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.

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.

A software blogger takes on the heady task of defining categories. It's not clear to me if this is prescriptivist poppycock, naive descriptive lexicography, or wishful thinking: The Difference Between A Developer, A Programmer And A Computer Scientist. I made my own foray into this world here: Computational Linguistics vs. NLP.

HT zelandiya (via #linguistics)

Prototypical Podcast

(image from LearnOutLoud.coReading m)

Eleanor Rosch seems to have come out of semi-retirement and is teaching a new course at Berkeley on Buddhist psychology, complete with podcasts here.

Reading Rosch in graduate school was a transformative experience fort me. Her empirical work on cognition and prototype theory changed many of my ill-formed preconceived notions about how the mind works. She created clever and intelligent methods for studying how humans naturally categorize. Her findings were astonishing.

From The U. Pitt School of Information Science - Hall of Fame: "A basic tenet demonstrated by Rosch's experiments is that people classify an everyday object or experience less on abstract definitions than on what they regard as the best representation of the appropriate category. For example, a robin is considered a much better prototype for the concept of a bird than is a chicken or an ostrich. Her findings led Rosch to develop a hierarchy of basic, superordinate, and subordinate categories that "provide maximum information with the least congitive ability."

"Historical Vegetarian"

This summer I will be celebrating my 30th year as a vegetarian. Yippy for me. There are many ways to be a vegetarian and I'm often asked "what kind of vegetarian are you?". There are many ways of answering this question.

1) I could use one of the names that have emerged as labels for "dietary practices commonly associated with vegetarianism" (as this Wikipedia page explains ... it lists more than ten names).

2) I could list the things I eat, so I could say something like "I don't eat fish or meat. I'm not opposed to dairy, but it's a small part of my diet (mostly cheese). I'm not opposed to eggs, but I rarely eat them".

I rarely say either of the above. Instead, I typically say "I'm an historical vegetarian". I coined this term decades ago in order to sum up my answer, which has nothing to do with what I eat, but everything to do with when and why I became a vegetarian.

I chose to became a vegetarian in the late 1970s when I was seven years old for one reason and one reason only: My oldest brother Rob decided to become one. Rob was around 16 at the time, and if my understanding of the late 70s is accurate, every 16 year old was becoming a vegetarian. It was a fad. They all listened to disco, wore bell-bottoms (oh my, did Rob ever have the bell-bottoms!), and became vegetarians.

As a seven year old, I knew full well that Rob was the coolest person on the planet, so I followed him around and did whatever he did. He became a vegetarian, so I became a vegetarian and so did my brother Don. My mother didn't seem to mind (she probably rolled her eyes a few times, knowing the fad would pass, and decided to wait it out). I remember the first day remarkably well because my mother informed us that we were going to have hamburgers that night, and we all decided it would be wise to postpone our veggie inauguration by a day. But the next day, we stuck by our word and renounced meat (we allowed fish and fowl and dairy). My mother patiently cooked multiple dishes as was needed ... and waited.

Within a year, Rob was munching on hamburgers again. Within two years, Don fell off the wagon and dove into hotdogs with relish (frikkin sweeeeeeeet ambiguity! Both semantic AND syntactic. Parse THAT, LKB!).

And I was the last man standing. At ten years old, I renounced fish and fowl and dug in for the long haul. Somewhere along the line, my sister Lori became a vegetarian, but I think that was later. She held out for a good long while, but alas, she too has fallen off the wagon as well.

I've never quite understood my motivations for sticking it out, except perhaps the stubborness of a youngest child. But I have never been comfortable with any of the silly labels that people have concocted for cutting up the vegetarian space. I'm most happy with vegetarian. Nice and basic level. But I find other people are not happy when I call myself a vegetarian. They seem to feel I've misled them somehow when I re-tell the little story. So I coined historical vegetarian to label the tiny little space in veggie-land that I occupy. It may be the case that I alone am properly labeled by this term (god I love my syntax sometimes!).