I.       Informal overview of  the "Sabu" sentence

A.  The girl that Sabu wanted to leave wore a blue suit.

This is a commonplace type of complex sentence; I would expect four year olds to understand and use sentences of this type in certain contexts.


 (Actually the attachment or embedding of the second clause into the NP subject of the main clause makes this a more difficult sentence for adults and kids because it separates or interrupts constituents the main clause.  However exactly the same issues we are interested in arise if the dependent clause is attached to the object NP.  Compare, for example, "The dog barked at the girl Sabu wanted to leave."  Children find these much easier.)


B.    Complex sentences

Complex sentences are sentences built of more than one clause.  In this example we have two clauses (below), the first is the main clause and the second is a dependent (relative) clause connected via the pronoun "that" to the main NP.

 Of course it is often difficulty to do things consciously – especially report about them – if we try to talk about automatic unconscious actions.  Recall our discussion of William James questions about talking – is it part of psychology? 


One point of this exercise is to bring your tacit knowledge of grammar into consciousness so as to appreciate the complexity and beauty of human language.


C.    Determining Grammatical relationships: who did what to whom?

Almost everyone sees one or another of the interpretations.  Everyone should see that the main clause is about "the girl"

1.    Main clause:  "The girl ..(modifier).. wore a blue suit."

Sometimes referred to as the independent clause, this follows the basic sentence pattern, S->NP+VP.

2.    Dependent clause: "that Sabu wanted to leave"

A dependent clause cannot, as my English teacher said, "stand alone."  It is part of a larger complex.  In this case it is a modifier of the head of the main NP, "the girl."

The ambiguity lies in determining the role of the relative pronoun (that) which is coreferent with "the girl."  Is "the girl" the subject of "leave"?  Is it the object of "leave"?  

3.    Sabu with these gaps indicated:  "The girl that Sabu wanted to () leave () wore a blue suit.

4.    1. The girl (that) (Sabu wanted (the girl) to leave()) wore a blue suit.

5.    2. The girl (that) (Sabu wanted (Sabu) to leave (the girl)) wore a blue suit.

D.   Conclusion

We can see now why this is ambiguous – has two different interpretations depending on who is doing the leaving, and who – if anyone – is being left.

1.    A.  Implications for forming relative clauses – informally in 3 steps

a)   1. Create dependent clause with NP that is co-referent with the NP in the main clause to be modified.

In the Sabu example it is either 1) Sabu wanted the girl to leave or 2) Sabu wanted (himself) to leave the girl.

b)   2. substitute an appropriate relative pronoun for the coreferent NP in the dependent clause. 

For example in 1 above, "Sabu wanted (who/that) to leave" or in 2 above "Sabu wanted (himself) to leave (who/leave)"

c)    3. move the relative pronoun all the way to the left and attach to head of the NP in the main clause.  Leave a gap/trace where the pronoun was.

This gives us for 1) The girl who/that Sabu (the girl trace) wanted to leave….

And for 2) The girl who/that Sabu (himself) wanted to leave (the girl trace)…

2.    Implications for the mental lexicon (MD) entry for "leave"

"Leave" is a more complex verb "despot" that I realized when I first made up the Sabu sentence.  At the very least the MD tells us there can be several role playing NPS – NP1, an agent, NP2 an object, NP3 an indirect object, and maybe NP4 a place or permanent object.  Here are some examples that need further consideration:

a) Sabu left.

b) Sabu left the girl. (abstractly left in breaking a relationship)

c) Sabu left the girl. (walked away from her)

d) Sabu left the girl his car.

e) Sabu left Chicago.  (is this different from c?)


In the above examples, Sabu is always NP1. In b and c, (the girl) is NP2, and in d) we see two NP objects – (the girl) as an indirect object NP3 and direct object NP2.  Perhaps e) would be an example of NP4?

3.    Effects of loss of case marking in the development of English

We all know that some languages specifically mark or inflect NPs, indicating their role.  Presumably this makes comprehension easier.  English has some residual of this in the pronouns, "who" and "whom", along with  prepositions as in the following examples.

a-1) The girl for whom Sabu wanted to leave the car () wore a blue suit.

a-2) the girl whom Sabu wanted to leave the car for () wore a blue suit.

In these two, the "whom" tells us "the girl" is a kind of object.  You could imagine a language where a specific pronoun or inflection was available for all of these distinct NP roles.  Many languages have 5 or 6 cases; I've heard others may have 15 or more – probably not very popular languages?


II.   Three Types of complex sentences

Complex sentences are products of recursion – one sentence is used as part of another.  Informally, just count the number of main verbs – if there's more than one, it is a complex sentence.

A.  Relative clauses

Our first example was a relative clause.  Relative clauses may be further specified as "subject relatives" or "object relatives" depending on which NP in the dependent clause is coreferent with the NP in the main clause.

B.  Complement clauses

These are clauses that complete their phrases.  For example "Sabu wants the girl to go.", the clause fragment "the girl to go" tells us what Sabu wants.  Schematically, ((Sabu wants(girl go)).


"The fact that Otto knew was surprising." 


This is ambiguous, depending on whether the dependent clause is a complement (completes the head "Fact"), or a relative clause with a gap (x Otto knew (the fact->that) after "knew." 

The relative clause informs us about the head but unlike the complement, the relative does not state or "name" the head – i. e. Tell us what the fact is.

Note the following version of the complement clause: 

"That Otto knew was surprising."

This is not ambiguous.

C.  Conjunctions – (everything else)

In a sense, all complex sentences are conjunctions – one sentence conjoined to another, of ten with one or another morpheme – that, who, and, or if.

In some, like "S1 and S2", there is no clear "dependent" clause.

III. Video stars

You should be able to informally discuss these examples from the videos.

A.   Aphasia test

1.    The bird that the cat watched () was hungry.

B.   Language acquisition

1.    What do you think ((cookie monster eats (?))

Note the parallels with relative clause formation.  Here a complement clause, completes the thought, i.e. expressing a thought (the cookie monster eats (what?)).  The wh- pronoun moves to the left, forming the question with the help of "Do."

2.    When did the boy say (?) he hurt (?) himself.

Here the wh-time pronoun questions on of the adverbial "slots" or arguments in the dictionary entry for verbs – the time of the activity.  It is ambiguous due to the presence of two verbs, either of which might questioned as to "when."

IV.          Functions of complex sentences

Much of the great communicative and conceptual power of human language involves complex sentences.  Young children as early as two years use them to express 'wants', 'actions,' 'events' and shortly after age three, their beliefs. 


See Ruffman et al (2002) for a discussion of complex sentences of desire and belief and their role in development of theory of mind. (ToM).


These complement clauses "name" the desire, belief, action, or event they refer to.


Here is a table from Limber (1973) showing the variety of verbs used by young children.  All of these may be used with complement clauses.

Table 1       Complement Verbs Used during Third Year


Age 1;11-2:5                        Age 2;5-3;0



































aAuxiliaries excluded, e.g, going to, 'posted to, have to, and some modals.

bSay and go are used to express direct speech and noises, e.g, Cows go "moo."


The fact that children use these various verbs in object-complement (G1) constructions almost immediately upon using them in any construction (G2) should not, upon reflection, be very surprising.  For many of them like guess, wish, think, and pretend there is scarcely any way to refer to their objects other than by using a nominal complement of some type.  Where simple NP objects do appear in adult speech, those NPs must be interpreted as elliptical, [1]   e.g., I guess a goat, I suggest a goose, I think a martini.  Even I want a martini might be argued to imply some implicit verb whose object is a martini, e.g., to drink or have.

Complex sentences are put into the overall perspective on language acquisition in this sketch:



Limber, J. (1973). The genesis of complex sentences. In T. Moore (Ed.), Cognitive Development and the Acquisition of Language (pp. 169-186). New York: Academic Press.

[1] I have discussed these and similar examples in Limber (1969; 1970a)