Mixing Memory

Polysemy Is Like Homonomy, Only Different

I promised some further posts on the topic of metaphor, and on the conventionalization of metaphor in particular, but in order to get to that, we need to get some things out of the way first. Let’s start with polysemy. If you don’t know what polysemy is, then you need to study up on your Greek roots. Kidding, of course. Polysemy refers to a single word having multiple related meanings or senses. “Bank” is a good example of a polysemous word, especially since using it will help later in the post. Bank can mean the banking company, like Fifth Third Bank (that name has always cracked me up), it can mean the building where you deposit and withdraw your money or apply for a loan, or it can mean the action of doing bank stuff (“I bank at Fifth Third Bank; you know, the bank on Elm Street”). An important question for psychologists and psycholinguists is, how do we represent the different senses of polysemous words? Are they all represented as a single lexical unit (i.e., as one entry in our mental lexicon), called a lemma by linguists, or are they represented as separate lemmas?

To see the difference between one or multiple lexical units, consider the case of homonyms. Homonyms, as I’m sure you’re all aware, are words that have two or more unrelated meanings. “Bank” is again a good example. There’s the financial institution meaning of bank, and then there’s the incline next to a creek or river. These meanings are unrelated, and the fact that they are referred to using the same phonemes in the same order is probably just a coincidence. It’s pretty clear that the two unrelated meanings of “bank” are represented as separate lemmas. So we can rephrase the question about the representation of polysemous senses like this: are they represented like words with a single sense, are they represented like homonyms, or are their representations some hybrid of the two?

Greg Murphy and his colleagues have been doing really interesting work on this question lately, and they’ve come to the conclusion that polysemous senses are represented separately, like homonymous meanings. Their first line of evidence comes from experiments showing that polysemous senses, like homonymous meanings, interfere with each other. In one experiment1 Klein and Murphy had people learn a set of polysemous words presented in phrases (e.g., “daily paper”). After a delay, they were presented with a bunch of phrases, one at a time, and asked to indicate whether the capitalized word (which would be the polysemous word) had been in the set they’d previously learned. The key manipulation was how the word was presented. There were three conditions: a same phrase condition, in which participants read the word in the same phrase that they had learned it (“daily PAPER”); a different phrase, same sense condition, in which a different modifier was used, but the same sense of the word was retained (e.g., “liberal PAPER,” in which “paper” still refers to a newspaper); and a different sense condition, in which a different but related (i.e., polysemous) meaning of the word was presented (e.g., “wrapping PAPER”). Clearly, using the same phrase should produce the best memory accuracy, so the key comparison is between the different phrase, same sense condition and the different sense condition. If polysemous senses are represented as one lexical unit, then there should be no different between these conditions, but if they are represented as different lexical units, then accuracy in the different sense condition should be lower. That’s what happens when you use homonyms in this paradigm.

The accuracy rates for the same phrase, different phrase/same sense, and different sense conditions were 76%, 64%, and 56%, respectively. Each of those differences was statistically significant. To provide further evidence, Klein and Murphy conducted a second experiment using a different paradigm. When you prime people with one meaning of a homonymous word, and then give them another unrelated meaning of the term in a phrase and ask them to say as quickly as they can whether the phrase makes sense, they’re slower to do so than if you give them the same meaning both in the prime and in the sense/nonsense task. So, if polysemous senses of a word are reprsented separately, like homonmyous meanings, you should see the same pattern. Klein and Murphy found this using phrases like those in the previous experiment: particpants were significantly slower to verify that phrases containing polysemous words made sense if different senses were used in the prime and sense/nonsense task, than if the same senses were used. From these two experiments, it appears that polysemous senses interfere with each other, just as homonymous meanings do.

The next question, then, is how the separate representations of polysemous senses are related to each other. Klein and Murphy, in a seconc paper2, starting with the assumption that words “pick out” categories, offer several possibilities. Polysemous senses could be related to each other taxonomically, as many noun categories are (e.g., ANIMAL, BIRD, FINCH). They could also be related to each other thematically, like, say, the concepts BED and PILLOW. Finally, they might be related in an ad hoc fashion, as the members of the categories “things to take on a plane” and “things to take out of a burning house.”

In order to explore these possibilities, Klein and Murphy first looked at how people would form categories with polysemous senses. Their first three experiments used a forced sorting task. Force sorting tasks present people with one item, and then with two or more items that are related to the first thing in different ways (or are completely unrelated), and ask participants to choose the item that goes best with the first item. In their experiments, participants were presented with a phrase (the “target phrase”) that used a polysemous word. They were then asked to choose between a phrase containing the same word in the same sense or in a different but related sense, or a phrase containing either a thematically or taxonomically related word. For example. particpiants might have been presented with the target phrase “wrapping PAPER.” They would then be given another phrase with the word “pape” in the same sens, like “shredded PAPER”, or a different sense such as “liberal PAPER,” along with either a phrase containing a taxonomically related concept such as “smooth CLOTH” (paper and cloth are both types of material) or a thematically related concept such as “sharp SCISSORS” (scissors cut paper… rocks smash scissors).

In the first two experiments, they found that 80% of the time, participants chose either the taxonomically related or thematically related phrase over the phrase containing a different polysemous sense of the word in the target phrase, but when one choice was the target word used in the same sense, participants chose this 70% of the time. Murphy and Klein take this as implying that people don’t treat polysemous senses as forming a category. In a third experiment, however, they found that participants chose the related sense over the taxonomically or thematically related category 15% of the time, but when the choice was a homonymous meaning of the word in the target phrase or a taxonomically or thematically related word, participants chose the homonymous meaning only 7% of the time. So it appears that while polysemous senses are not very related, they are more related than homonymous meanings. In two follow-up experiments, participants continued to choose the phrase containing the related sense of the target word about 15% of the time even when they were “hit over the head” with the connection between the polysemous senses of the words prior to completing the forced sorting task.

So far, it looks like polysemous senses are related to each other in much the same way that homonymous senses are. However, in their sixth experiment, (11th, if you count the two papers together), they finally found a difference. For both taxonomically and, to a lesser extent, thematically related categories, category membership is a basis for induction. For example, if we know that both robins and finches are members of the category BIRD, and we are told that robins have two spleens, we’re likely to believe that the probability that finches have two spleens is pretty high, whereas knowing that robins have two spleens (they don’t, really, I don’t think) wouldn’t have much influence on whether we believe salmon have two spleens (especially since we know that some members of the category ANIMAL, a category in which both robins and salmon are members, don’t have two spleens). Klein and Murphy’s sixth experiment was designed to test whether people are willing to make inductions from one sense of a polysemous word to another, much as they will make inductions from one member of a category to another. Here’s an example from their task:

Suppose that scientists find the biotin bacteria in wrapping PAPER.
Type in the probability (out of 100) that the biotin bacteria will also be in liberal PAPER.

In addition to polysemous words, they also tested homonymous meanings. They found that the probabilities participants listed for inductions between polysemous senses were 1.5 to 2 (around 40%) higher than those they listed for inductions between homonymous meanings (20-30%).

At this point, you might be wondering what this has to do with dead metaphors, or maybe you’ve put two and two together. A full discussion of that will have to wait for a subsequent post, but for now I will quickly note that if metaphorical senses of a word become conventional, i.e., if they create a new sense for a polysemous word, the new sense will be stored separately from the original sense, and the relationship between the new sense and the sense from which it was derived will be only slightly stronger than that between homonyms.


1Klein, D. E., & Murphy, G. L. (2001). The representation of polysemous words. Journal of Memory and Language, 45, 259-282.
2Klein, D. E., & Murphy, G. L. (2002). Paper has been my ruin: Conceptual relations of polysemous senses. Journal of Memory and Language, 47, 548-570.

Comments

  1. #1 Shane
    November 3, 2006

    The second set of studies don’t tell us very much about the representation of word meanings. They do tell us about the meta-cognitive processes and strategies subjects use in sorting categories given the particular task context. The extent to which this is reflective of the structure of underlying mental representations is questionable.

    The first set of studies (The representation of polysemous words) tells us more, but its limited by the particular kind of polysemous senses they investigated. Polysemy varies from very closely related meanings, to distantly related meanings. The polysemous senses they used were on the distantly related end of the spectrum – akin to homonyms. Therefore it isn’t surprising they behaved like homonyms.

    So although these studies are congruent to the point you are trying to make, I think you could have quite easily found different studies (and present them uncritically) that would support the opposite view.

  2. #2 CA
    November 3, 2006

    “phrases containing polysemous words made sense if different senses were used in the prime and sense/nonsense task, than if the same senses were used.”

    Polypolysemony

  3. #3 Chris
    November 3, 2006

    Shane, I was pretty brief in describing the reasons for doing the second set of studies, but I think they show more than you. The forced sorting task is commonly used in concept research in cognitive psychology, and it’s generally taken to show the strength of different types of relations between concepts. I think if nothing else, these studies show that polysemous words have, in Klein and Murphy’s terms, “little semantic oveerlap.”

    What, specifically, do you think they show? And can you recommend some studies showing that polysemous words are represented with one lemma?

  4. #4 Chris
    November 3, 2006

    CA, hah, yeah, I was hoping that wouldn’t be confusing. I tried to use “sense” to mean polysemous senses and “meaning” to use homonymous meanings consistently throughout the post, and when I got to the sense/nonsense tasks, I realized I was in trouble.

  5. #5 Chris
    November 3, 2006

    Shane, one more thing. For further evidence that polysemous words are represented with different lexical units, check out Murphy’s paper using MEG.

    Pylkk�nen, L., Llinas, R., & Murphy, G. L. (2006). The representation of polysemy: MEG evidence. Journal of Cognitive Neuroscience, 18, 97-109.

    I didn’t talk about this study in the post because I didn’t want to have to explain the methods, but it’s something to check out if you’re interested in the issues.

  6. #6 Shane
    November 4, 2006

    Some use the term polysemes for different senses of a polysemous word which might have helped the meaning/sense problem in your explanation.

    Well, for one thing, and I made this point in the previous comment, is you can’t make strong claims about polysemy in general from these studies, only claims about a particular (weak) form of polysemy, and by extension, you can’t make much of a claim about metaphor either.

    As for studies that show polysemous words are represented by a single lexical entry, how about Pylkkänen, Llinás, and Murphy! I was prompted to find this before reading your response to my comment, and I haven’t read it carefully yet, but here is a quote from the conclusion:

    This study investigated the basic question of how the brain represents the sound-meaning connections of natural language. Specifically, we addressed the question of polysemy, asking whether multiple related meanings of a single phonological/formal code are represented as one word or as many. Our results support representational identity in polysemy: Multiple related meanings with identical sound representations form part of a single lexical entry

    http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1351340>

    They claim that the different polysemes do connect to the same abstract lexical representation (lemma), in a way that differs from homonymy, but that the different polysemes are “distinctly listed within that representation”. My interpretation of this paper (and related work by Beretta, Fiorentino & Poeppel (in press)), is that polysemy is not like homonymy, contrary to the point you are trying to make.

  7. #7 Chris
    November 4, 2006

    Shane, you’re right, in the Pylkkanen et al. they do ultimately conclude that homonyms are represented as one lexical entry, but “distinctly represented” in that entry. This is really what I would infer from Experiment 6 of Klein and Murphy (2002). Still, I don’t know another way to interpret any of the data that Murphy and his colleagues have produced, except to say that there is “little semantic overlap” between polysemous senses (“polysemes,” thanks for that, I’m going to use it from now on). In Klein and Murphy’s model, the amount of semantic overlap does vary between different polysemes, depending on the relationship between two polysemes (if one is a direct extension of another, its overlap with that one will be greater than with others, say).

    The point I’m going to try to make about metaphor is that when metaphors are dead, they create new lexical entries and/or representations within those entries. I’ll get to that argument in another post, though.

  8. #8 Chris
    November 4, 2006

    Forgot to add that my near obsession with conceptual metaphor theory developed only after Lakoff’s political career was launched, because he, and his theory, became so popular among people who didn’t know better.

    Now, I’ve always been interested in the issues, and began conducting studies in the area in ’99, which is well before Lakoff’s political fame, but then I was more interested in the fact that a.) Lakoff and Johnson were so popular in the humanities and b.) they were making claims to the effect that conceptual metaphor theory is the best supported and most influential theory in cognitive science. Plus, I’ve always been a fan of embodiment, and I think cognitive linguists give embodiment a bad name.

  9. #9 Shane
    November 5, 2006

    I would like to continue further on this discussion but its probably best to wait to for your next posts on the topic so you can make your position clear. Before that though, I will suggest what could be a reasonable possibility:

    There is a spectrum of sense relatedness from homonymy and polysemy , where at the homonymy end (which would include some cases of polysemy) we have single lexical entries for different senses , and at the (closely related) polysemy end we have a single lexical entry for different senses. Metaphor lies somewhere in the middle. It could be that some cases of metaphor (e.g. dead metaphor) behave like homonymy, and some cases like polysemy. For certain domains, such as time and space (where there is independent evidence for some shared neural substrates for processing space and time), the linguistic evidence of metaphors does reflect underlying similarities in processing between different domains, but in other cases the metaphors are dead. I wouldn’t say conceptual metaphor theory is correct, but that it highlights that in some cases something interesting is going on.

  10. #10 Matt G
    November 7, 2006

    I must say, I find experiments like these to be missing the point. I don’t question the validity of the results – on the contrary, they are exactly what we should have expected.

    But why is the question “How are polysemic word senses lexicalized?” being asked in the first place? Surely no one was ever claiming that the word “paper” as used in “liberal paper” and “wrapping paper” is being enlisted to refer to some atomic, Platonic concept of PAPER in our head. Yet if it’s not, then how are we going to get any traction about what’s going on in our heads by worrying over an imaginary entity called “the lexicon”?

    The point is that it is concepts, and their intricate and subtle relationships, that is doing the heavy lifting in cognition. And concepts are invoked by strings of words in context; even the seemingly unproblematic, unitary word-concept linkages (like, well, “paper”-PAPER) prove to be illusory upon further inspection.

    Let’s not kid ourselves … linguists focus on the surface manifestations of these concepts – words, and the organization of words into a grammar – because they are the most obvious, and unambiguous, forms of data available (unambiguous in their capacity as scientific data to be analyzed), NOT because they have been determined a priori to be the crux of the matter. In reality, these surface forms are merely the tip of a very profound iceberg. Consider the following two sentences:

    Suppose that scientists find samples of the biotin bacteria in wrapping paper.

    Suppose that you found a claim that scientists had found samples of biotin bacteria in the liberal paper.

    Is it of any use to us to focus on the artifact of the word “paper” in explaining how these statements are processed or understood? Surely as we hear or read the word “paper” at the end of each sentence we do not experience it in isolation, look it up in some sort of mental lexicon, and then try to disambiguate its meaning in this particular sentence. The very act of processing language in real time involves constant, unconscious predictions about what will (or could) come next, both at the level of grammar that sentence-diagramming types favor, and at the (to me, much more significant) conceptual level, based on the ad hoc constellation in concepts that has been activated prior to reaching the word.

    So of course polysemic senses “interfere” with each other: a given use of a particular word occurs in a particular context and the very activation of this context (in combination and competition with other relevant activations, like the auditory activation caused by the phonetics of “paper”) creates the effects described.

    As a final note, any theory of language processing and understanding has to naturally accommodate examples like:

    I did it for the pun of it.

    Of course this is an “atypical” linguistic datum, but it is far from anomalous. It merely casts the real forces at work here into stronger relief.

    It violates our expectations, while directing us (phonetically) to a particular conceptual interpretation that we had unconsciously entertained, while causing us to recognize that, yes, literally, you did do it for the pun of it, the whole enterprise of which (as it turns out) was quite fun (if not exactly HA-HA funny).

    I hope the experience of reading this post was at least a little fun.

  11. #11 Sandeep Gautam
    November 8, 2006

    To me the last study seems problematic. The sentences they used employed the same sense of paper.

    Suppose that scientists find the biotin bacteria in wrapping PAPER. Type in the probability (out of 100) that the biotin bacteria will also be in liberal PAPER.

    In both of the above sentences, reference to paper is in the sense of a material and NOT as a newspaper. The example that MAtt G quotes: Suppose that you found a claim that scientists had found samples of biotin bacteria in the liberal paper. leads to an activation of the newspaper sense, though even this sentence could have been phrased differently to remove ambiguity as to whether we are referring to a material or a newspaper.

    If this sentence as quoted by Matt was used in the study, then the results may make one rethink on ploysemy as represented by different lexical entities; else if the sentence as originally quoted by you was used, it reflects very poorly on the methodological aspects of the study.

  12. #12 Chris
    November 8, 2006

    Well, the ambiguity is part of the point. The question is to what extent do the representations overlap, and to show that, you have to use properties that apply to one aspect of one sense (polyseme), and see if people are willing to apply it to another sense. If they do, then you can infer that the aspect of the first sense is represented in the second, even if less strongly.

  13. #13 elham rahmani
    December 31, 2010

    I’m form Iran. /i nedd some article about polysemy words. this was very intresting and I approciate you. would it possible for you to send some article about polysemy wotrds? thanks

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