Seeing through issues of semantic transparency - CiteSeerX

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Everything is Psycholinguistics: Material and Methodological Considerations in the Study of Compound Processing GARY LIBBEN University of Alberta

The specific domain that I discuss in this paper is the processing of compound words. This research area is no more than 30 years old and my own involvement in it has been for about half that time. The study of how compound words are processed is a very specific sub-field, considerably narrower than the domains of which we would normally consider. Yet, for a variety of reasons which I discuss below, compound processing research finds itself associated with issues that are central to our views of the fundamental nature of lexical processing, and the enterprise of psycholinguistic research itself. These are certainly the domains of which we do want to take stock. My goal in this article is to address issues that are of general interest through the medium of research on the representation and processing of compound words. In considering the development, current state, and likely future trajectory of a specific research domain, this provides us with an opportunity to gain a broader perspective on the field as a whole and to step outside (and hopefully above) the normal course of research activity.

This research reported here was supported by a Major Collaborative Research Initiative Grant from the Social Sciences and Humanities Research Council of Canada (SSHRC) to Gary Libben (Director), Gonia Jarema, Eva Kehayia, Bruce Derwing, and Lori Buchanan.

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I begin by considering the role that the construct of “morpheme” plays in lexical processing. Various kinds of evidence indicate that compound words are parsed into morphemes during processing, so that the mental lexicon can be said to have morphological representations (section 1). The finding that morphological parsing automatically activates all possible constituents challenges the traditional distinction between semantically transparent versus semantically opaque compounds (section 2). This in turn leads to a reappraisal of standard experimental techniques (section 3). Thus, the apparently parochial concerns that arise in the course of investigating the processing of compound words turn out to have dramatic consequences for what we take to be our object of study, and how we study it.

1. WHY ARE PSYCHOLINGUISTS INTERESTED IN COMPOUND WORDS? Compounds words are, by definition, multi-morphemic. As such they have a dual life: we can consider the meaning of the compound word as a whole (“whole-word meaning”) or we can examine the meanings of the constituent parts of the compound (“constituent meaning”). Evidence from aphasia indicates that speakers manipulate both types of meanings (section 1.1), and this in turn has implications for the interplay between lexical storage and morphological computation (section 1.2). Of particular interest are semantically opaque compounds, whose whole-word meanings are incompatible with their constituent parts (section 1.3).

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1.1. Whole word versus constituent meanings: A case study from aphasia In Libben (1993, 1998), I discussed the case of a patient, RS, who had become aphasic after suffering a brain hemorrhage in the temporoparietal area of the left hemisphere. In a paraphrase task, RS was asked to provide meanings for a set of compound words that included items such as butterfly, yellowbelly, and dumbbell. These items can be described as semantically opaque because the meanings of the whole words are not aligned in a straightforward manner with the meanings of their constituent morphemes. RS’s paraphrase patterns for these words were striking, and are given in (1). (1)

RS’S PARAPHRASES FOR SOME COMPOUND WORDS

COMPOUND WORD

RS’S PARAPHRASE

butterfly yellowbelly dumbbell

“a pretty fly…it’s yellow” “a yellow stomach…a chicken” “stupid weights” (followed by a reference to Arnold Schwarzenegger)

In all these cases, it seemed clear that RS was accessing the whole-word meanings of the compounds. For non-entomologists, most flies are not pretty, but butterflies are. Only chicken, meaning coward, refers to the meaning of yellowbelly as a whole, not to the colour of a stomach. Only dumbbells, but not other types of bells, are types of “weights”. However, in addition to this demonstrated access to the whole-word meanings of opaque compounds, RS’s paraphrases also seemed to show access to the independent meanings of constituents. The association of “yellow” with butterfly seems independently related to the colour of butter. The association of “stomach” to yellowbelly is clearly related to the independent meaning of belly. Finally, the association of “stupid” to dumbbell seems also to indicate independent access to constituent meaning. (As for the

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reference to Arnold Schwarzenegger, I leave it to the reader to decide whether this reflects activation of whole-word or constituent meaning.) The result of this blending of whole-word and constituent meanings had a negative effect on RS’s lexical comprehension, and to that extent her lexical processing was clearly impaired. But what was not at all clear was whether the processes that she was employing in lexical access were qualitatively different from the processes that nonimpaired native speakers of English employ in the everyday processing of such words. Is it possible, for example, that the processing of compounds always involves automatic and obligatory access to both whole-word and constituent meanings in a relatively independent manner? If this were the case, it would suggest that RS’s problem was not that she created multiple incompatible representations, but rather that she simply did not resolve the conflict that they created, as non-impaired language users do.

1.2 The trade-off between storage and computation The possibility that lexical processing involves automatic and obligatory online morphological parsing is what has drawn psycholinguists to the study of how multimorphemic words, and compound words in particular, are processed. It should be mentioned at the outset that this new attention to multi-morphemic word processing comes at a methodological price. The current techniques of investigation in lexical processing are extremely sensitive to a great number of variables that need to be controlled in the design of experiments. Because multi-morphemic words are, by definition, more complex than monomorphemic words, they present new challenges to

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experimental control, and accordingly make the design and analysis of experiments more difficult. Despite these methodological challenges, the study of multi-morphemic words opens up opportunities that cannot be ignored. First among these is the opportunity to understand the cognitive trade-offs that exist between lexical storage and morphological computation. Languages do not participate equally in the use of word-formation morphology. Those languages that do make extensive use of derivation and compounding derive benefit in terms of the language’s root inventory size because new words can be created without having to create new morphemes. Many psycholinguists who investigate the processing of multi-morphemic words ask whether morphological processing yields a similar benefit by obviating the need for all multi-morphemic words to have individual representations in the mental lexicon. Issues surrounding this question have received extensive attention, most notably in the domain of inflectional morphology (Pinker 1999; Pinker and Ullman 2002). The potential contribution of research on compound processing lies in its rather unique position at the crossroads of storage and computation (Libben 2006). On the one hand, there seems to be a way in which morphological parsing must occur for compounds. It is an extremely productive word-formation process in English, and even more so in related languages such as German. Thus, it is quite likely in both these languages that native speakers encounter novel compounds on a daily basis. Indeed, even when compounds are not novel in the language, they are quite likely to be novel to individual language users because of their low overall frequency of occurrence. As an illustration of this, consider the 1,437 noun-noun compounds which are currently listed in the English CELEX database (Baayen et al. 1993). Over half of these (836) have a

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written frequency of less than one in a million and only 35 have a frequency of over ten in a million. By contrast, words such as dog and cat have frequencies of roughly 75 and 25 in a million, respectively. To the extent that speakers of a language can interpret novel compound structures, they do so through the isolation and interpretation of constituent morphemes. This is not to say that their interpretations are guaranteed, or even likely, to be correct. The vast majority of compound words cannot be understood solely on the basis of their constituent morphemes. Inasmuch as members of a language community share particular meanings for compound words—rather than possible meanings for those words—storage is required. Seen in this perspective, compound words are rather unique structures in that they seem to require a morphological parsing strategy that is always on, as well as whole-word representations that are always available. Understanding how these features interact has been the focus of my research.

1.3. The significance of semantically opaque compounds Semantically opaque words offer an excellent opportunity to enhance our understanding of the interplay between storage and morphological computation. These are words for which morphological processing will yield results that are incompatible with whole-word meanings. This means that, if retained, the whole-word meanings would generate false comprehensions of the kind that were characteristic of RS’s paraphrases discussed above. It is of psycholinguistic interest to note that semantically opaque compounds are not

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nearly as exotic as we might think. While we might be somewhat puzzled by the possible referents for uncommon fruit and vegetable terms such as stonefruit, hackberry, cowpea, and plumapple, the semantic opacity of well-known fruit and vegetable compounds such as grapefruit, strawberry, chickpea, and pineapple scarcely gets noticed. The question of whether such words throw the lexical processing system into some degree of momentary disarray has been the subject of considerable research. As a final example of the phenomena that make compound processing interesting psycholinguistically and reveal the nature of morphological processing, let us return to the uncommon fruit and vegetable terms stonefruit, hackberry, cowpea, and plumapple. While most native speakers would not know what these words mean, very few would have difficulty parsing them into their constituents: stone+fruit, hack+berry, cow+pea, and plum+apple. A good deal of the research that I have been involved in over the past years has been focused on trying to determine how this online morphological parsing in reading is actually accomplished. Compound words present a much greater challenge to online morphological parsing than do affixed words. The difference is that affixes comprise a closed-class set in the language, so that morphological parsing can be accomplished by stripping affixes from their stems, as originally suggested by Taft and Forster (1975). Compound words, on the other hand, are formed, for the most part, from members of open-class sets. Thus, there are no reliable heuristics that can be employed to ensure that morpheme boundaries are correctly determined for stone+fruit, hack+berry, cow+pea, and plum+apple. Yet, native speakers of English do this easily and

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automatically, while not over-parsing words such as carpet and barking into car+pet or bar+king.

2. THE HUNGRY LEXICON Together with students and colleagues, I have had the opportunity to conduct experimental investigations on aspects of compound processing in Chinese, Dutch, English, French, German, Hebrew, and Japanese. What I would like to draw attention to is the general conclusion that emerges from this research, namely that the morphological processing system is not designed to get the right answer. It is not organized to generate exactly the correct morphological parse, nor is it organized to generate exactly the correct lexical excitation. Rather, it is designed to make the greatest number of potentially useful representations and analyses available to other components of the cognitive system: in this sense then, the lexicon may be said to be hungry. The robustness of compound processing is perhaps most clearly illustrated by looking at how novel compounds are parsed (section 2.1), which has led us to re-assess our understanding of how semantic transparency facilitates word recognition (sections 2.2 and 2.3).

2.1. Ambiguous novel compounds The first clue that morphological parsing is opportunistic arose from a set of studies that employed a rather unusual set of stimuli (Libben 1994; Libben et al. 1999). These stimuli can most appropriately be described as ambiguous novel compounds. They are words such as clamprod, seathorn, and cartrifle, which were constructed so that they could be

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parsed in two ways. In the case of clamprod, for example, the two parses would be clam+prod and clamp+rod. The initial purpose for the construction of these stimuli was to understand the properties of the putative morphological parser. I reasoned that if morphological parsing proceeds in a beginning-to-end manner, searching for morphemic representations along the way, ambiguous novel compounds such as clamprod would all be parsed with a morpheme boundary at the first opportunity (i.e., as clam+prod), generating a first possible parse. If on the other hand, the parser proceeded in a beginning-to-end manner until the largest lexical unit could be created, then the structures would most likely be given a last possible parse (i.e., as clamp+rod). In an initial experiment, participants were provided with a list of novel compound stimuli in which these special items were embedded. They were asked to read them aloud as clearly and carefully as possible, so that their speech could be used as materials for learners of English as a second language. This clear and careful speech created identifiable pauses at morpheme boundaries, and the location of these pauses was recorded as the dependent variable in the experiment. The results of the experiment revealed that digraphs such as the th in seathorn substantially constrained parsing choices. In contrast to this, for words without digraphs, results favoured neither the first possible parse nor the last possible parse alternatives. Most importantly, parsing choices were correlated with the semantic plausibility of alternative parses so that a string such as cardriver would be parsed as car+driver, but a string such as cartrifle, would be parsed as cart+rifle. The fact that both these strings

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begin with the possible initial morpheme car suggests that the choices were not driven by initial-constituent frequency, but rather by the semantic fit between constituents. The fact that semantic plausibility turned out to be the driving factor in parsing choices led to an important paradox. How could the relative semantic plausibility of the alternative parses drive the choice of morphological parse, when the calculation of such plausibility would require that the activation of constituents had already occurred? It seemed that the only possible resolution of this paradox would require that at the time of parsing choice—when participants had read the words aloud clearly and carefully—both alternative parses had been completed, and the semantically more plausible one was selected. This conclusion was counter-intuitive given the fact that during debriefing, when queried, only one of the 30 experiment participants indicated that she had noticed that some of the stimuli could be read in two ways. If ambiguous novel compounds were in fact receiving both parses automatically, they should take longer to process than matched non-ambiguous strings: for example, clamprod (consistent with either clam+prod or clamp+rod) should take longer to process than prodclam (consistent only with prod+clam). This prediction, which was tested in a follow-up experiment, turned out to be correct. In a lexical decision experiment, 30 participants were shown real compounds and novel compounds in the centre of a computer screen and were asked to judge as quickly as possible whether the stimuli were real words of English by pressing either a “yes” or a “no” key. It took participants significantly longer to reject the ambiguous novel compounds than to reject the unambiguous ones. The effect size was large, with

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unambiguous stimuli showing mean rejection times of 538 milliseconds and the ambiguous stimuli showing rejection latencies of 670 milliseconds—over 130 milliseconds slower. Interestingly, the ambiguous novel compounds that contained digraphs, such as seathorn, showed rejection latencies (661 milliseconds) that were only nine milliseconds faster than those for the orthographically unconstrained ambiguous novel compounds such as clamprod. This suggests that although the presence of digraphs affected the choice of competing parses, it did not constrain initial activation of alternative constituents. In a subsequent series of experiments Libben et al. (1999) explored these stimuli further in a primed recall task. It was found that seeing an ambiguous novel compound facilitated recall of semantic associates of all four of the possible constituent morphemes. Taking clamprod again as our example, the presentation of the string facilitated recall of sea (a semantic associate of clam), hold (a semantic associate of clamp), push (a semantic associate of prod), and stick (a semantic associate of rod). It seemed clear from these results that morphological parsing had automatically activated all possible constituents. These findings led us to conclude that “the lexicon is hungry”.

2.2. The semantic transparency of compound constituents What consequences does this view of a hungry lexicon have for the processing of existing compounds, particularly those that are semantically opaque? If the findings from novel word processing generalize to the processing of real words—if those words also undergo automatic and obligatory morphological processing—then semantically opaque

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compounds should be more difficult to process than semantically transparent ones. This is because the morphological parser would activate constituent representations that are incongruent with whole word representations. We began by building on the work of Sandra (1990) who, in his investigation of the effects of semantic transparency in Dutch, had found that semantically transparent compounds facilitate recognition of semantic associates of their constituent morphemes. Thus, Sandra (1990) found that words such as suntan facilitated (or primed) the recognition of moon, which is a semantic associate of the initial compound constituent sun, but not of the whole word. Would the same effect occur for semantically opaque compounds such as Sunday? Sandra (1990) found that it did not, and concluded that in contrast to semantically transparent compounds, semantically opaque compounds do not undergo morphological parsing (also called prelexical morphological decomposition). This conclusion, while perfectly consistent with the data, generated the same paradox we had noted in our study of ambiguous novel compounds. How could the cognitive system know whether a compound was transparent or opaque unless it had processed it in the first place? We embarked upon a series of studies (Libben et al. 2003) in which we explored the relationship between whole words and constituents among four types of compounds, given in (2). (2)

RELATIONSHIP BETWEEN WHOLE WORDS AND CONSTITUENTS IN COMPOUNDS

EXAMPLE

RELATIONSHIP

ABBREVIATION

car-wash strawberry jailbird hogwash

transparent-transparent opaque-transparent transparent-opaque opaque-opaque

TT OT TO OO

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In one experiment, the relationship between whole words and constituents for such compound words was investigated through a constituent priming paradigm. Eighty-seven participants first saw a compound constituent displayed on a computer screen for 500 milliseconds and then were shown the entire compound. The dependent variable was the lexical decision response time for the target compound words. As show in Figure 1, the general pattern of results suggested that both opaque and transparent compound words receive roughly equivalent facilitation from prior presentation of their constituent morphemes. Prior presentation of wash facilitated hogwash in much the same way that wash facilitated carwash. On average, compounds with transparent heads were responded

Response time (ms)

to more quickly than opaque heads, indicating the latter require extra processing.

900 875 850 825 800 775

TT OT TO OO

750 725 700 675 650 625 600 Unprimed

Constituent 1 Constituent 2 prime prime

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Figure 1: Patterns of constituent priming for transparent-transparent (TT), opaquetransparent (OT), transparent-opaque (TO), and opaque-opaque (OO) compounds found by Libben et al. (2003) (Experiment 2).

In Libben (1998), I proposed a model that might account for this apparent inconsistency by appealing to a distinction among levels. In this model, both opaque and transparent compounds undergo morphological parsing. They have identical lexical representations (shown in the middle level of Figure 2), but they differ with respect to how they are linked to the representations of their constituent morphemes at the conceptual level. In Figure 2, lines show associations between representations. TT, OT, and TO compounds are distinguished from each other in terms of how the conceptual level maps onto the lexical level. For example, with TT compounds, since both members of the compound are transparent, both the first and second term of the compound map from the conceptual level to the lexical level. This contrasts with OT and TO compounds, where only the transparent term is mapped from the conceptual level to the lexical level. The model also distinguishes between componential and non-componential compounds. The latter may have transparent associations between the meanings of the constituents in the compound and their meanings as free morphemes, but cannot be understood in terms of normal head-modifier relations. The exocentric compound bighorn would be an example of this type, as it is a type of sheep rather than a type of horn. Square brackets show structured representations, and componential versus noncomponential compounds are distinguished in terms of whether there are structured or

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not at the conceptual level. For example, the TT-componential compound [blue][berry] has internal structure at the conceptual level, while the TT-non-componential compound bighorn does not.

Conceptual level

blue [blue][berry] berry

big

Lexical level

blue - [blue][berry] - berry

big - [big][horn] - horn

blueberry

bighorn

Stimulus level

TT-componential

bighorn

horn

TT-noncomponential

Conceptual level

straw [straw][berry] berry

yellow

Lexical level

straw - straw][berry] - berry

yellow - [yellow][belly] - belly

strawberry

yellowbelly

Stimulus level

OT-componential

yellowbelly

belly

OT-noncomponential

jail

jailbird bird

Conceptual level

shoe [shoe][horn] horn

Lexical level

shoe - [shoe][horn] - horn

jail - [jail][bird] - bird

shoehorn

jailbird

Stimulus level

TO-componential

TO-noncomponential

Figure 2: Semantic transparency and componentiality in Libben (1998).

Many aspects of the model in Figure 2 appear to be on the right track. Yet, I would see the issue of semantic transparency in rather different terms today. First and foremost, it seems to me now that the model in Figure 2 suggests that morphological representations in the mental lexicon are still organized to get things right. In my 1998 model, rather than claiming as Sandra (1990) did, that transparent and opaque compounds

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undergo different computational procedures, I claimed that they undergo the same morphological processes. The difference between transparent and opaque compounds falls out from differences in their representations. This addresses the problem of requiring that the morphological parser know which type of compound is which. My view now is that there is likely much less difference between these structures than was first supposed. Semantic transparency effects have turned out to be quite elusive experimentally. As we showed in Libben et al. (2003), transparent and opaque compounds show comparable constituent priming patterns. A series of experiments by Pollatsek and colleagues (Pollatsek and Hyönä 2005), using the more ecologically valid eye-tracking paradigm, failed to find that semantically opaque words are disadvantaged in reading. More recently, Zwitserlood et al. (2005) reported that, in a picture interference task, German participants receive benefit from pictures associated with opaque elements of compounds, so that a picture of a hog facilitates the production of hogwash. The reason that I now think that the difference between transparent and opaque compounds is smaller than first expected is related to the title of this paper, “Everything is psycholinguistics”. It seems to me that it is safest to assume that morphological representations come from morphological processing. As I discuss in the concluding section, this has consequences for the distinction between independent and dependent variables in psycholinguistic research. But, restricting discussion to the domain of semantic transparency for the present, let me show why “everything is psycholinguistics”.

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2.3. An alternative view of semantic transparency

An easy and, I think, appropriate definition for psycholinguistics as a field is that it is the study of how we do language. I often begin undergraduate courses in psycholinguistics with the following simple demonstration. Students are instructed to do their best not to understand a word that they will hear. I count to three, and then say the word dog. Of course, unless you put your fingers in your ears, it is impossible not to understand the word. It seems to me that this is the fundamental truth of psycholinguistics. Everything happens automatically and obligatorily. Therefore, any psycholinguistic model that explains processing in terms of what does not occur for any particular class of stimuli, is likely to be on the wrong track. This would apply equally to the claim that opaque compounds are not decomposed, as well as to the claim that opaque compounds do not access conceptual representations for constituents (as in Libben et al. 2003). Rather, when differences in processing occur, I suggest that our best bet is to make appeal to more processing rather than less. My current view is that the effects of semantic opacity, when they do occur, are related to the extra processing that is required to deactivate spuriously activated constituents (Libben and de Almeida 2001; Libben, et al. 2004). At least some of the elusiveness of the semantic-transparency effect comes from the fact that psycholinguistic processing shapes the lexical system so as to diminish semantic-transparency effects. It is not unreasonable to assume that lexical processing creates large (and perhaps massively redundant) morphological representations in the mind so that, for example, there might exist a representation for straw as a free morpheme, and another representation for straw as the initial constituent of a compound

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(which we could represent as straw-). Although the compound strawberry would be semantically opaque if composed of the free morphemes straw+berry, it might be less so if composed of the bound morphemes straw-+-berry. This view of representational proliferation makes predictions that we are currently exploring in our laboratory. The first and most straightforward of these predictions is that morphological processing creates new representations, an idea that dates back in the psycholinguistic literature to Taft and Forster (1975). In recent work, Nault and Libben (2005) explored representational changes in German verb roots that might result from patterns of compound processing. In this work, bound German verb roots that occur in compounds (e.g., sprech in Sprechstunde) were compared to German verb roots that do not occur in compounds. In a lexical decision task, both these root types, when presented in isolation, should generate “no” responses, because they are not free-standing German words. This is exactly what happens. But verb roots that occur only in compounds take significantly longer to reject as non-words and show significantly more false positive errors (i.e., “yes” responses). It was reasoned that this pattern of results is due to the processes involved in compound production and comprehension, in which morphological decomposition gives these bound roots enhanced lexical status. If morphological processing creates new bound representations that could be homophonous with their free morpheme counterparts, then our calculations of semantic transparency of compounds should be substantially altered. Currently the semantic transparency or opacity of particular compounds is most reliably calibrated by administering a rating questionnaire to participants, in which they judge the extent to

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which the meaning of a word as a free morpheme corresponds to its meaning in the compound word. Clearly, this fails to capture the fact that some compound constituents must have their own representations as positional constituents as well as free morphemes. Consider the morpheme bat. As associated with a particular comic book and movie hero, this morpheme has acquired considerable frequency as an initial compound constituent. Batman drives a batmobile and a batboat, and rides a batcycle. He flies a batplane,

climbs a batrope, wears a batcape, and works in a batcave. All of these compounds are transparent if one posits that the bound compound modifier bat-, rather than the free morpheme bat, is the one that is employed in compound processing. A similar line of reasoning could be applied to compound heads with a substantial family size. Returning to the compound strawberry, we know that when subjected to a standard semantic-transparency rating task, its morphological head, berry, is given a rating of high transparency but its modifier, straw, is given a low transparency rating. However, when one takes the properties of the morphological family into consideration, it is possible that the compound is not processed as an opaque structure at all. The word strawberry belongs to a compound family in which opacity is much more the norm than

the exception. This family includes strawberry, raspberry, cranberry, rowanberry, loganberry, gooseberry, elderberry, boysenberry, mooseberry, and huckleberry, all of

which are opaque for most speakers. In my current thinking, the semantic nature of the berry family renders the modifiers of these compounds semantically inert, rather than

transparent or opaque. I suspect that the notion of semantic inertness might account for

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much of the ambiguity in the psycholinguistic literature on the role of semantic transparency in compound processing.

3. REFLECTIONS ON THE ENTERPRISE

The details of the relation between morphological families and semantic inertness discussed above still need to be worked out, but this promises to be an excellent domain in which to explore how language processing shapes the lexical system. At first blush, this doesn’t seem to be startling news. Words are acquired through exposure and use. The functional architecture of the mental lexicon surely develops to accommodate the patterns it must handle in normal online lexical processing. But if this is true, all the variables that we consider in psycholinguistic research are themselves part of the lexical processing system. Thus, there may be no identifiable language variables to be used in psycholinguistic research that are truly independent variables. Rather, we may simply be examining correlations between different aspects of lexical processing.

3.1. Are there any independent variables?

We psycholinguists use the terminology of the classic scientific method in our approach to language processing. It is the way we were taught. Hundreds of psycholinguistic articles have the form “The effect of X on Y”, which we interpret as the effect of some independent variable on some dependent variable. Yet, as we were also taught, the vast majority of variables that we use as though they were independent variables in a psycholinguistic experiment are not independent at all. For example, in the case of “The

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effect of age on Y”, where Y is some aspect of language processing, we know that the variable age is not a variable that can be assigned to one group or another. It is a characteristic of the organism, and one that is correlated of course with many other characteristics. As such, in a psycholinguistic experiment, age does not have an effect on processing. Rather, age is itself a property of that processing (as might be other participant characteristics such as gender, education, bilingualism, or aphasia). These comments, of course, apply to practically all participant characteristics. But I think it is also useful to consider how they apply to language variables that we might, for example, consider to be properties of words, rather than properties of people. Let us begin with lexical frequency, which is the stimulus variable that shows the most robust effect on lexical processing. Frequency is a value that we look up in an alphabetical listing in a book or a database. As such, it seems to be most appropriately considered to be a property of a word. Yet, on reflection, it is really a shorthand estimator of the state of a participant in an experiment. Perhaps it is a long-distance practice effect, comparable to the effects of participating in the same experiment two or three times. In such a case, we would be unlikely to conceptualize the experiment in terms of the effect of “practice” as something that stands outside the organism. Rather, the appropriate conceptualization would be in terms of different states of the organism at various times. I think that we would be hard-pressed to find any putative independent language variables in psycholinguistic experimentation that are not of this type. Returning to semantic transparency, it seems to me that considerable confusion results when we ask whether transparent words are processed in this way or that way. Rather, semantically

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transparent words can only be operationally defined in terms of how we process them. A word can be considered to be semantically transparent for an individual user if both whole-word activation and constituent activation occur, if both generate meaning changes in the organism, and if the results of the meaning changes that result from whole-word and constituent activation are mutually facilitatory. Seen from this perspective, semantic transparency does not have a psycholinguistic effect. It is a psycholinguistic effect. This line of reasoning might be extended throughout our research on lexical processing. We talk about words being presented to participants in experiments. We describe a stimulus set in terms of so many monomorphemic words, so many compounds, and so many non-word foils. But if words are indeed “what you do”, then they have no existence in non-psycholinguistic terms. A compound is a compound if two or more constituent root morphemes are processed within it. If they are not, then that word is monomorphemic (at least for the individual participating in the experiment). If there is no meaning effect within the organism, then there are no morphemes at all. The consequence of all this, I think, is that in our psycholinguistic experimentation we need to remain skeptical of simply taking constructs off the shelf. If everything in a psycholinguistic experiment is psycholinguistic, we might find that the most useful set of constructs, the ones that will have the closest approximation to the behaviour of language users, are those that are defined within the domain of language use, that is, within the overall functioning of the organism.

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3.2. Psycholinguistics as art and science

Suppose that the constructs that we use as independent variables in our experiments are not truly independent, and should instead be defined in psycholinguistic terms. I suspect that we will continue to conceive of the language system as something out there. This is because it provides researchers involved in the formal description of language, as well as psycholinguists and neurolinguists, with a common vocabulary and a foundation for interdisciplinarity. Nevertheless, there is evidence to suggest that a conception of all psycholinguistic variables as co-varying within a processing system has already had the effect of leading us away from classical experimental paradigms in which a single independent variable is manipulated factorially. Rather, the trend that I perceive is toward a much more extensive use of multiple (and nonlinear) regression techniques to understand how factors interact during the course of language processing. If this is indeed the trajectory of research in the field, it has consequences for our conceptualization of not only independent variables, but dependent variables as well. One of the top priorities in our laboratory is to develop a program of experimentation that relates multiple experimental paradigms. This will allow us to understand not only the interrelations among language variables, but also the interrelation among tasks. I am hoping that our studies will, in the near future, incorporate in each experiment multiple dependent measures, including event-related potentials, eye-tracking for reading, and hand-tracking for writing. I am currently developing a technique of analysis that will allow simultaneously generated dependent variables to be correlated using what I have

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termed a Braided Online Response Graph (BORG). However, as with the move from the exclusive study of monomorphemic words to multi-morphemic words discussed above, this approach has a methodological price associated with it. It is more expensive in terms of the cost of the equipment required. It is more time intensive both for participants in an experiment and for the post-experimental analysis. And it is more complex conceptually. In many ways this approach seems like the wrong way to go. For, as many of us were taught early on, in science, simple is beautiful. This statement remains true. But the drive to simplicity must also take into consideration that in many ways psycholinguistics is not only a science, but an art as well. As a science, it is concerned with the development of studies that are valid, replicable, and public. As an art, it has the duty to bring forward the complexity of its subject matter. It seems to me that art has value to us because it brings to our attention aspects of beauty and subtlety that are always in our world but are not available to us unless they are brought forward by the skills and perception of the artist. All language researchers are charged with a similar responsibility: to bring forward the subtlety, the complexity, and indeed the beauty of the human language processing system. In the field of psycholinguistics, an integral part of this responsibility is to understand the aesthetic of this system in and on its own terms.

Appendix: The rise of morphology in the psycholinguistic literature

The phenomena that I have outlined in the main body of the paper are clearly interrelated, and they each offer a vantage point from which we can better understand whether the

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construct morpheme plays an identifiable role in lexical processing, such that words are parsed into morphemes during processing. Questions of this sort are clearly of interest to researchers who approach lexical processing from a linguistic perspective. But they have also increasingly attracted the attention of researchers who find the processing of multimorphemic words to be a tractable domain in which to explore the general cognitive factors that underlie the human ability to process complex stimuli. The result of this has been that morphology has moved much more to the centre of debate in psycholinguistics over the past years and has become a domain in which interdisciplinary discourse is more the norm than the exception. In Figure 3, this trend is represented graphically. The bar chart was constructed from the number of hits at time of writing using the Beta Release of Google Scholar with three sets of nested search terms. The superset term “psycholinguistic(s)” generates all books, journal articles, and citations, in which the words psycholinguistic or psycholinguistics appear. Unsurprisingly, there has been considerable increase in this number over the past 25 years such that in the period 19801984, 974 hits are recorded and by 2000-2004 this number rises to 7,600. Perhaps most revealing and relevant to our present discussion, however, is the relative proportion of psycholinguistic hits in which the term morphology also appears. This rises from 4% of the total in 1980-1984 to 25% of the total in 2000-2004. Research that involves the term compound shows a comparably dramatic rate of increase. In 1980-1984, only six hits

were recorded, comprising 0.6% of the hits for psycholinguistic(s). By 2000-2004, this proportion had increased eight-fold to 4.9%.

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100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Psycholinguistic(s) & Morphology & compound Psycholinguistic(s) & morphology Psycholinguistic(s)

1980-1984 1985-1989 1990-1994 1995-1999 2000-2004 6

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44

171

362

41

106

226

814

1890

974

1180

1820

3940

7600

Figure 3: Number of hits (which include journal articles, books, and citations) on

Goggle Scholar Beta (2005) for three search sets. Bars represent five-year intervals over a period of 25 years. Colours represent percentages of the total, and the actual number of hits for each search set is provided in the table below the bars

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REFERENCES

Baayen, R. Harald., Richard Piepenbrock, and Hedderik van Rijn. 1993. The CELEX Lexical Database [CD-ROM]. Philadelphia, PA: Linguistic Data Consortium,

University of Pennsylvania. Libben, Gary.1993. A case of obligatory access to morphological constituents. The Nordic Journal of Linguistics 16:111-121.

Libben, Gary. 1994. How is morphological decomposition achieved? Language and Cognitive Processes 9:369-391.

Libben, Gary. 1998. Semantic transparency in the processing of compounds: Consequences for representation, processing, and impairment. Brain and Language 61:30-44.

Libben, Gary. 2006. Why study compounds: An overview of the issues. In The representation and processing of compound words, ed. Gary Libben and Gonia

Jarema, 1-21. Oxford: Oxford University Press. Libben, Gary, Lori Buchanan, and Annette Colangelo. 2004. Morphology, semantics, and the mental lexicon: The failure of deactivation hypothesis. Logos and Language 4:45–53. Libben, Gary, and Roberto G. de Almeida. 2001. Is there a morphological parser? In Morphology 2000, ed. Sabrina Bendjaballah, Wolfgang U. Dressler, Oskar E.

Pfeiffer, and Maria D. Voeikova, 213-225. Amsterdam: John Benjamins.

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Libben, Gary, Bruce L. Derwing, and Roberto G. de Almeida. 1999. Ambiguous novel compounds and models of morphological parsing. Brain and Language 68:378386. Libben, Gary, Martha Gibson, Yeo Bom Yoon, and Dominiek Sandra. 2003. Compound fracture: The role of semantic transparency and morphological headedness. Brain and Language 84:26-43.

Nault, Karin, and Gary Libben. 2005. Representation and processing of interfixed German verb-noun compounds. Paper read at the Canadian Linguistic Association annual meeting, London, Canada. Pinker, Steven. 1999. Words and rules. New York: Basic Books. Pinker, Steven, and Michael T. Ullman. 2002 . The past and future of the past tense. Trends in Cognitive Sciences 6:456-463.

Pollatsek, Alexander, and Jukka Hyönä. 2005. The role of semantic transparency in the processing of Finnish compound words. Language and Cognitive Processes 20:261-290. Sandra, Dominiek. 1990. On the representation and processing of compound words: Automatic access to constituent morphemes does not occur. Quarterly Journal of Experimental Psychology 42:529–567.

Taft, Marcus and Kenneth I. Forster. 1975. Lexical storage and retrieval of prefixed words. Journal of Verbal Learning and Verbal Behavior 14:638–647.

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Zwitserlood, Piene, Jens Boelte, and Petra Dohmes. 2005. Morphological relatedness blocks semantic competition-for-selection in speaking. Paper read at the Cambridge workshop on morphological processing, Cambridge, UK.

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