foundthat heterophonic homographs like "wind" take

longer to name than homophonic homographs.These results suggest that in English, as in SerboCroatian, heterophonic homographs are processeddifferently than homophonic homographs.However, both in English and in Serbo-Croatianheterophonic homographs form a small andperhaps non-representative group of words.

The unvoweled Hebrew orthography presents anopportunity to examine the process of disambiguating the meaning of heterophonic homographs. In Hebrew, letters represent mostly consonants while vowels can optionally be superimposed on consonants as diacritical marks. In mostprinted material, (except for poetry, holy scriptures and children's literature), the vowel-marksare usually omitted. Since different vowels may beadded to the same string of consonants to formdifferent words, the Hebrew unvoweled print cannot specify a unique phonological unit. Therefore,a printed letter string is very frequently phonologically ambiguous, representing more than oneword, each with a different meaning.

In a previous study (Bentin & Frost, 1987) weexamined the influence of semantic and phonologic ambiguity on lexical decision and on namingisolated Hebrew words. We found that lexical decisions for unvoweled ambiguous consonantstrings were faster than for any of the high- orlow-frequency voweled (therefore disambiguated)meanings of the same strings. In contrast, namingambiguous unvoweled words was as fast as naming the high-frequency voweled alternative,whereas naming the low-frequency alternativewas significantly slower. On the basis of these andprevious results (Bentin, Bargai, & Katz, 1984),we suggested that lexical decisions for unvoweledHebrew words are generated prior to the processof phonological disambiguation, probably on thebasis of orthographic familiarity (cf. Balota &Chumbley, 1984; Chumbley & Balota, 1984,Seidenberg, 1985). This suggestion also accommodates previous data demonstrating that orthographic information is used for lexical decisionsand naming more extensively in Hebrew than inother languages (Frost, Katz, & Bentin, 1987).

In contrast to lexical decision, naming necessarily requires the selection of one phonological alternative of the ambiguous letter string. The significant delay in naming the low-frequency voweled alternative relative to the unvoweled and thehigh-frequency forms of the same letter string, ledus to support the ordered-access model for the retrieval of phonological information. Consequently,we suggested that, when confronted with phonologically ambiguous letter strings, readers retrieve

Processing Phonologial1 and Semantic Ambiguity: Evidence from SemiJntic Priming at Different SOAs 193

the high-frequency phonological structure first.The naming task, however, cannot disclose covertphonological selection processes. In particular,naming does not reveal whether phonological alternatives, other than the reader's final choice,had been accessed during the process of disambiguation. For example, in our previous study,subjects overtly expressed only one phonologicalstructure, more often the high-frequency alternative. However, we could not determine whether alternative words were generated but discarded during the output process, or whether only one wordwas generated from the print. Moreover, althougheach phonological form was related to a differentmeaning, naming does not necessarily imply access to semantic information. Therefore, althoughour previous results supported a frequency-ordered retrieval of phonological alternatives, amore direct measure was necessary to examinewhether more than one meaning of a heterophonichomograph is automatically activated, andwhether this access is ordered by the relative frequency of each meaning.

In the present paper we addressed this questionusing a semantic priming paradigm similar tothat used by Simpson and Burgess (1985).Isolated ambiguous consonant strings werepresented as primes and the targets were relatedto only one of their possible meanings. Weassumed that if a specific meaning of the prime isinitially accessed, lexical decision for targets thatare related to that meaning should be facilitated.

A second question addressed in the presentstudy refers to the time course of activation ofdominant and subordinate (i.e., high-and low-frequency) meanings of phonologically ambiguousletter strings. Several studies in English haveshown that in a sentence context, the subordinatemeaning is active only during a limited period oftime (Seidenberg et a1. 1982; Van Petten & Kutas,1987). Similar results were found also for isolatedhomographs (Kellas, Ferraro, & Simpson, 1988;Simpson & Burgess, 1985). In particular, Simpsonand Burgess (1985) found that an SOA of 16 msbetween prime and target was sufficient to facilitate lexical decisions for targets related to thedominant meaning, but not for targets related tothe subordinate meanings. Relatedness to thesubordinate meaning facilitated lexical decisionsonly when the SOA between prime and targetranged from 100 to 300 ms. The fast decay of thesubordinate meaning was explained in that study,by assuming that the limited capacity attentionsystem (Neely, 1977), must focus on only onemeaning, and in the absence of disambiguating

context, the dominant alternative is usually chosen (see also Kellas et al., 1988). However, since inHebrew, several phonological units are activatedin addition to several semantic nodes, it is possiblethat the activation of both dominant and subordinate alternatives lasts longer. This might happen,for example, if the retrieval of different phonological units results in more extensive lexical processing. In the present study we examined this possibility by manipulating the SOA between the ambiguous primes and the targets.

EXPERIMENT 1-AIn Experiment 1-a we presented subjects with

unvoweled heterophonic homographs as primes.Applying different vowel patterns, each primecould be read both as a high- and as a lowfrequency word. In each trial the prime wasfollowed by a word or by a nonword target at 100ms or 250 ms SOA Subjects were instructed toread the primes silently and to make lexicaldecisions to the targets. Across subjects, eachtarget was either unrelated to its prime, or relatedto the dominant or to the subordinate meaning ofthe ambiguous prime. Facilitation of lexicaldecisions in any related condition (relative to theunrelated condition) was considered evidence foraccessing the related meaning of the prime.

MethodSubjects. Forty undergraduate students, native

Hebrew speakers, participated in the experimentfor course credit or for payment.

Stimuli. The primes were 40 ambiguous consonant strings which represented both a high- and alow-frequency word. In the absence of a reliablefrequency count in Hebrew, we estimated thesubjective frequency of each word using the following procedure: From a pool of 100 ambiguous consonant strings we generated two lists of 100 voweled words each. Each list of disambiguated wordscontained only one form of the possible realizations of each homograph. Dominant and subordinate meanings were equally distributed betweenthe lists. Both lists were presented to 50 undergraduate students, who rated the frequency ofeach word on a 7-point scale from very infrequent(1) to very frequent (7). The rated frequencieswere averaged across all 50 judges. Each of the 40homographs that were selected for this study represented two words that differed in their ratedfrequency by at least 1 point on that scale. Thevalidity of this selection was then tested by naming: Twenty four subjects were presented with theunvoweled homographs, and their vocal responses


were recorded. We measured the relative dominance of each phonological altemative as reflectedby the number of times it was actually chosen andpronounced by the subjects. Only those homographs whose frequency judgments coincided withthe results obtained in the naming task (i.e., atleast 66% of the subjects chose to name the phonological altemative that had a higher frequencyrate), were used in the experiment.

Two targets were associated to each selectedhomograph. One target was semantically relatedto its dominant meaning, and the other to its subordinate meaning. The targets were all unambiguous (i.e., even without vowel marks they represented only one word). In order to ensure similar semantic relatedness for the dominant and thesubordinate meanings, the semantic relation ofprimes and targets was rated by the same 50judges on a 7-point scale, from unrelated (1) tohighly related (7). The means of those ratingswere 5.2 for the dominant meanings, and 5.3 forthe subordinate meanings. Each of the 80 targetswas also paired with an unrelated prime. The unrelated primes were 40 heterophonic homographsselected from the original pool and different thanthose used in the "related" conditions. Becausenone of their possible readings was related to thetargets, and because dominance is irrelevant inthe unrelated condition, the same prime precededthe targets used in the dominant and the subordinate related conditions. Hence, there were only 40different ambiguous primes in the unrelated conditions which were rotated across subjects. In ad-

dition to the word-word pairs, 80 word-nonwordspairs were introduced as fillers. The words wereheterophonic homographs different than thosecontained in the original pool. The nonwords wereconsonant strings that have no meaning inHebrew regardless of vowel configuration. An example of related and unrelated prime-target pairsis presented in Figure 1.

Design. There were eight experimental conditions: Different targets were related to the dominant or to the subordinate meanings of the ambiguous primes; each of the related targets wasalso presented in an unrelated condition. In eachof these four possible pairings, the SOA betweenprimes and targets was either 100 or 250 ms. Fourlists of words were formed: Each list contained 10prime-target pairs in each of the eight experimental conditions and 80 word-nonwords fillers. Theprime-target pairs were rotated across lists by aLatin Square design: related pairs in one list,were unrelated in another list, pairs whichappeared with a prime/target SOA of 100 ms inone list, appeared with SOA of 250 ms in anotherlist, etc. The purpose of this rotation was topresent the targets that were related to thedominant meanings of the primes and the targetsthat were related to the subordinate meanings ofthe primes, in both the related and the unrelatedconditions, at all SOAs, yet avoiding repetitionswithin a list. Hence, each target word served asits own control for the measurement of semanticfacilitation in an across-subjects design (seeFigure 1).

Unvoweled prime

Phonologicalalternatives

semanticmeaning

Dominant

MELACH

"salt"

MALACH

"sailor"

Condition

Prime

Target

Related

MLCH

"sugar"

Unrelated

KLV ("dog")

"sugar"

Related

MLCH

"ship"

Unrelated

KLV ("dog")

"ship"

Figure 1. Example of related and unrelated prime-target pairs in unvoweled Hebrew.

Processing PhonologiCtlI and Semantic Ambiguity: Eflidmce from Semantic Priming lit DiJfrrmt SOAs 195

Procedure and apparatus. The subjects weretested individually. They were instructed to readthe primes and to make lexical decisions only forthe targets by pressing a {"word" or a "nonword"response key. The dominant hand was alwaysused for "word" responses. All stimuli werepresented at the center of a Macintosh computerscreen (bold Hebrew font, size 24). The subjectssat approximately 70 cm from the screen, so thatthe stimuli subtended a horizontal visual angle of4 degrees on the average. A trial began with thepresentation of the prime which was replaced bythe target at the end of the respective SOA period.The target was continuously exposed until aresponse was recorded. The inter-stimulusinterval was 2500 ms from subject's response tothe onset of the following prime. Each sessionstarted with 16 practice trials. The 160 test trialswere presented in one block.

ResultsMeans and standard deviations of RTs for

correct responses were calculated for each subjectin each of the eight experimental conditions.Within each subject/condition combination, RTsthat were outside a range of 2 SDs from therespective mean were excluded, and the mean wasrecalculated. Outliers accounted for less then 5%of all responses. This procedure was repeated inall six experiments in the present study.

RTs and errors in the different experimentalconditions are presented in Table 1. Lexicaldecisions to targets related to the dominantmeanings of the ambiguous primes were fasterthan to unrelated targets, at both 100 and 250 msSOA. In contrast, lexical decisions to targetsrelated to the subordinate meanings were faster

than responses to unrelated targets only at 250ms SOA. At 100 ms SOA, lexical decisions torelated targets were apparently slower thanlexical decisions to unrelated targets.

The statistical significance of those diffl'-enceswas assessed by an analysis of variance (ANOVA)across subjects (F1) and across stimuli (F2), withthe main factors of semantic relatedness (related,unrelated), dominance of prime-meaning(dominant, subordinate), and SOA 000,250 ms).The main effects of relatedness, dominance, andSOA were significant: RTs to related targets werefaster than to unrelated targets [F1(1,39)=22.0,MSe=1789, p<.OOl; F2(1,39)=15.7, MSe=2655,p<.OOlJ; RTs to targets that referred to thedominant meaning of the prime in the relatedcondition were faster than RTs to targets thatreferred to the subordinate meaning of the prime[F1(l,39)=14.6, MSe=2373, p<.OOl; F2(1,39)=5.75,MSe=7509, p<0.02J; and RTs at 250 ms SOA werefaster than at 100 ms SOA [F1(1,39)=63.9,MSe=2315, p<.OOl; F20,39=27.0, MSe=5319,p<.OOlJ.l Relatedness interacted with dominance[F1(1,39)=5.62, MSe=2119, p<.OOl; F2(1,39)=3.16,MSe=3594, p<.08J, and with SOA [F1(1,39)=14.0,MSe=1256, p<.OOl; F2(1,39)=10.5, MSe=2332,p<.002J, The interaction of SOA and dominancewas not significant (F1, F2 <1.0). The three-wayinteraction was significant in the subject analysis[F10,39)=4.0, MSe=2191, p<.05J, but onlyapproached significance in the stimulus analysis[F2(1,39)=2.7, MSe=4868, p<0.10J. The three-wayinteraction seems to have resulted in part fromgreater RTs differences between SOAs forunrelated dominant primes (37 ms) than forunrelated subordinate primes (17 ms). We do nothave an explanation for this difference.

Table 1. Reaction times and (percentage of errors) to related and unrelated targets in the different experimentalconditions with phonologically ambiguous (unvoweled) primes (Experiments J-a and J-b).

Dominant Primes Subordinate Primes Nonwords

SOA 100 250 750 100 250 750 1-a 1-b

Unrelated 715 678 692 718 701 714 754 778(9%) (8%) (8%) (12%) (12%) (10%) (11%) (8%)

Related 684 639 658 739 669 692(10%) (7%) (8%) (10%) (13%) (11%)

PrimingErrect +31 +39 +34 -21 +32 +22


To elaborate the three-way interaction, andbecause we were concerned with the differentpatterns of facilitation for the dominant and thesubordinate meanings at the short and the longerSOAs, we conducted separate analyses of therelatedness and dominance effects at each SOA.These respective ANOYAs showed thatrelatedness interacted with dominance at 100 msSOA [F 1(1,39)=13.6, MSe=1502, p<.OOl;F2(l,39)=8.4, MSe=2905, p<.006],but not at 250ms BOA [Fl, F2 (1,39)<1.0). A Tukey-A post hocanalysis of the interaction at 100 ms SOArevealed that the difference between unrelatedtargets and targets related to the subordinatemeanings of the homographs was not significant,whereas, lexical decisions for targets related tothe dominant meaning of the homographs werefaster than to unrelated targets.

The differences in error rates between thevarious experimental conditions did not producesignificant effects.

EXPERIMENT l·BA more complete description of the time course

of activating the dominant and subordinatemeanings of heterophonic homographs requiredexamination of the semantic priming effects at anSOA longer than 250 ms. This condition could notbe included in the first part of the experiment because the total number of stimuli used in our rotated within-subjects design did not permit an additional division.2 Therefore, this condition wasexamined in a second group of 40 subjects sampled from the same population of undergraduatesas in Experiment 1-a.

The stimuli, design, and procedure were similarto those used in Experiment 1-a, except that theSOA between primes and targets was 750 ms. Tomake the structure of the stimulus lists as similaras possible to the previous experiment, weintroduced as fillers an identical number ofheterophonic homographs with a shorter SOA of250 ms. Moreover, because subjects encounteringonly long delays between primes and targetsmight actively invoke the two phonologicalternatives, whereas subjects encountering bothlong and short delays might not, a second purposeof the fillers with the shorter SOAs was to preventsubjects from developing this search strategy.

ResultsRTs were faster for related targets than for

unrelated targets, and for targets related to thedominant meaning of the prime than for targetsrelated to the subordinate meaning <Table 1). The

statistical significance was assessed in a two-wayanalysis of variance across subjects (Fl), andacross stimuli (F2). The main factors weresemantic relatedness (related, unrelated), anddominance of prime-meaning (dominant,subordinate). The ANOYA showed that both maineffects were significant: [Fl(1,39)=24.3,MSe=1286, p<O.OOl, and F2(1,39)=14.6,MSe=1765, p<O.OOl for semantic relatedness, andFl(1,39)=10.3, MSe=3123, p<0.002, andF2(1,39)=11.6, MSe=3378, p<0.002, for dominanceof the prime-meaning]. The interaction of the two

. factors was not significant [Fl, F2 (1,39)<1.0].Planned comparisons revealed that RTs to targetsrelated to the subordinate alternatives of theprime-meanings were significantly faster than inthe unrelated condition [t(1,39)=2.54, p<0.01]. Thepattern of semantic facilitation obtained for thefillers with 250 ms SOA was similar to the patternobtained with the identical SOA in Experiment 1a (33 ms facilitation for targets related to thedominant meaning, and 20 ms for targets relatedto the subordinate meanings).

DiscussionThe results of Experiments 1-a and 1-b suggest

that meanings of isolated heterophonic homographs were retrieved as predicted by an orderedaccess model. The meaning of the dominantphonological alternative was accessed faster thanthat of the subordinate phonological alternative.However, the time course of activating the subordinate meanings was different from that foundwith English homophonic homographs (Simpson &Burgess, 1985) in several ways. The subordinatemeanings in Simpson and Burgess's study havebeen already activated at 100 ms, and decayed af·ter 300 ms from stimulus onset. In contrast, themeanings of subordinate phonological alternativesin the present study was not available at 100 ms.

The subordinate alternatives were active at 250ms and, in contrast to English, they were stillavailable as late as 750 ms from stimulus onset.Hence, the present data suggest that subordinatemeanings of heterophonic homographs areaccessed slower than the subordinate meaning ofpolysemous words, but they remain active for alonger time.

The divergence between the time course of disambiguating Hebrew heterophonic homographsand English homophonic homographs might reflect language-related differences or, altematively,basic differences in processing heterophonic andhomophonic homographs. However, before goingany further in speculating about mechanisms of

Processing Plwnological and Semantic Ambiguity: EfJidenc:e from Semantic Priming at DiJfrrent SOAs 197

disambiguation of homographs, it was importantto make sure that the dominant and subordinateforms of the present stimuli were equivalent intheir efficiency to prime their respective targets.To control for differences in accessing dominantand subordinate meanings in absence of phonological ambiguity, and to understand better the independent relationship between the dominant andthe subordinate phonological altematives of oneletter string and their respective meanings, a second experiment was conducted. In the second experiment we examined the pattem of semantic facilitation of targets related to each meaning, whenthe phonological units to which they were relatedwere presented in a disambiguated form.

EXPERIMENTS 2-A AND 2-8The interpretation of the apparently ordered re

trieval of the subordinate and the dominant meanings of the phonologically ambiguous letter stringspresented in Experiments 1-a and 1-b was basedon the relative magnitude of priming effects. Thisinterpretation assumed that the observed difference between dominant and subordinate meaningsof the primes is accounted for by their phonological ambiguity. In other words, it was assumedthat in a disambiguated form, the subordinate andthe dominant primes would have primed their respective targets equally. The purpose ofExperiment 2 was to test this assumption.

Hebrew provides a unique opportunity tocompare semantic priming effects involvingaltemative meanings of homographs with thesemantic priming effects involving the same wordspresented explicitly, i.e., in a non-ambiguous form.In contrast to homophonic homographs that canbe disambiguated only by semantic context (for

example by embedding the homograph in asentence), Hebrew heterophonic homographs canbe disambiguated and still be presented asisolated words. This can be achieved by adding thediacritical dots to the ambiguous letter strings.The advantage of this procedure is that theexperimental structure and the primingconditions remain constant for the ambiguous andunambiguous presentations.

MethodSubjects. Eighty undergraduate students, all

native Hebrew speakers, participated for coursecredit or for payment. None of the subjectsparticipated in the previous experiments. As inthe previous experiments, 40 subjects were testedwith prime/target BOAs of 100 ms and 250 ms(Experiment 2-a), and the other 40 with 750 msBOA (Experiment 2-b).

Stimuli, design, and procedure. The stimuli,experimental design, and procedure were identicalto those used in Experiments 1-a and 1-b, exceptthat all the words and nonwords were presentedin conjunction with vowel marks. Thus, each wordwas presented in an unequivocal phonologicalform, and had only one meaning.

ResultsAt all BOAs and with both dominant and

subordinate primes, RTs to related targets werefaster than RTs to unrelated targets (Table 2).

The statistical significance of the priming effectsat 100 ms and 250 ms BOAs in Experiment 2-awas assessed by ANOVA across subjects (F1) andacross stimuli (F2). The main factors weresemantic relatedness (related, unrelated),dominance of prime (dominant, subordinate), andBOA (100 ms, 250 ms).

Table 2. Reaction times and (percentage of errors) to related and unrelated targets in the different experimentalconditions with phonolosically unambisuous (voweled) primes (Experiments 2-a and 2-b).


SOA 100 2SO 750 100 2SO 750 2·a 2-b

Unrelated 722 681 716 746 702 725 767 765(8%) (10%) (7%) (9%) (12%) (8%) (9%) 8%)

Related 690 634 672 703 664 683(8%) (8%) (8%) (8%) (8%) (6%)

PrimingEffect +32 +47 +44 +43 +38 +42


The ANOVA showed that across SOAs, RTs totargets in the related condition were faster thanin the unrelated condition £Fl(l,39)=68.8,MSe=1852, p<.OOl; F2(l,39)=55.5, MSe=2194,p<.OOll, RTs to targets related to dominantprimes were faster than to targets related to subordinate primes [Fl(1,39)=18.6, MSe=2013,p<.ool; F2(1,39)=6.3, MSe=5491, p<.Oll, and RTswere faster at 250 ms SOA than at 100 ms SOA[Fl(1,39)=37.9, MSe=4223, p<.ool; F2(1,39)=158,MSe=1123, p<.OOl]. However, in contrast toExperiment 1-a, none of the interactions were statistically significant (Fl, F2<1.0; for Relatednessby Frequency; (Fl<1.0, F2=1.3 for Relatedness bySOA; F 1, F2<1.0; for Frequency by SOA, andFl=1.2, F2=1.0, for the three-way interaction).

The analysis of the priming effects at 750 msSOA in Experiment 2-b, revealed a significanteffect of Semantic relatedness £Fl(l,39)=44.3,MSe=1689, p<.OOl, F2(1,39)=50.1, MSe=1539,p<.OOl), and no main effect of Frequency of theprime [F 1(1,39)=2.8, MSe=1432, p>.09;F2(1,39)=1.4, MSe=2692, p>.19). The interactionbetween the two factors was not significant (Fl,F2<1.0). The effects of semantic facilitationobtained with the fillers at 250 ms SOA inExperiment 2-b, were very similar to the effectsobtained with targets at the same SOA inExperiment 2-a (49 ms for targets related to thedominant alternatives, and 47 ms for targetsrelated to the subordinate alternatives).

DiscussionThe absence of an interaction between semantic

priming and the frequency of the prime revealedthat, in disambiguated form, the dominant andthe subordinate phonological alternatives of theheterophonic homographs were equally effectivein facilitating lexical decisions to related targets.In addition, the results of Experiments 2-a and 2-bshowed that the time course of processing highand low-frequency unambiguous Hebrew wordswas similar. Hence, Experiments 2-a and 2-b suggest that the difference in processing dominantand subordinate alternative meanings of heterophonic homographs observed in Experiments 1-aand 1-b was, indeed, caused by the ambiguous nature of the primes that were both phonologicallyand semantically equivocal.

Although the primes in Experiments 2-a and 2-bwere unambiguous, an effect of dominance wasobtained. Targets related to the dominantphonological alternatives incurred faster RTs thantargets related to the subordinate phonologicalalternatives. Because in Experiments 2-a and 2-b

the primes were unequivocal, this effect should beconsidered as a pseudodominance effect. Thisoutcome might have resulted from our design inwhich different targets followed identicalambiguous primes. Consequently, the comparisonacross dominant and subordinate categoriesinvolved different target words. It is possible thatthere were intrinsic decision time differencesbetween the target words, such that targets thathappened to be related to the dominantalternatives were accessed faster than targetsrelated to the subordinate alternatives. However,since the conclusions concerning semanticfacilitation depend on the interaction withinprime categories (comparing RTs to the sametarget in related vs. unrelated conditions), thepseudodominance effect has no theoreticalimportance.

In Experiments 3-a and 3-b we sought toexamine the possible sources of the differencesbetween the time course of activation found withEnglish homophonic homographs (e.g., Simpson &Burgess, 1985), and between our present resultswith Hebrew heterophonic homographs. Weendeavored to isolate the effects of semantic andphonologic ambiguity and to control for possiblelanguage specific factors. For this purpose, wehave used the design of Experiment 1 with a newset of stimuli. These were Hebrew homophonichomographs, i.e., words like "BANK,· that havetwo meanings but only one pronunciation.

EXPERIMENTS 3-A AND 3-DExperiments 3-a and 3-b examined the time

course of activation of dominant and subordinatemeanings of Hebrew homophonic homographs.Each stimulus was a pattern of letters representing only one word (one phonological unit); thatword, however, had two meanings, one more frequent than the other. Consequently, like mostEnglish homographs, these stimuli were semantically ambiguous but phonologically unequivocal.Using exactly the same design as in the previousexperiments, the present experiments allowedcomparison of homophonic and heterophonic homographs within one language - Hebrew.

MethodSubjects. The subjects were 120 undergraduates,

native Hebrew speakers. They participated in theexperiments for credits or payment. Sixty subjectsparticipated in Experiment 3-a, and 60participated in Experiment 3-b.

Stimuli. The primes were 36 ambiguoushomophonic homographs that were selected from

Processing Plwnological and Semtmtic Ambiguity: Evidencefrom Semantic Priming at Dilfrrent SOAs 199

a pool of 120 homographs. Each selected word hada dominant and a subordinate meaning.Dominance was determined empirically by thefollowing procedure: 50 subjects rated thefrequency of the meanings of all homographs on a7-point scale from very infrequent (1) to veryfrequent (7). Because naming could notdistinguish between meanings of homophonichomographs, the rated frequencies were validateddifferently than in Experiment 1. A group of 32subjects were read a list containing onlyhomophonic homographs, the meanings of whichwere rated at least 1 point apart on the frequencyscale. These words were read one at a time. Thesubjects responded verbally with their firstassociation to each word. The meaning that thesubjects had in mind was inferred from theirresponse. Dominant meanings were those thatwere produced by at least 66% of the subjects, andsubordinate meanings were those that were notproduced by more than 33% of the subjects. Eachprime was paired with two target words: One wassemantically related to the dominant meaning andthe other to the subordinate meaning. Thirty-sixadditional homophonic homographs from the samepool were used to form semantically unrelatedpairs. In addition to the word-word pairs, 72 wordnonwords pairs were again introduced as fillers.The words were homophonic homographs thatwere taken from the original pool. The 72nonwords were taken from Experiment 1-a.

Design and procedure. The design ofExperiments 3-a and 3-b was identical to that ofExperiments 1-a and 1-b. One group of 60 subjectswere tested using SOAs of 100 ms and 250 msbetween primes and targets. Fifteen subjects were

assigned to each offour lists, structured exactly asin Experiment 1-a (except that in each list therewere 9 targets rather than 10 in each condition).Across lists, each target appeared in both relatedand unrelated conditions, and at both SOAs.

The second group of 60 subjects was testedusing the same stimulus lists, with a designidentical to Experiment 1-b, that is with thelonger SOA (750 ms). Although separate analyseswere conducted in each group, we will report allthe results in one section.

Results and Discussion.The RTs in the related condition were faster

than in the unrelated condition at all SOAs, fordominant as well as for subordinate targets(Table 3).

Separate ANOVAs were conducted to assessedthe reliability of the priming effects acrosssubjects (F1) and across stimuli (F2), at 100 msand 250 ms SOAs (Experiment 3-a).These ANOVA showed that across SOAs, RTs totargets in the related condition were faster thanin the unrelated condition [F1(1,59)=19.7,MSe=1957, p<.OOl; F2(1,35)=15.6, MSe=1690,p<.OOll, RTs to targets related to dominantprimes were faster than to targets related tosubordinate primes [F1(1,59)=14.6 MSe=1675,p<.OOl; F2(1,35)=4.5 MSe=5166, p<.04l, and RTswere faster at 250 ms SOA than at 100 msSOA [F 1(1,59)=145. MSe=2035, p<.OOl;F2(1,35)=250. MSe=675, p<.OOl]. As withunambiguous primes in Experiments 2-a and 2-band in contrast to Experiments 1-a and 1-b,semantic relatedness did not reliably interact withany other factor.

Table 3. Reaction times and (percentage of errors) to related and unrelated targets in the different experimentalconditions with homophonic homographs as primes (Experiments 3-a and 3-b).


SOA 100 250 756 100 250 756 3-a 3-b

Unrelated 591 545 567 606 561 580 680 653(6%) (8%) (6%) (7%) (8%) (7%) (9%) (8%)

Related 580 522 553 588 540 570(6%) (6%) (6%) (6%) (8%) (8%)

PrimingEffed +11 +23 +14 +18 +21 +10


The analysis of the priming effects at 750 msSOA (Experiment 3-b), showed that the semanticrelatedness effect was reliable [F1(1,59)=7.9,MSe=1098, p<.007; F2(1,35)=7.6, MSe=694,p<.009] and RTs to targets were faster followingdominant primes than following subordinateprimes [F1(l,59}=10.6, MSe=1265, p<.002;F2(1,35}=3.9 MSe=3323, p<0.05]. As with theshorter SOAs, the interaction between the twofactors was not reliable (F1, ~<1.0).

The most important finding in Experiments 3-aand 3-b was that, in absence of phonologicalambiguity, both the dominant and the subordinatemeanings of Hebrew polysemous words werealready available at 100 ms from stimulus onset.Similarly to heterophonic homographs, theyremained active at least during the first 750 ms.These results suggest that the distinct pattern ofactivation observed for low- frequency phonological alternatives of heterophonic homographs (inExperiment 1-a) was caused by phonologicalrather than semantic ambiguity.

Because our study did not include a condition ofvery short SOA (16 ms) between primes andtargets, the onset of activating dominant andsubordinate meanings of Hebrew homophonichomographs cannot be directly compared to thepattern of activation reported by Simpson andBurgess (1985) with English materials. However,the persistent activation of subordinate meaningsat the longer SOA of 750 ms in the presentexperiment, clearly differs from the pattern ofactivation observed in English (Simpson &Burgess, 1985). This divergence suggests that theprocess of disambiguating polysemous wordsmight involve language-specific components.Possible interpretations of these results areelaborated in the general discussion.

Across experiments comparisonsSeveral formal comparisons were conducted to

assess priming effects involving heterophonicprimes at all SOAs (Experiments 1-a and 1-b) andpriming effects involving homophonic primes(Experiments 3-a and 3-b). For these analyses therelevant data from the four experiments werecombined in mixed ANOVA designs in which thetype of homographs was introduced as anadditional between-subjects factor. First, wecompared the pattern of semantic facilitation ofthe subordinate meanings only, across all SOAs,for the two types of homographs. The three-wayinteraction of relatedness, SOA, and homographtype was significant (F1(l,98}=6.9, MSe=1914,

p<0.009; F2(l,74}=3.6, MSe=2926, p<O.06),suggesting a reliable difference in the time courseof activating the subordinate meanings ofheterophonic and homophonic homographs.

Another finding regarding the two types ofhomographs was that the average effects ofsemantic priming of the dominant alternativesacross all SOAs, were twice as strong forheterophonic homographs (35 ms facilitation),than for homophonic homographs (16 msfacilitation). The statistical significance of thisdifference was assessed by a mixed ANOVAdesign in which RTs to the dominant meanings ofheterophonic homographs at all three SOAs, werecompared with the respective RTs to the dominantmeanings of homophonic homographs. The type ofhomography served again as a between subjectsfactor. This analysis revealed a significantinteraction of relatedness and homography type(F1(l,98)= 7.6, MSe=1675, p<0.007; ~(1,74}=6.0,MSe=1994, p<0.02). Whether the shrinking of thepriming effect for homophonic homographsrelative to heterophonic homographs reflectsprimarily differences in processing the two typesof homographs, or merely a floor effect due tomuch faster responses to homophonic thanheterophonic homographs, was not clear.Therefore, we replicated Experiment 1-a using anidentical number of subjects and identicalmethods.

The purpose of replicating Experiment 1-a was,in fact, two-fold. First, because the comparison ofheterophonic and homophonic homographs wasbased on a different pool of subjects, and becausethe most important difference relied on one datapoint, we aimed at reexamining the absence ofpriming effect (or the possible inhibition) forheterophonic homographs at 100 ms SOA Second,to examine whether the larger priming effectsfound for heterophonic relatively to homophonichomographs were due to an incidental overallslower performance of the subjects sampled inExperiment 1-a.

The results of this replication are presented inTable 4. As in the original experiment, lexical decisions for targets related to the subordinatemeanings of the primes were not facilitated at 100ms SOA. In addition, the nonsignificant trend ofinhibition observed in this condition inExperiment 1-a proved to be unreliable. Overall,the RTs in the replication were faster than theoriginal experiment. This suggests that the subjects employed in Experiment 1-a were generallyslower than all other subjects in this study.

Processing Phonological and Semantic Ambiguity: Evidence from 5enulntic Priming at Dijfrrent SOAs 201

Table 4. Reaction times and (percentage oferrors) to related and unrelated targets in the replication ofExperimentsI-a.

Dominant Primes Subordinate Primes

SOA 100 250 100 250

Unrelated 626 588 635 609(9%) (10%) (13%) (11%)

Related 601 557 635 588(8%) (5%) (10%) (10%)

PrimingEffect +25 +31 0 +21

Nonwords

677(8%)

Nevertheless, the pattern of the semantic facilitation with unvoweled ambiguous heterophonic homographs was replicated. The statistical significance of the priming effects was assessed byANOVA across subjects (F1) and across stimuli(F2). The main effects of relatedness and dominance were significant [F1(1,39)=4.6, MSe=1436,p<0.04; F2(1,39)=5.0, MSe=1834, p<0.03;F1(1,39)= 12.6, MSe=1552, p<0.001; F2 (1,39)=9.9, MSe=2648, p<0.OO3; respectivelyl. The twoway interaction did not reach significance in thestimuli analysis [F1(1,39)=3.6, MSe=1741, p<0.06;F2(1,39)=2.4, MSe=1756, p<0.1l. Planned comparisons revealed that RTs to targets related to thesubordinate alternatives of the prime-meanings at250 ms SOA were significantly faster than RTs totargets in the unrelated condition [t(1,39)=3.1,p<0.OO4l. We will refer to the additional implications of this replication in the General Discussion.

GENERAL DISCUSSIONIn the present study we examined the process of

disambiguating Hebrew heterophonic and homophonic homographs presented in the absence ofbiasing context. To summarize the results of ourinvestigation, it appears that regardless of relativedominance, at least two different meanings ofeach homograph were retrieved. However, thetime-course of activating the different meaningsand possibly the amount of activation were influenced by phonological factors. With homophonichomographs, subordinate as well as the dominantmeanings were active as early as 100 ms fromstimulus onset. On the other hand, with heterophonic homographs, only the dominant meaningwas available at 100 ms SOA, whereas the availability of the subordinate meaning was delayed.In contrast to the differences found at the onset of

meaning activation, the decay of activation of subordinate meanings of homophonic and heterophonic homographs was similar; they all remainedactive as late as 750 ms from stimulus onset.Thus, the onset activation pattern of Hebrew heterophonic homographs observed in the presentstudy is in agreement with the ordered-accessmodel suggested by Simpson and Burgess, (1985).At present this conclusion must be limited to heterophonic homographs because unlike Simpsonand Burgess (1985), we did not use SOAs shorterthan 100 ms. Our findings suggest then, that heterophonic homographs and homophonic homographs are disambiguated differently. This difference and the long lasting activation of subordinatemeanings of Hebrew but not English homographs,may provide some insights regarding the lexicalstructure and the process of word identification.

The lexical representation of homophonichomographs is controversial. Some authors assertthat homophonic homographs entertain differentlexical entries, one for each meaning (Forster &Bednall, 1976; Jastrembski, 1981; Kellas et aI.,1988). Other authors claim that a homograph hasonly one lexical entry, related to multiple nodes ina semantic network (Seidenberg et aI., 1982;Cottrell & Small, 1983). On the other hand,heterophonic homographs are, by definition,represented by several phonological units in thelexicon. Thus, phonologically ambiguous letterstrings refer to different lexical entries, one foreach phonological realization. The relativelydelayed access to the subordinate meanings ofheterophonic homographs, as compared withsubordinate meanings of homophonic homographscould be more easily accounted for by assumingonly one lexical entry for homophonic homographsand several entries for heterophonic homographs.3


According to such a model, the alternative lexicalentries are automatically activated by the uniqueorthographical pattern, though at different onsettimes. The present data and the results of ourprevious studies (e.g., Bentin & Frost, 1897)indicate that, in the absence of biasing context theorder of activation is determined by the relativeword frequency; higher-frequency words areaccessed before lower frequency words. As aconsequence of the multiple entries structure andthe ordered-access process, heterophonichomographs are phonologically disambiguatedbefore the semantic network is accessed. Eachactivated word (in the lexicon) is unequivocallyrelated to a meaning. Because entries of dominantwords are accessed before those of subordinatewords, the origin of the dominance effect on thetime course of activating the meanings of aheterophonic homograph could have been the welldocumented frequency effect on lexical access.

This interpretation may also account for theoverall greater priming effects found forheterophonic than for homophonic homographs. Itmight suggests that when one lexical unitactivates two or more semantic nodes, each ofthese nodes is activated less than nodes which areunequivocally related to phonological units in thelexicon. If, in contrast to heterophonichomographs, homophonic homographs wererepresented by only one lexical entry which isrelated to several semantic nodes, the process ofdisambiguating the different meanings shouldhave been less affected by the relative frequency(dominance) of using each meaning. Ourhypothesis is that activating a lexical entry in anunbiased semantic context, should automaticallyinitiate the retrieval of all its related meanings.Because only one lexical entry is active therelative dominance of the alternative meanings isirrelevant at the stage of lexical access. Relativefrequency factors might affect the order of theirretrieval at later processing stages, but our resultssuggest that, at least for the SOAs that have beenexamined in the present study, such an effect wasnot observed.

One caveat that must be considered whileinterpreting the difference in the amount ofpriming with homophonic vs. heterophonichomographs is that the former were overall fasterthan the latter. The reduction in overall RTslatencies in the replication of Experiment 1-arelative to the original experiment, and thecomparison of the nonword data across allexperiments help to clarify this issue. Because theRTs to nonwords in the replication were identical

to those in Experiment 3-a, we can assume thatthese two groups of subjects were comparable inoverall speed ofperformance. Nevertheless, RTs totargets related to heterophonic homographs wereslower by about 40 ms than RTs to targets relatedto homophonic homographs. This difference wasnot entirely unexpected; it conforms with previousfinding in Hebrew showing faster RTs forphonological unequivocal words than forphonologically ambiguous words (Bentin et a1.1984). However, this pattern might have caused afloor effect in the RTs to homophonic homographs

- that attenuated the absolute magnitude of thepriming effect. A floor effect as a sole explanationfor this attenuation is not entirely supported bythe data. Note, that although the overalldifference in RTs in the two homographicconditions was reduced by a factor of 3 (from 120to 40 ms) when the replication rather than theoriginal Experiment was considered, therespective reduction of the priming effect for thedominant alternatives was relatively small (from35 ms to 28 ms). Second, the smallest effect ofsemantic facilitation for homophonic homographs(11 ms) was obtained for dominant primes at 100ms SOA that were slower by 50 ms than theprimes at 250 ms SOA (which revealed a muchlarger facilitation). Thus, the observed differencein the magnitude of the priming effects betweenhomophonic and heterophonic homographs isconsistent with the hypothesis that they havedifferent lexical structures.

In addition to the implications on the lexicalstructure, our data are also relevant to argumentsregarding the use of phonology in wordidentification. One class of models suggest that(with the possible exception of very infrequentwords), printed words activate orthographic unitsthat are directly related to meanings in semanticmemory (e.g., Seidenberg, 1985; Seidenberg,Waters, Barnes, & Tanenhaus, 1984). Such amechanism had been invoked to explain, forexample, how homophones such as SALE andSAIL are correctly understood, or how patientswith acquired dyslexia can understand writtenwords without being able to read them aloud (Kay& Patterson, 1985).

An alternative class of models asserts that, mostof the time, access to meaning is mediated byphonology (e.g., Perfetti, Bell, & Delaney, 1988;Van Orden, Johnston, & Hale, 1988). The latterclass of models is supported by theoreticalconsiderations such as the parsimony of havingonly one mechanism that mediates access tomeaning for both speech and reading (e.g.,

Processing Phonological and Semantic Ambiguity: Evidence from Semantic Priming at Diffrrent SOAs 203

Liberman & Mattingly, 1989), and by evidencethat when the ability to derive phonology fromprint is poor (as in deep dyslexia), semantic errorsin reading are abundant (see for a reviewMarshall & Newcombe, 1980). Moreover, when thedirect connection from orthography to meaning isimpaired (as in some patients with surfacedyslexia), the meaning of printed words can beretrieved by pre-lexical application of graphemeto-phoneme (GTP) transformation rules(Coltheart, Masterson, Byng, Prior, & Riddoch,1983; Marshall & Newcombe, 1973).

As we have pointed out in previous papers, lexical decisions for unvoweled Hebrew words arebased primarily on orthographic codes (Bentin etaI., 1984; Bentin & Frost, 1987), and even fornaming, prelexical word phonology is not usuallyused by skilled readers (Frost et aI., 1987).Nevertheless, the present results suggest that, incontrast to lexical decisions, the retrieval of meaning requires the activation of the phonologicalstructure to which the printed word refers. Ifmeaning were retrieved directly from the orthographic input, no difference should have beenfound between processing homophonic and heterophonic homographs. The delayed onset of activating the meanings of the subordinate phonological altematives relative to the subordinate meanings of homophonic homographs, and possibly theoverall more robust priming effects observed whenthe primes were phonologically ambiguous thanwhen they were homophonic homographs, suggests that the former involved phonological disambiguation prior to the disambiguation ofmeaning.

One of the most intriguing results of the presentstudy was that subordinate meanings of both heterophonic and homophonic homographs were stillavailable and used 750 ms from stimulus onset.This result contrasts with the relatively fast decayof subordinate meanings of English homographs(Simpson & Burgess, 1985; Kellas et aI., 1988).Because the decay pattern was similar for bothtypes of Hebrew homographs, the divergence fromEnglish should be probably accounted for by language-related factors. One possible source of thedifferent results obtained in Hebrew and inEnglish may be related to the homographic characteristics of the Hebrew orthography. Hebrew,like other Semitic languages, is based on wordfamilies derived from tri-consonant roots. The rootis contained in all of its derivations, therefore,Hebrew contains many homophonic and heterophonic homographs. The wide spread of homography might have shaped the reader's reading

strategies. Because ambiguity is so prevalent inreading, the process of semantic and phonologicdisambiguation is governed mainly by context. Asthe disambiguating context often follows ratherthan precedes the ambiguous homographs, themost efficient strategy of processing them shouldconsist of maintaining their phonologic or semantic alternatives in working memory until the context selects the appropriate one. Note that by thisinterpretation the subordinate alternatives do notdecay automatically, but remain in memory untildisambiguation by context has occurred. However,a complete account of the specific characteristicsof the Hebrew orthography which might have influenced our results with homophonic and heterophonic homographs deserves further investigation.

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FOOTNOTES·]ournlll of Experimentlll Psychology: LeIIrning, Memory, lind

Cognition, 18, 58-68.tDepartment of Psychology, The Hebrew University, Jerusalem.lSimpson and BurgelS (1985) found no difference in RTs betweenSOAs of 100 and 300 ms. However, throughout the presentstudy, the main effect of SOA was quite reliable and robust(including in the replication of Experiment I-a), suggesting thatunlike S and B, in the present study the 100 ms SOA conditionwas more difficult than the other SOA conditions. A possibleexplanation of this difference is that our procedure did notinclude an initial fixation point

2Although phonologiC ambiguity is very common in the Hebreworthography, the set of stimuli used in the experiments wasconstrained by many experimental controls such as mean ratedfrequencies, dominance as reflected by naming performance,syntactic classes, rated semantic relatedness, etc. This set ofstimuli did not permit a within-subject design across all SOAs. Asimilar problem was raised and solved similarly by Simpson andBurgelllS (1985).

3Seidenberg et al. (1982) present a similar kind of single vs.multiple argument for noun-noun vs. noun-verb homophonichomographs, but they draw slightly different inferences. Theyargue that noun-verb homographs (e.g., train) have differententries in the lexicon and, hence, both meanings are alwaysaccessed for such words even when a strong priming word ispn!sented in the context. In contrast, for noun-noun ambiguities(e.g., boxer) there is only one entry in the lexicon, and meaningsare accelllSed in order of relative activation levels.

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Processing Phonological and Semantic Ambiguity - Haskins