barrier verbs as negative verbs

This is the fifth in a series of posts detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (list of previous posts here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

Barrier Verbs as Negative Verbs

It has been assumed since at least Klima 1964 (pdf) that some verbs are inherently negative. This means that they entail that some event did NOT occur. For example, the (a) sentence is from Laka (1990:105):

a. The witnesses denied [that anybody left the room before dinner].
b. Jean neglected [to turn off the lights].

For (a), it should be intuitively clear to a native speaker of English that it is part of the semantics of deny which entails that the proposition encoded by the embedded clause is false. Similarly the end state of the lights in (b) should be on, the opposite of off. The verb neglect entails that the event encoded by the embedded clause did not occur. This inherent negativity is a crucial feature in the semantics of barrier verbs.

Core barrier verbs are negative verbs that indicate an event did not happen (some non-barrier verbs can be coerced into a barrier verb interpretation, by being used within the barrier verb construction, but these verbs do not meet barrier verb entailments outside of the construction).

a. The roof prevented the car from [getting wet] → the car did NOT get wet.
b. The law exempted Tom from [paying taxes] → Tom did NOT pay taxes.

Laka draws some testable conclusions about negative verbs based on their interaction with negative polarity items (NPIs). In (a) the NPI anything fails to be licensed by the negative verb deny, while in (b) a negative complementizer is selected that in turn licenses anything in the embedded clause.

a. *The witness denied anything.
b. I deny that the witness denied anything.

The negation entailed by deny is not consistent with the NPI anything. There are two kinds of NPIs, licensed and free. There are three criteria to distinguish NPIs:

1) 'Just' Force
The adverb just forces a ‘free choice’ interpretation (where ‘free choice’ = “press any key”; your choice, but you must choose one) interpretation on licensed NPIs.The adverb just reverses negation:

I didn’t eat anything = I ate nothing
I didn’t eat just anything = I ate something

2) Verb Force
Negative verbs (N-verbs) force licensed NPI sentences to become ungrammatical. N-verbs play no role in licensing any, so they play no role in grammaticality.

3) Affective 'All'
N-verbs license affective ALL reading of “a single N”; Laka says that “a single N” has no ‘free choice reading available” (110).

CONCLUSION -- NPI’s are licensed only in clausal comps of N-verbs.

My interpretation of Laka is that any means either ALL or ONE. Negated N-verbs entail the ALL reading. So, acceptable examples of a negative verb candidate embedded under a negative verb in a clausal complement with an NPI should establish the legitimacy of that candidate verb as an N-verb (Phew! That's a sentence only a linguist could love).

In order to test the interaction between barrier verbs and NPIs, I performed a set of simple tests. First, I created a template of four sentences, each representing a verb’s interaction with the NPI anything. Then, I inserted each barrier verb into the verb slot and judged the grammaticality of the result. Then, I Googled searches of the form "* from [barrier verb] anything". This was designed to return cases of verbs that took a clausal barrier verb + NPI complement. Two examples here should suffice:

prevent

a. *Bob prevented anything.
b. *John prevented Bob from anything.
c. John didn’t prevent Bob from anything.
d. John prevented Bob from preventing anything.

Google results for "* from preventing anything"

• FEMA must be prevented from preventing anything when hours are lives.
• What is to stop the govt from preventing anything from being shown "for the good of society"?
• I stopped my firewall from preventing anything from working and i reinstalled limewire.

protect

a. *Bob protected anything.
b. *John protected Bob from anything.
c. John didn’t protect Bob from anything.
d. John prevented Bob from protecting anything.

Google results for "* from protecting anything"

• In addition, an "idea/expression dichotomy" in copyright law prevents copyrights from protecting anything on the "idea" level.
• Far from protecting anything, the technobabble creates a pointless risk.

What these tests show is that barrier verbs by and large do not allow an NPI unless they are first embedded under a negative verb, like the I deny that the witness denied anything example. This, at least at first blush, confirms that English barrier verbs are N-verbs under Laka’s definition. The second Google protect sentence (Far from protecting anything) is particularly interesting in that it seems to be the preposition from which licenses the NPI, suggesting that from has a negative entailment all its own, which conforms to Jackendoff's and Van Valin's analysis (yet to be discussed).

In the (a) examples below, the verb stop is neutral with respect to the event of barking; it is the presence of the word from which adds the negation in (b):

a. Chris stopped the dogs barking = the dogs were barking, then they stopped
b. Chris stopped the dogs from barking = the dogs were never barking

In the examples below, the verb prevent negatively entails the event of barking, regardless of the presence of the word from

a) Chris prevented the dogs barking = the dogs were never barking.
b) Chris prevented the dogs from barking = the dogs were never barking.

One of the issues here is the temporal relationship between the event of preventing and the event of barking. Barrier verbs entail no temporal overlap between the two events. This will be taken up in a later post.

barrier verb construction and selectional preferences

This is the third in a series of post detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (one here, two here).

The Barrier Verb Construction Template
I will use the term construction loosely to mean a syntactic template composed of slots which constrain their fillers syntactically or semantically. Barrier verbs fit into the following general constructional template:

NP1 verb-bar NP2 from/against NP3/VP

In this construction, the syntactic subject of a barrier verb (NP1) is either the agent which wields the barrier as an instrument, or the instrument itself. NP2 is the goal-directed participant and the complement NP3/VP represents the goal or outcome. For example, in both sentences below the government impedes the refugees from achieving their goal of entering the country.

• The government barred the refugees from the country.
• The government barred the refugees from entering the country.

Note that the event of entering the country can be represented by the NP the country and is presupposed to be intended, but not yet achieved (I assume some sort of coercion process allows for the event interpretation.). The PP complement in this construction involves either the preposition from or against (Not all barrier verbs allow the against alternation; this will be taken up in a later post) and represents the goal.

Many of the verbs I identify as barrier verbs occur in other lexical-semantic classifications like Levin (1993), FrameNet, Korhonen and Briscoe (2004), Brew, and Bresnen. For example, Korhonen and Briscoe list a FORBID class which includes prohibit and ban and a LIMIT class which includes restrict and restrain. Yet, no classification to date has recognized a single, natural class of barrier verbs which exhibit the properties this dissertation discusses. This is a reminder that no classification is perfect. FrameNet includes four frames which overlap somewhat with barrier verbs, namely HINDERING, PREVENTING, PROHIBITING, and THWARTING. However, none of these four frames recognize a superordinate category frame, something like BARRIER, which classifies the verbs presented in this dissertation as a single coherent class.

Therefore, I argue that barrier verbs constitute a natural, coherent class of verbs with the unique cluster of syntactic, semantic, and lexical properties found in Table 1 (forgive the fuzzy old fashioned MS Word image):

It is the lexical preferences for complement type that intrigues me more than any other fact about these verbs. For example, prevent almost always occurs with an ING complement but actually can occur with an NP. This is not strictly a selectional restriction because violations are possible, acceptable, and grammatical (and non-metaphorical), they are just low frequency. I'll post more about this later, but its juicy and weird and cool.

The following verbs are argued to be ‘core’ members of the class because they contain basic barrier verb semantics in their default lexical entries:

ban, bar, barricade, block, deflect, detain, discourage, enjoin, exclude, exempt, guard, hamper, hinder, interrupt, obstruct, occlude, protect, screen, shield, pre-empt, prevent, prohibit, restrain, restrict, thwart

As will be seen below, the construction is productive and many more verbs can take on barrier semantics. As attested by corpus evidence, the following 64 verbs can all occur in the construction with from and some allow against (not only is it OK if you find some these are not obviously barrier verbs at first glance, but in fact, that's the point! The construction coerces non-barrier verbs into the barrier verb semantics):

avert, ban, barricade, defend, deflect, derail, detain, exclude, exempt, guard, harbor, hide, insulate, occlude, protect, relegate, screen, secure, shackle, shield, avoid, bar, block, bond, check, constrain, curb, delay, deter, disable, discourage, embarrass, encumber, enjoin, foil, forestall, freeze, frustrate, halt, hamper, hamstring, handicap, hinder, hold, impair, impede, inhibit, interrupt, invalidate, keep, occlude, obstruct, obviate, outlaw, preclude, pre-empt, prevent, prohibit, proscribe, restrain, restrict, retard, staved-off, stay, stop, stymie, suppress, thwart.

More to come...

a verb class only a cognitive semanticist could love

Continuing my walk down dissertation memory lane (walk #1 here), this time I revisit the semantics of barrier verbs (and I remind you that this is largely a cut and paste job from my draft chapter on semantics).

Here is my set of "core" barrier verbs (I'll explain later how I distinguish between core members of a verb class and peripheral members as this was a topic of great interest to me).

ban, bar, barricade, block, deflect, detain, discourage, enjoin, exclude, exempt, guard, hamper, hinder, interrupt, obstruct, protect, pre-empt, prevent, prohibit, restrain, restrict, screen, shield, thwart

Note that neither stop nor keep are in the core set, yet either can easily be coerced into the barrier verb class. A keen spidey sense for semantics might also alert you to the fact that there are two sub-classes within that list: protect versus prevent. Oh, sooo much to discuss there. Too much for now, but yes, semantic madness lies that way.

My linguistics dissertation grew out of work by Len Talmy, so I’ll begin with a brief overview of his work on these verbs. Len wrote a 40 page monograph on this verb class and I may in fact possess the only extant copy. I really should scan that. I'll show in a later post how this semantic description impacts the syntactic construction that barrier verbs often occur in, as well as how the semantics impacts some quirky frequency facts. But for now, on with cognitive semantics!

The class of English barrier verbs are causative object control verbs* which encode the relationships between a goal directed participant (or “agonist” in Len's terms), its goal and a barrier participant (or “antagonist”). Situations involving barriers are more nuanced than simply one thing being in-between two other things. A barrier necessarily impedes the motion of one of the things it is in-between. Barrier situations require motion as well. However, we will see that this motion can be extended metaphorically to intentions and goals if not many other things. If an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb. Some examples:

Physical Blocking 

The fence blocked the car from entering the driveway. 

Intentional Exclusion 

The club excluded me from membership. 

Speech Act Pronouncement 

The judge banned journalists from the courtroom. 

Virtual

Spybot protected my computer from a virus.

In the examples above, there is an explicit goal directed agonist (the car, me, journalists, a virus) and a goal (the driveway, membership, the courtroom, my computer). Only in the first sentence is there a physical barrier (the fence). In the other sentences there is an implied barrier (the club’s power to exclude, the judge’s ban, Spybot). But in all cases, the barrier interferes with the goal-directed agonist's ability to achieve its intended outcome.

But interference alone is not enough to properly distinguish a barrier situation from a simple in-the path situation that a verb like place evokes in a sentence like this one:

John placed the table between Chris and the kitchen. 

In this case, to place does not necessarily evoke the notion of interfering with goal-directed motion. One would have to infer (perhaps via Gricean maxims) that Chris wants to enter the kitchen in order derive a barrier interpretation of this sentence. But that notion is not entailed by the verb place, it is at best added via inference. A member of the barrier verb class should entail the notion that the agonist is goal directed (via motion or metaphorical extensions of motion). Therefore, the two end points must have a particular relationship to each another. Namely, one end point participant must be moving towards the other, or have some sort of tendency towards the other end point (this use of tendency is adapted from Talmy).

Talmy assumes a model of barrier dynamics in which there are three salient participants: A GOAL-directed Agonist X, a barrier-forming Antagonist Y, and a GOAL Z. Figure 1 (Talmy loves figures) represents this state of affairs where the arrow represents the X participant’s tendency towards the Z participant.

Talmy also recognizes the potential for the inclusion of a SOURCE entity as well (“an object at which the Agonist begins its path” (unpublished manuscript: 2), but it is only these three salient X, Y, Z entities which form the necessary basic structure of barrier dynamics.

Note that the inclusion of a GOAL distinguishes this set of situations from simple impeded motion, lexicalized in such English verbs as “stop”:

• I stopped the lawnmower.
• The judge banned journalists.

In the first case, the lawnmower is not encoded with any inherent GOAL by virtue of the meaning of stop. This could simply mean that the lawnmower was turned off. Note, however that adding a complement with the preposition from adds the notion of GOAL:

• I stopped the lawnmower from destroying the flowers.

Above,  the verb ban encodes journalists with an inherent GOAL (presumably the judge’s courtroom as it would be pragmatically odd for a judge to ban journalists from her kitchen). Is this inherent tendency towards a goal a presupposition or invited inference or semantic entailment? Those arguments must wait for later.

What's crucial is that this tendency toward a GOAL is part of what constitutes the barrier situation and hence acts as a distinguishing feature which separates these verbs from other stopped-motion verbs like stop.

It is important to recognize that this set of situations is not just a possible set of events in the world but is actually lexicalized in certain English verbs, forming a natural class (there are cognate classes in Dutch and German and probably other languages). Identifying the properties of the verbs in this class (particularly with respect to the prepositions from and against) will require empirical, corpus based methods that will be the subject of later posts.

But what will really blow your mind is when I post about the difference betwen these two sentences:

Chris kept the dogs barking.

Chris kept the dogs from barking.

Chew on that for awhile.

*Maybe. I recognize that calling a verb a causative object control verb requires you to believe in such things as causative object control verbs, and some do not. There's really no escaping at least some theoretical stipulations.

I walk not alone through the valley of barriers

It's nice to not be alone. For years I thought I was the only one interested in barrier verbs. Happily, I have discovered several scholars who have published on this verb class recently. Here's a brief annotated, chronological, bibliography:

Landau, Idan. 2002. (Un)interpretable Neg in Comp. Linguistic Inquiry. Volume 33, Number 3, Summer. pp. 465-492. (This is a Minamalist Syntax treatment of Hebrew negation with just a short treatment of English prevent at the end). Infinitival complements to negative verbs (refrain, prevent) display a number of surprising syntax-semantics correlations. Those are traced to the operation of negative features in the Comp position. The analysis also provides insight into the recalcitrant prevent DP from V-ing construction in English.

Mair, Christian. 2002. Three changing patterns of verb complementation in Late Modern English: A real-time study based on matching text corpora. English Language and Linguistics, 6(1), 105-131. The article looks at three instances of grammatical variation in present-day standard English: the use of bare and to-infinitives with the verb help, the presence or absence of the preposition/complementizer from before -ing-complements depending on prevent, and the choice between -ing- and infinitival complements after the verbs begin and start. In all three instances, current British and American usage will be shown to differ, and these differences need to be interpreted against diachronic changes affecting Late Modern English grammar as a whole.

Baltin, Mark R. 2009. The Properties of Negative Non-finite Complements. NYU 
Working 
Papers
 In 
Linguistics,
 Vol.
2: 
Papers 
In
 Syntax,
 Spring. (Minamalist Syntax treatment of English from as it occurs with barrier verbs - this is a response to Landau). This paper is about the syntax and semantics of non-finite clausal complementation. By focusing on the properties of a small and comparatively neglected class of non-finite complements in English, this paper will shed light on the larger class of non-finite complements that have been the subject of much discussion, arguing that selection for complement type is semantic in nature rather than syntactic. 

Tomotsugu, Katsuko. 2013. Asymmetric causation types in the competing complements of negative causative verbs: NP (from) V-ing. The 12th International Cognitive Linguistics Conference (ICLC). University of Alberta in Edmonton, Alberta, Canada. 23-28 June. ("This study focuses on the omission of the preposition from from the complements of negative causative verbs, which represent the nonrealization of a situation expressed by V-ing.")

I would be remiss if I failed to remind y'all that several verb class scholars have recognized classes similar to barrier verbs, as I pointed out in previous posts, particularly here. The list of scholars who have touched on barrier verbs throughout history is actually longer, and goes back longer than this brief list suggest. These are simply four  recent examples that I have stumbled upon. Apologies to anyone who deserves to be listed here but is not, and if you know of such a person, please provide me with a citation and I'll gladly update the record.

On a side note, I asked both Baltin and Tomotsugu if they have also looked at the occurrence of against as an alternative to from with some of these verbs. Professor Tomotsugu and I have started a productive email exchange regarding the overlaps in our work. I have yet to hear from Professor Baltin.

The occurrence of against is particularly useful to establish the force dynamic properties underlying the semantics of barrier verbs because against is a preposition that means physical contact (e.g., ‘to lean against’). I didn't get a chance to discover what properties condition the occurrence of against instead of from, I suspect there is something interesting there. I think it has to do with the complement acting as a goal-directed agent, instead of the object of the barrier verb. Maybe it's that from makes the NP2 undergoer salient and against makes the NP3 antagonist salient? Not sure yet. But, note that the verb protect is used with both from and against in the following CDC passage in nearly identical contexts:

"The single best way to protect your children from the flu is to get them vaccinated each year. The seasonal flu vaccine protects against three influenza viruses that research indicates will be most common during the season: an influenza A (H1N1) virus, an influenza A (H3N2) virus and an influenza B virus."

The role of frequency has yet to be determined, but there is clearly a difference in the frequency of from and against in both American and British English, as Google Ngrams suggests (an imperfect corpus, I know, but a good hint):

Interesting linguistics, to be sure. More to come...

deep semantics 2: entailment vs. invited inference in barrier verbs

This is the sixth in a series of posts detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (list of previous posts here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

Deep Semantics 2: Entailment vs. Invited Inference

Even though barrier verbs appear to be clearly Negative verbs (see here), I will be careful not to overstate the logical relationship between the negative semantics of barrier verbs and the outcome of the complement event because in some cases the relationship seems like entailment, but in others it seems closer to invited inference. For example, in (a) it seems like the verb prevent entails that the car did not get wet; however, in (b), it seems plausible that, while Tom may be exempted from paying taxes, he went ahead and paid them anyway (perhaps by mistake).

(a) The garage prevented the car from getting wet.
(b) The IRS exempted Tom from paying taxes.

Simple presupposition involves the existence of some assertion in the background knowledge of all people involved which allows another assertion to be true. Here is a classic example from Chierchia and McConnell-Ginet 1990:

ASSERTION - Tom stopped smoking.
PRESUPPOSITION - Tom smoked.

In order to utter “Tom stopped smoking” felicitously, it must be assumed that the listener already knows that “Tom smoked”. In the example below, the barrier verb ban requires, on some level, the listener to believe that the journalists want to go to the courtroom:

ASSERTION - The judge banned journalists from her courtroom.
PRESUPPOSITION - The journalists want to go to the courtroom.

And, indeed, this belief passes the three primary tests for presuppositions:

NEGATION: The judge did not ban journalists from her courtroom.
QUESTIONING: Did the judge ban journalists from her courtroom?
CONDITIONAL: If the judge banned journalists from his courtroom, then their will be trouble.

The presupposition “the journalists want to enter the judge’s courtroom” survives under all three of these tests, but this alone does not mean that it is presupposed. There are presupposition-like phenomena which produce the same or nearly the same results. For example, if a person I don’t know very well came up to me and said, “my father just stopped smoking recently” I could infer (from Grice’s well known maxims of QUALITY and QUANTITY most likely) that her father had smoked previously and add that assertion to my background knowledge thereby making her utterance felicitous (and she could assume all along that that is exactly what I would do, also making her utterance felicitous). The assertion is not presupposed per se, but it is inferred and added to background knowledge in the moment.

One alternative is typically referred to as invited inference which mirrors many of the properties of presuppositions. Invited inferences are inferences we make based on background knowledge and our desire to follow basic principles of cooperative communication (ala Grice’s maxims). They can be very dependent on the verb they occur with. Saeed cites Levinson 1983 for the following examples:

ASSERTION - He cried before he finished his thesis.PRESUPPOSITION = He finished his thesis. 

ASSERTION - She died before she finished her thesis.
PRESUPPOSITION ≠ She finished her thesis.

Based on our knowledge of the world, we can recover or infer the fact that she did not finish in the second sentence. One possible analysis, that can save the presupposition, is defeasibility.

Defeasibility says, in essence, we do in fact make the same presupposition for the second sentence, but then we cancel it after checking with world knowledge. To test whether there is a consistent presupposition with all the barrier verbs, I performed the three presupposition tests above on a sub-set of all the barrier verbs in a preliminary NYT corpus. The goal was to perform the tests on two active sentences for each verb, preferably one with an NP complement and one with a VBG complement. This was not always possible, either because some verbs had no variation in complements in this corpus or there was a scarcity of active sentences (often these verbs are found in the passive or in nominals) or there was only one sentence found in the corpus for a particular verb (e.g., “to guard”). In the cases where there was no variation, two sentences with the same complement type were used. In the case where there was no good active sentence, one was formed from a passive with minimal adjustment (you will forgive this linguistic slight of hand as no change in the relevant meaning resulted. FYI, see Nunes* for a relevant discussion of the argument structure of deverbal nominal).

In the cases where only one sentence was available, the tests were performed on that one sentence and then the study proceeded on to the next verb. In all cases, a presupposition was contrived that could survive all the tests. Take, for example, the one sentence involving the verb guard:

Lavish and extensive measures guard the president from myriad threats.

If we take the “the president” to have a tendency away from “the myriad threats”, then how is that tendency to be paraphrased so as to test it with the presuppositions? As these tests are linguistic in nature, the linguistic form of the paraphrase of the situation feature of tendency is rather important to make sure the tests are being performed correctly. We might say that the assertion p is presupposed: p = The president wants to avoid threats.

NEGATION: Lavish and extensive measures do not guard the president from myriad threats.
QUESTIONING: Is it the case lavish and extensive measures guard the president from myriad threats?
IF/THEN: If lavish and extensive measures guard the president from myriad threats, then there’s going to be trouble.

One fine distinction can be made regarding speech-act barrier verbs like ban and exempt where it is possible that the undergoer of the prohibition is either not aware of it or chooses to flout it. This allows for the possibility that the prohibited event occurs despite the ban, making the negation of the event an invited inference rather than an entailment.

Thus, the jury is heavily leaning towards entailment for most core barrier verbs, but the jury is still out.


* Nunes, M. 1993. Argument Linking in English Derived Nominals. In Van Valin (ed) Advances in Role and Reference Grammar, John Benjamins, 375-432.

The Preposition 'from'

Having just now discovered I missed National Preposition Day, I offer a post relating to the preposition from and my dissertation.

It has long been noted that the English preposition from most typically occurs with Source (Huddleston and Pullum 2002; Van Valin and LaPolla 1997; Jolly 1991; Clark and Carpenter 1989a; Clark and Carpenter 1989b; Quirk 1985; Vestergaard 1977; Wood 1967).

(1) a. Chris returned from California.
b. Hide took the book from Atsuko.
c. Mike drove from Buffalo to Toronto.

There are some uses, however, where it appears to occur with Goals and Themes as well.

(2) a. The fence blocked the car from the driveway.
b. The tent shielded the kids from the rain.

When from occurs with verbs denoting barrier events like bar, ban, block, shield it can marks NPs representing either the unattained goal of the entity being blocked, or the restrained theme which failed to attain its goal. Interestingly, it can also mark VPs as in (3):

(3) The judge barred the journalists from entering the courtroom.

In my first qualifying paper (SUNY Buffalo’s linguistics department uses qualifying papers in lieu of a master’s thesis) I argued that from acts not as a preposition, but rather as a complementizer with barrier verbs.

The class of English “barrier verbs” (as originally sketched by Len Talmy) are negative causative object control verbs which encode the relationships between a goal directed participant (or “agonist”), its goal and a barrier participant (or “antagonist”). They are negative verbs in the sense of Laka 1994: they encode the negation of an event. Think of the verb neglect. If you neglect to do X, then X did not happen. With barrier verbs, if you ban X from doing Y, then Y did not happen.

These verbs fall into the following general constructional template:

NP₁ verb NP₂ from NP₃/VP.

In this construction, the subject of a barrier verb (NP₁) acts as the barrier (either directly or indirectly) to the achievement of a goal event (NP₃/VP) by a goal-directed participant NP₂).

I have recently discovered that Idan Landau has a detailed analysis of negative verbs in Hebrew which, extended to English prevent, suggests the complementizer interpretation as well. Though we have very different theoretical frameworks, I think we share some conclusions.

I’m interested in a variety of the phenomenon associated with barrier verbs (including the potential for a coercion analysis of the NP replacement of complement VPs)

. UPDATE: Barbara Partee discusses negative events in this Language Log post.

deep semantics 3: barrier verbs and aktionsart

This is the seventh in a series of posts detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (list of previous posts here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

Barrier Verbs and Aktionsart

Part of the semantic interpretation of barrier verbs involves event duration. Barrier verbs typically represent states (i.e., the temporal extent of the negated event is presupposed to have no necessary end boundary). Dowty described some basic tests for determining the Aktionsart class of a verb in a sentence. These now classic tests include the “occurs with X for an hour, spend an hour Xing” test for states and activities. However, some barrier verbs more readily allow a for an hour duration phrase than others.

For example, detain allows for an hour readily, but ban is less acceptable (to my American English speaking ears):

a. John was detained from entering Canada for an hour.
b. ?John was banned from entering Canada for an hour.

Although (b) is neither strictly ungrammatical nor strictly unacceptable, it intuitively seems like less of a default association between the stative event that the verb ban evokes and the duration phrase. I will stipulate, however, that (b) may be more acceptable to British speakers than American English speakers.

The verb detain seems to suggest a temporary state. However, none of these barrier verbs is strictly telic, as the in an hour test shows:

c. *John was detained from entering Canada in an hour.
d. *John was banned from entering Canada in an hour.

This is truly a fine grained semantic distinction requiring much more detailed analysis.

barrier verb subclasses

This is the fourth in a series of post detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (one here, two here, three here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

In order not to confuse Talmy’s description with mine, I will use different terms from this point forward. In defining the semantics of barrier verb, I will use the term “blocker” to refer to the participant who initiates or causes the blocking event to occur, the term “blockee” to refer to the participant which is affected by the blocking, the term “barrier” to refer to the participant which actually creates the blockade, and finally the term “outcome” to refer to the result of the event which was blocked (somewhat related to goals). These terms may have some overlap with well known semantic terms (e.g., “actor”, “agent”, “undergoer”, “patient” ,“instrument”, “resultative”); however, they are used here as labels of convenience, so they should not be confused with other terms used outside of this dissertation.

I will show that two semantically distinct subclasses of barrier verbs can be described:

Set 1) a prevent subclass where the syntactic object of the barrier verb is the blockee of the blocked event but presupposes an intention to achieve the outcome of the blocked event on the part of the blockee.

Example 1: Chris banned Wallis from going to the movies.

• Blocker = Chris
• Blockee = Wallis
• Barrier = speech act ‘ban’
• Outcome = seeing the movie

Set 2) a protect subclass where the syntactic object of the barrier verb is the blockee of the blocked event and presupposes a desire to circumvent the outcome.

Example 2: The doctor protects children from the flu with vaccines.

• Blocker = Doctors
• Blockee = the children
• Barrier = vaccines
• Outcome = getting the flu

The critical difference between the two classes is that prevent-type barrier verbs encode a negative relationship between the blocker and the blockee, while protect-type verbs encode a positive relationship between the blocker and the blockee. For example, in Example 1 above, it is presupposed that Wallis wants to achieve the outcome of seeing the movie and the blocker Chris stops Wallis from achieving this goal against Wallis's wish. In Example 2 above, it is presupposed that children want to avoid the outcome getting the flu and the blocker The doctor helps the children avoid this outcome.

The Verbs

Set 1 - prevent class

ban, bar, barricade, block, detain, discourage, enjoin, exclude, hamper, hinder, interrupt, obstruct, occlude, pre-empt, prevent, prohibit, restrain, restrict, thwart

Set 2 - protect class

deflect, exempt, guard, insulate, protect, screen, shield

On Ennui and Verb Classification Methodologies

Linguists and NLPers alike love word classes, especially verb classes. But linguistic categories are are tricky little buggers. They drove me to a deep ennui which led me out of academia and into industry.

Nonetheless, I occasionally retrace my old steps. Recently, I stumbled across an old chapter from my failed dissertation on verb classes and wondered if this little table of mine still holds water:

Here was the motivation (this is a cut and paste job from a draft chapter, largely unedited. Anyone already familiar with standard verb classification can easily skim away): The general goal of any verb classification scheme is to group verbs into sets based on similar properties, either semantic or syntactic. For linguists, the value of these classifications comes from trying to understand how the human language system naturally categorizes verbs within the mental lexicon (the value may be quite different for NLPers). One assumes that the human language system includes some categorical association between verbs within the mental lexicon and one attempts to construct a class of verbs that is consistent with those mental lexicon associations.

Verbs can be categorized into groups based on their semantic similarity. For example, the verbs hit, punch, kick, smack, slap could all be categorized as verbs of HITTING. They could also be grouped based on constructions. For example, verbs like give and send occur in both the ditransitive and double object constructions:
Ditransitive

Chris gave the box to Willy.
Chris sent the box to Willy.

Double Object

Chris gave Willy the box.
Chris sent Willy the box.

Verb classes have long been a central part of linguistics research. However, any set of naturally occurring objects can allow different sub-groups to be created using different criteria or features. The unfortunate truth is that we don’t really know how the mental lexicon is organized (this is not to say that patterns of relations have not been found using, say, priming experiments, or language acquisition, or fMRI. They have. But the big picture of mental lexicon organization remains fuzzy, if not opaque). Therefore, all verb classifications are speculative and all verb classification methodologies are experimental. Two key challenges face the verb classification enterprise:

1. Identify the natural characteristics of each class (e.g., defining the frame)
2. Identify the verbs which invoke the frame (e.g., which verbs are members of the class)

But how do we overcome these two challenges? There is, as yet, no standard method for doing either. Most verb classification projects to date have employed some combination of empirical corpus data collection, automatic induction (e.g., k-means clustering), psycholinguistic judgment tasks or old fashioned intuition. Nonetheless, in recent years there have emerged certain best practices which appear to be evolving into a de facto standard.

This emerging de facto standard includes a mixture of intuitive reasoning (about verbs, their meaning, and their relationships to each other) and corpus analysis (e.g., frequencies, collocations). Below is a table detailing methods of verb classification and some of the major researchers associated with the methods:

But how do we know if our speculations about a verb class are "correct" (in the sense that a proposed class should be consistent with a class assumed to exist in the mental lexicon)? The quick answer is that we don’t. Without a better understanding of the mental lexicon, we are left to defend our classes based on our methods only: proposed verb class A is good to the extent that it was constructed using sound methods (a somewhat circular predicament). We also have cross-validation testing methods available. If my class A contains most of the same verbs that your class B contains (using different methods of constructing the classes) this suggests that we have both identified a class that is consistent with a natural grouping. Finally, via consensus, a certain classification can emerge as the most respected, quasi-gold standard classification and further attempts to create classes can be measured by their consistency with that gold standard.

The closest thing to a gold standard for English verb classes is the Berkeley FrameNet project. FrameNet is perhaps the most comprehensive attempt to hand-create a verb classification scheme that is consistent with natural, cognitively salient verb classes. It is based on painstaking annotation of naturally occurring sentences containing target words.

But even FrameNet is ripe for criticism. It's not good at distinguishing exemplar members of a verb class from coerced members, save by arbitrary designation.

For example, I was working on a class of verbs evoking barrier events like prevent, ban, protect. What was curious in my research was how some verbs had a strong statistical correlation with the semantics of the class (like prevent and protect), yet there were others that clearly appeared in the proper semantic and syntactic environments evoking barriers, but were not, by default, verbs of barring. For example, stop. The verb stop by itself does not evoke the existence of a barrier. For example, "Chris stopped singing", or "It stopped raining." Neither of those two events involve a barrier to the singing or raining. Yet in "Chris stopped Willy from opening the door" there is now a clear barrier meaning evoked (yes yes, the from is crucial. I have a a whole chapter on that. What will really blow your mind is when you realize that from CANNOT be a preposition in this case...).

The process of coercing verbs into a new verb class with new meaning was a central part of my dissertation. Damned interesting stuff. I found some really weird examples too. For example I found a sentence like "Chris joked Willie into going to the movie with us", meaning Chris used the act of joking to convince Willie to do something he otherwise would not have done.

do we need parsed corpora?

Maybe not, according to Google: For many tasks, words and word combinations provide all the representational machinery we need to learn from text...invariably, simple models and a lot of data trump more elaborate models based on less data.

I've been wondering about this very issue for 5 years or so. When I first started collecting parsed BNC data for my defunct dissertation, I needed sentences involving various verbs and prepositions, but the examples I found were often of the wrong structural type because of preposition attachment ambiguity. I used Tgrep2 queries to find proper examples, but even then there were false positives, so I did some error correction. One of the more interesting discoveries I made was a relationship between a verb's role in its semantic class and its error rate.

I was trying to find a way to objectively define core members of a semantic verb class and peripheral members. I had a pretty good intuition about which were which, but I wanted to get beyond intuition (yes yes, it's all very Beth Levin).

For example, one of the objective clues for barrier verbs (a class of negative verbs encoding obstruction, like prevent, ban, exclude, etc) was the unusual role of the preposition from in sentences like these:

• She prevented them from entering the pub.
• He banned them from the pub.
• They were excluded from the pub.

The preposition from is usually used to mark sources (He drove here from Buffalo) but in these sentences it's acting much more like a complementizer. This is fairly unique to barrier verbs and I felt it was distinctive of the verb class, so I wanted a bunch of examples. Because I needed to exclude examples involving old-fashioned source from, I used a Tgrep2 search that required the PP to be in a particular relationship to the verb (the BNC parse was a bit odd as I recall, and required some gymnastics).

Again, I had a lot of false positives even with Tgrep2 so I did some manual error analysis and discovered that certain verbs had very low error rates while others had very high rates and the difference coincided nicely with my intuition about which verbs were core members of the class and which were peripheral: core members like prevent had very low error rates. This means that when prevent is followed by a from-PP, it's almost always the complementizer from; obvious to adults, the meaning of a barrier verb doesn't easily include source (necessary for old-fashioned from), but how would a kid learn that? If I ban you from the pub, how does a kid know the pub is NOT where you started (source) but rather the opposite, it's where you're not allowed to end up (goal)? Cool little learning problem, I thought ... and with a data set other than frikkin dative (which Pinker and Levin have, let's face it, done to death).

I assumed there was something central to the meaning of the verb class that caused this special use of from. Then it occurred to me, if this is true, why do I need the parse? Imagine I ignore structure, take all sentences where from follows a relevant verb, then sample for false positives. That should give me basically the same thing.

I became increasingly fascinated with this methodology. I was now interested in how I was studying language, not what I was studying. And that led me to ask whether or not the parse info was all that valuable for other linguistic studies? But then I realized that when big news stories start getting old, the media always, always starts reporting on themselves, on how the news gets made ... I didn't like where I was heading ...

...and then I got a job and that was that ...


HT: Melodye

British English and preposition dropping with barrier verbs

This is yet another in a series of posts detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (list of previous posts here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

preposition dropping and phrase length

Professor Katsuko Tomotsugu presented corpus data about preposition dropping and the NP (from) V‐ing construction, particularly with respect to British English and barrier verbs at this year's International Cognitive Linguistics Conference in Alberta. Here are three examples from her poster:

• The ozone layer still prevents any lethal UVC radiation reaching the earth. (FBL 3222)
• Closed doors stopped the fire taking over the whole building in Borough Road. (K4W 266)
• This somehow inhibits copies of viral DNA being made, and is the basis of acyclovir's anti‐viral activity. (B72 593)

I had noticed this preposition dropping and did a little leg work on it as well back in 2008 (all unpublished), so I thought I would add my two cents to Tomotsugu's data. Note, there is one glaringly obvious pattern to preposition dropping that I'll make plain at the end.

To begin, my focus was different. Tomotsugu was studying causation types and preposition dropping, but I wanted to know if heaviness (length of constituent phrase in number of words) was a factor in the occurrence of barrier verb sentences that dropped the preposition. I made the assumption this phenomenon was associated with British English, so I didn't associate my BNC extraction results with origin, but I think it's clearly a British English thing.

As I began looking in to this, it seemed like object pronouns had a high rate of co-occurrence with the prep drop sentences, so I counted that too (… to prevent them getting damaged). Note that there were no pronoun complements because I only looked at sentential complements. In order to find these kinds of constructions, I had to search a parse tree (using Tgrep2) for an S complement that was sister to an object NP (with no prep in between), so there are no passives in my data. Tomotsugu notes in her poster that passives are common:

A significantly higher frequency of complements using the passive form “being __” was found in the from-less variant of prevent and stop, as well as with verbs of occurrence (happen, arise, occur) in the from‐less variant of prevent.

I simply didn't study this. Note that automatically extracting examples of the prep drop condition with Tgrep2 was tricky, so I settled on one pattern that worked and stuck with it.  I may have missed others.

I found 211 examples of 'prevent X Ying', so I took 211 random samples from my 2152 original prevent from S returns as comparison. and counted the heaviness of the objects and from comps. The table below present the length of object and comp constituents occurring in the barrier verb construction with the construction prevent from S (note, there were zero valid prevent against S examples). Let me repeat my admission from the first post in this series that I am cutting and pasting much of this from chapters I wrote circa 2008. This data should be taken as suggestive only.

The number in the length column represents the number of tokens. The number in the Obj and Comp columns represent the number of sentences matching the length condition. For example, in the first row, it says that 104 ‘prevent X from Ying’ sentences had a verb object of only one token (this includes the 68 pronouns reported in orange above). Whereas, 178 'prevent X Ying' sentences had one word objects (of which, 160 were pronouns). On the other hand, only 4 ‘prevent X from Ying’ sentences had a verb object of 6 words, and only one ‘prevent X Ying’.

First pass interpretation:  The verb prevent is highly frequent, plus its association with the Barrier Verb Construction from is more frequent than other verbs.  This may account for its openness to preposition dropping (but the verb stop also allows prep dropping, even though its association with BVC from is weak).

More importantly, the prep drop sentences clearly had a bias for pronoun objects and they appear to have a bias for shorter comps too.  76% of the prep drop sentences had a pronoun object and 84% overall had a one word object. Of the 211 prep drop sentences, only 12 had objects of 3 words or more (5%); whereas, of the 211 sentences with a preposition, 42 did (20%).

In the from Y-ing sentences, complements on average are about 59% longer than direct objects (1.93/4.7 = .41); whereas in the preposition drop sentences, complements tend to be 67% longer (1.3/3.9 = .33).  Is this difference significant?  If it is, one could say preposition dropping is driven in part by length concerns.

Glaringly Obvious

And now for the glaringly obvious. Tomotsugu explicitly studied NP (from) V‐ing constructions. I did not. My Tgrep2 search extracted every S complement that was sister to an object NP (with no prep in between), regardless of POS. I believe I specified these POSs within my tgrep2 search:

VB|VBB|VBD|VBG|VBI|VBN|VBZ|VVB 

But, every example I retrieved, all 211 in the prevent X S query, involved a VBG complement. Maybe my search query was bad (I can't find the actual Tgrep2 query at the moment, just a description of it within a document).

Here is a representative example of my BNC returns:

1. Provided-that all the controls can be locked to prevent them getting damaged by slamming against the stops, parking the aircraft facing down wind will be safest, because then the wing is meeting the airflow at a negative angle.  
2. Although many gliders have a spring or bungee in the circuit to reduce the snatching loads at higher speeds on the approach, this is seldom powerful enough to prevent them sucking open if they are unlocked  
3. how can I prevent it happening again?  
4. It is free of charge and can help to detect early signs of health problems and prevent them developing. 
5. Even-if you decide you don't have a problem now, it makes sense to do all you can to prevent it happening in the future.  
6. Their main concern was that independent arbitration would drag out negotiations and prevent them complying with the MMC proposals to free pubs from the tie by the deadline of November 1992.  
7. That has not prevented them exercising a great influence on our cultural development. 
8. He got off the mark with an uppish straight drive for four, which might have given a less myopic bowler than Malcolm a return catch, and in Malcolm 's next over, he attempted a square slash which, if he had got an edge, might have prevented him ever setting foot in India again.  
9. “The reason that Hollywood keeps selling all its film companies to the Australians, the Japanese, and-so-on, is to prevent them falling into the hands of people from New York.”  
10. Her employers, the Northern regional health authority, want to prevent her returning there, to end her secondment as a neo-natologist in Newcastle-upon-Tyne, and for the foreseeable future prevent her working in child abuse.  
11. Even a nervous pull into the greenside bunker with his third shot at the par-five 18th, which was to open the door for Stewart and Olazabal, could not prevent it being Langer's day.  

This deserves more work, to be sure.

corpus data 1: barrier verb frequencies

This is the eigth in a series of posts detailing data and analysis from my not-quite-entirely-completely-achieved linguistics dissertation (list of previous posts here).

Recall that if an entity wants to achieve a certain outcome, yet is impeded by some force, this situation can be encoded by a barrier verb in English, such as prevent, ban, protect.

Corpus Data

All data was extracted from The British National Corpus in roughly 2007 (yeah yeah, I could re-do this ... someday). Below are four tables representing the co-occurrence percentages of the most frequent verbs in each of the four categories for which I extracted barrier verb data.

Recall that barrier verbs can occur in one of four full syntactic templates* (S = clause, or an ING verb) which I call the Barrier Verb Construction (BVC):

• A: verb X from S — prevent bad guys from stealing the TV.
• B: verb X from NP — exclude students from the auditorium.
• C: verb X against S — guard against getting athlete's foot.
• D: verb X against NP — defend yourself against the police.

Without getting into the greasy details, the BVC data below was extracted from a parsed version of the British National Corpus, so it involved more than mere word frequencies (it required specific syntactic relationships to hold in tree structures). The numbers are sorted by the percentage of total occurrences (this equals the total BVC occurrences divided by the total frequency of each verb as reported by Adam Kilgarriff).

How to read the table: the verb prevent had a total frequency of occurrence of 10286 according to the Kilgarriff data. I found 2152 correct occurrences of prevent intype A of the BVC. I interpret this to mean that about 21% of all instances of the verb prevent (and its morphological variants) within the BNC occur within type A of the Barrier Verb Construction (i.e., with a from ING complement). On the other hand, the word suppress occurred 1311 times overall, but only two of those times did it occur in the BVC (i.e., with a from ING complement).

There is much more to be said about these stats. I offer this as a tantalizing morsel. To be continued...

*These four basic construction types do not include passives or sentences where there is only an implied complement.

An analysis of 'exempt'

I've just started a new blog for a dissertation support group at SUNY Buffalo. This is a copy of a post I put over there. I'm analyzing constructions involving a class of verbs Len Talmy named 'barrier verbs' like ban, prevent, and protect. Here’s one interesting tidbit about a word that is some what barrier-like: by a large margin, the word exempt most often occurs as a predicate adjective in copula constructions (hence, it is POS tagged JJ) as in the BNC example below.

“In certain circumstances, the vehicle will also be exempt from Vehicle Excise Duty Road Tax.”

Code: A0J
Genre: W_misc
Subject: W_nat_science
Medium: m_pub

(TOP (S (PP (IN In) (NP (JJ certain) (NNS circumstances) (, ,))) (NP (DT the) (NN vehicle)) (VP (MD will) (ADVP (RB also)) (VP (VB be) (ADJP (JJ exempt) (PP (IN from) (NP (NN Vehicle) (NN Excise) (NN Duty) (NN Road) (NN Tax) (. .))))))))

First Pass Analysis: the word exempt is like open, it can either be a state or an accomplishment, but it is most highly salient as a state.

1. the door was open
2. the door was opened (by X)
   

3. the organization was exempt
4. the organization was exempted (by X)

The passive sentences have an accomplishment reading. But these are rare. I think the reason the overwhelming majority of occurrences of the word exempt in the BNC are predicate adjectives is because the outcome state is the salient aspect of the event of exempting. The actor of the exempting event is almost irrelevant (it's typically a law: not animate, not volitional, indirect causer).

Contrast this with a speech act barrier verb like to bar:

1. A judge barred Britney Spears from seeing her children.

In (1), the actor of the barring event is an animate, volitional, direct causer.

Google Linguistics

Erin made the following well-taken point in a comment to this earlier post:

This appeal to the authority of Google is troublesome in linguistics, since we often refer to Google results for evidence for hypotheses about usage. That is documents indexed by Google as a data source, rather than its search results as authoritative figure, of course, but this may not be obvious to the average Joe. :\

I have used Google repeatedly to find instances of constructions that I could not find using standard corpus linguistics methods with hand compiled corpora like the BNC. Typically I’m looking for any instance, just to prove people really do say the thing I’m claiming is possible. For example, I needed to find some examples of passivized complements embedded under 60 different barrier verbs following this pattern:

a. I banned John from being examined by the doctor.
b. I banned John from getting examined by the doctor.

Many of the verbs I wanted to search for are low frequency in the BNC (e.g., barricade, derail, hamper, etc) so the likelihood of finding examples of passivized complements using say a Tgrep2 search is low. So, I ventured into the scary land of Google Linguistics. I used the search query “verbed * from being” and “verbed * from getting” Within a short time, I had multiple examples for most of the verbs I was looking for. I can’t imagine performing this task more efficiently with any other tool. Google really worked well under those circumstances.

Let me note that I have not used Google hit counts or page counts to derive any statistics regarding frequency of occurrence, though. When I do this sort of thing, I’m careful to use my common sense to decide if a return is from a native speaker or not, and often what I do is skim a page to see if there are any obvious ESL errors. Also, I use my own intuition regarding the acceptability of a usage (by pure coincidence, Peter Ludlow from U. Toronto will be here in Buffalo this week giving a talk on the role of linguistic intuitions).

One of the more thorough discussions of the use of search engines in linguistics research is Adam Kilgarriff’s “Googleology is bad science”, a squib from Computational Linguistics (2007, v33, 1)

He writes that the web is attractive to linguists because it is “enormous, free, immediately available, and largely linguistic”. But, he points out four major flaws:

1. search engines do not lemmatise or part-of-speech tag
2. search syntax is limited
3. there are constraints on numbers of queries and numbers of hits per query
4. search hits are for pages, not for instances.

Kilgarriff offers this alternative: “work like the search engines, downloading and indexing substantial proportions of the web, but to do so transparently, giving reliable figures, and supporting language researchers’ queries”

The squib goes on to detail how we might go about doing that in a principled way. It’s well worth the read.