Tests for constituents are diagnostics used to identify sentence structure. There are numerous tests for constituents that are commonly used to identify the constituents of English sentences. 15 of the most commonly used tests are listed next: 1)
The order in which these 15 tests are listed here corresponds to the frequency of use, coordination being the most frequently used of the 15 tests and RNR being the least frequently used. A general word of caution is warranted when employing these tests, since they often deliver contradictory results. The tests are merely rough-and-ready tools that grammarians employ to reveal clues about syntactic structure. Some syntacticians even arrange the tests on a scale of reliability, with less-reliable tests treated as useful to confirm constituency though not sufficient on their own. Failing to pass a single test does not mean that the test string is not a constituent, and conversely, passing a single test does not necessarily mean the test string is a constituent. It is best to apply as many tests as possible to a given string in order to prove or to rule out its status as a constituent.
The 15 tests are introduced, discussed, and illustrated below mainly relying on the same one sentence:
By restricting the introduction and discussion of the tests for constituents below mainly to this one sentence, it becomes possible to compare the results of the tests. To aid the discussion and illustrations of the constituent structure of this sentence, the following two sentence diagrams are employed (D = determiner, N = noun, NP = noun phrase, Pa = particle, S = sentence, V = Verb, VP = verb phrase):
These diagrams show two potential analyses of the constituent structure of the sentence. A given node in a tree diagram is understood as marking a constituent, that is, a constituent is understood as corresponding to a given node and everything that that node exhaustively dominates. Hence the first tree, which shows the constituent structure according to
The square brackets mark the conjuncts of the coordinate structures. Based on these data, one might assume that drunks, could, put off, and customers are constituents in the test sentence because these strings can be coordinated with bums, would, drive away, and neighbors, respectively. Coordination also identifies multi-word strings as constituents:
These data suggest that the customers, put off the customers, and could put off the customers are constituents in the test sentence.
Examples such as (a-g) are not controversial insofar as many theories of sentence structure readily view the strings tested in sentences (a-g) as constituents. However, additional data are problematic, since they suggest that certain strings are also constituents even though most theories of syntax do not acknowledge them as such, e.g.
These data suggest that could put off, put off these, and Drunks could are constituents in the test sentence. Most theories of syntax reject the notion that these strings are constituents, though. Data such as (h-j) are sometimes addressed in terms of the
The problem for the coordination test represented by examples (h-j) is compounded when one looks beyond the test sentence, for one quickly finds that coordination suggests that a wide range of strings are constituents that most theories of syntax do not acknowledge as such, e.g.
The strings from home on Tuesday and from home on Tuesday on his bicycle are not viewed as constituents in most theories of syntax, and concerning sentence (m), it is very difficult there to even discern how one should delimit the conjuncts of the coordinate structure. The coordinate structures in (k-l) are sometimes characterized in terms of non-constituent conjuncts (NCC), and the instance of coordination in sentence (m) is sometimes discussed in terms of stripping and/or
Due to the difficulties suggested with examples (h-m), many grammarians view coordination skeptically regarding its value as a test for constituents. The discussion of the other tests for constituents below reveals that this skepticism is warranted, since coordination identifies many more strings as constituents than the other tests for constituents.
These examples suggest that Drunks, the customers, and put off the customers in the test sentence are constituents. An important aspect of the proform test is the fact that it fails to identify most subphrasal strings as constituents, e.g.
These examples suggest that the individual words could, put, off, and customers should not be viewed as constituents. This suggestion is of course controversial, since most theories of syntax assume that individual words are constituents by default. The conclusion one can reach based on such examples, however, is that proform substitution using a definite proform identifies phrasal constituents only; it fails to identify sub-phrasal strings as constituents.
These examples suggest that the customers and put off the customers are constituents in the test sentence. Topicalization is like many of the other tests in that it identifies phrasal constituents only. When the test sequence is a sub-phrasal string, topicalization fails:
These examples demonstrate that customers, could, put, off, and the fail the topicalization test. Since these strings are all sub-phrasal, one can conclude that topicalization is unable to identify sub-phrasal strings as constituents.
Do-so-substitution is a test that substitutes a form of do so (does so, did so, done so, doing so) into the test sentence for the target string. This test is widely used to probe the structure of strings containing verbs (because do is a verb). The test is limited in its applicability, though, precisely because it is only applicable to strings containing verbs:
The 'a' example suggests that put off the customers is a constituent in the test sentence, whereas the b example fails to suggest that could put off the customers is a constituent, for do so cannot include the meaning of the modal verb could. To illustrate more completely how the do so test is employed, another test sentence is now used, one that contains two post-verbal adjunct phrases:
These data suggest that met them, met them in the pub, and met them in the pub because we had time are constituents in the test sentence. Taken together, such examples seem to motivate a structure for the test sentence that has a left-branching verb phrase, because only a left-branching verb phrase can view each of the indicated strings as a constituent. There is a problem with this sort of reasoning, however, as the next example illustrates:
In this case, did so appears to stand in for the discontinuous word combination consisting of met them and because we had time. Such a discontinuous combination of words cannot be construed as a constituent. That such an interpretation of did so is indeed possible is seen in a fuller sentence such as You met them in the cafe because you had time, and we did so in the pub. In this case, the preferred reading of did so is that it indeed simultaneously stands in for both met them and because we had time.
The one-substitution test replaces the test string with the indefinite pronoun one or ones. If the result is acceptable, then the test string is deemed a constituent. Since one is a type of pronoun, one-substitution is only of value when probing the structure of noun phrases. In this regard, the test sentence from above is expanded in order to better illustrate the manner in which one-substitution is generally employed:
These examples suggest that customers, loyal customers, customers around here, loyal customers around here, and customers around here who we rely on are constituents in the test sentence. Some have pointed to a problem associated with the one-substitution in this area, however. This problem is that it is impossible to produce a single constituent structure of the noun phrase the loyal customers around here who we rely on that could simultaneous view all of the indicated strings as constituents. Another problem that has been pointed out concerning the one-substitution as a test for constituents is the fact that it at times suggests that non-string word combinations are constituents, e.g.
The word combination consisting of both loyal customers and who we rely on is discontinuous in the test sentence, a fact that should motivate one to generally question the value of one-substitution as a test for constituents.
The answer fragment test involves forming a question that contains a single wh-word (e.g. who, what, where, etc.). If the test string can then appear alone as the answer to such a question, then it is likely a constituent in the test sentence:
These examples suggest that Drunks, the customers, and put off the customers are constituents in the test sentence. The answer fragment test is like most of the other tests for constituents in that it does not identify sub-phrasal strings as constituents:
These answer fragments are all grammatically unacceptable, suggesting that could, put, off, and customers are not constituents. Note as well that the latter two questions themselves are ungrammatical. It is apparently often impossible to form the question in a way that could successfully elicit the indicated strings as answer fragments. The conclusion, then, is that the answer fragment test is like most of the other tests in that it fails to identify sub-phrasal strings as constituents.
These examples suggest that Drunks and the customers are constituents in the test sentence. Example c is of dubious acceptability, suggesting that put off the customers may not be constituent in the test string. Clefting is like most of the other tests for constituents in that it fails to identify most individual words as constituents:
The examples suggests that the each of the individual words could, put, off, the, and customers are not constituents, contrary to what most theories of syntax assume. In this respect, clefting is like many of the other tests for constituents in that it only succeeds at identifying certain phrasal strings as constituents.
The VP-ellipsis test checks to see which strings containing one or more predicative elements (usually verbs) can be elided from a sentence. Strings that can be elided are deemed constituents: The symbol ∅ is used in the following examples to mark the position of ellipsis:
These examples suggest that put off is not a constituent in the test sentence, but that immediately put off the customers, put off the customers when they arrive, and immediately put off the customers when they arrive are constituents. Concerning the string put off the customers in (b), marginal acceptability makes it difficult to draw a conclusion about put off the customers.
There are various difficulties associated with this test. The first of these is that it can identify too many constituents, such as in this case here where it is impossible to produce a single constituent structure that could simultaneously view each of the three acceptable examples (c-e) as having elided a constituent. Another problem is that the test can at times suggest that a discontinuous word combination is a constituent, e.g.:
In this case,it appears as though the elided material corresponds to the discontinuous word combination including help and in the office.
Pseudoclefting is similar to clefting in that it puts emphasis on a certain phrase in a sentence. There are two variants of the pseudocleft test. One variant inserts the test string X in a sentence starting with a free relative clause: What.....is/are X; the other variant inserts X at the start of the sentence followed by the it/are and then the free relative clause: X is/are what/who... Only the latter of these two variants is illustrated here.
These examples suggest that Drunks, the customers, and put off the customers are constituents in the test sentence. Pseudoclefting fails to identify most individual words as constituents:
The pseudoclefting test is hence like most of the other tests insofar as it identifies phrasal strings as constituents, but does not suggest that sub-phrasal strings are constituents.
The fact that sentence (b), the passive sentence, is acceptable, suggests that Drunks and the customers are constituents in sentence (a). The passivization test used in this manner is only capable of identifying subject and object words, phrases, and clauses as constituents. It does not help identify other phrasal or sub-phrasal strings as constituents. In this respect, the value of passivization as test for constituents is very limited.
Omission checks whether the target string can be omitted without influencing the grammaticality of the sentence. In most cases, local and temporal adverbials, attributive modifiers, and optional complements can be safely omitted and thus qualify as constituents.
This sentence suggests that the definite article the is a constituent in the test sentence. Regarding the test sentence, however, the omission test is very limited in its ability to identify constituents, since the strings that one wants to check do not appear optionally. Therefore, the test sentence is adapted to better illustrate the omission test:
The ability to omit obnoxious, immediately, and when they arrive suggests that these strings are constituents in the test sentence. Omission used in this manner is of limited applicability, since it is incapable of identifying any constituent that appears obligatorily. Hence there are many target strings that most accounts of sentence structure take to be constituents but that fail the omission test because these constituents appear obligatorily, such as subject phrases.
Intrusion probes sentence structure by having an adverb "intrude" into parts of the sentence. The idea is that the strings on either side of the adverb are constituents.
Example (a) suggests that Drunks and could put off the customers are constituents. Example (b) suggests that Drunks could and put off the customers are constituents. The combination of (a) and (b) suggest in addition that could is a constituent. Sentence (c) suggests that Drunks could put and off the customers are not constituents. Example (d) suggests that Drunks could put off and the customers are not constituents. And example (e) suggests that Drunks could put off the and customers are not constituents.
Those that employ the intrusion test usually use a modal adverb like definitely. This aspect of the test is problematic, though, since the results of the test can vary based upon the choice of adverb. For instance, manner adverbs distribute differently than modal adverbs and will hence suggest a distinct constituent structure from that suggested by modal adverbs.
Wh-fronting checks to see if the test string can be fronted as a wh-word. This test is similar to the answer fragment test insofar it employs just the first half of that test, disregarding the potential answer to the question.
These examples suggest that Drunks, the customers, and put off the customers are constituents in the test sentence. Wh-fronting is like a number of the other tests in that it fails to identify many subphrasal strings as constituents:
These examples demonstrate a lack of evidence for viewing the individual words would, put, off, the, and customers as constituents.
The general substitution test replaces the test string with some other word or phrase. It is similar to proform substitution, the only difference being that the replacement word or phrase is not a proform, e.g.
These examples suggest that the strings Drunks, the customers, and could are constituents in the test sentence. There is a major problem with this test, for it is easily possible to find a replacement word for strings that the other tests suggest are clearly not constituents, e.g.
These examples suggest that could put, Drunks could, and could put of the are constituents in the test sentence. This is contrary to what the other tests reveal and to what most theories of sentence structure assume. The value of general substitution as test for constituents is therefore suspect. It is like the coordination test in that it suggests that too many strings are constituents.
These examples suggest that could put off the customers, put off the customers, and the customers are constituents in the test sentence. There are two problems with the RNR diagnostic as a test for constituents. The first is that it is limited in its applicability, since it is only capable of identifying strings as constituents if they appear on the right side of the test sentence. The second is that it can suggest strings to be constituents that most of the other tests suggest are not constituents. To illustrate this point, a different example must be used:
These examples suggest that their bicycles (his bicycle) to us to use if need be, to us to use if need be, and to use if need be are constituents in the test sentence. Most theories of syntax do not view these strings as constituents, and more importantly, most of the other tests suggest that they are not constituents.