3.4 Learning Causativization
3.4.2 Overgeneralizing The Causative Alternation
In this section, the prediction of whether children have sufficient evidence to overgen-
eralize the causative alternation rule is tested using corpus data. As stated in Chapter 1,
I adopt the Sufficiency Principle (Yang 2016) here to determine when there is sufficient
positive evidence in the input. The Sufficiency Principle states that in order for a rule
to be generalizable, the number of exceptions to a rule for a class of N members must
not exceedN/ln(N). Following the Sufficiency Principle, the causative errors only arise
when the number of exceptions in the input are below the threshold to generalize this
rule to other members of a given class. This hypothesis can be tested by investigating
the causative errors made by children in corpus data (CHILDES, MacWhinney 2000). I
examined the child production data of Adam (Brown 1973) and Ross (MacWhinney 2000)
as two case studies of children who go through a stage of overgeneralizing the causative
alternation. These two children are good candidates to test the claims made in this chap-
ter as there is more data available for them than for most individual children in CHILDES,
and both of these children make causative errors.
3.4.2.1. Test Case 1: Adam
First, I look at Adam’s production data as a proxy for his vocabulary size. I examine each
is at age 3;2. Then, I investigated whether there was evidence for a causative form in
the input for the verbs produced by Adam. Each verb produced by Adam was checked
in the combined North-American CHILDES input data to estimate the input he has likely
received. Using this method, I determine whether the causative rule is productive for
Adam given his vocabulary size.
Adam produces several causative errors starting at age 3;2. The errors noted for Adam
often involve unaccusative verbs such as fall andgo, among others. Some of the errors
produced by Adam are shown in (43) below.
(43) a. don’t fall my head (3;2)
b. gon(na) fall him to pieces (3;7)
c. how to go it? (4;7)
d. if you can go it fast the pictures might run (4;7)
The causative errors for Adam extend until age 4;7; however, since the data for Adam ends
at age 5;2, we cannot say for sure when these errors stopped occurring. The errors we do
find indicate that the stage of overgeneralization lasts for as long as Adam’s corpus.
To establish whether the causative errors arose in the child production data from suffi-
cient positive evidence in the input, I examined Adam’s production data for each verb used
until the first unambiguous error was produced at age 3;2. Up to age 3;2, Adam produces
a total of 208 verbs in CHILDES.4 Out of these 208 verbs, 110 of them occur as intran-
sitive. From these verbs, I used intentionality as a guideline to distinguish between the
intransitive verbs produced by Adam. As seen early on in this chapter, intentionality not
only serves as a baseline for the divide between unergative and unaccusative verbs, but
it is also a cue that children recognize from infancy. Since intentionality is a cognitively
salient conceptual cue, it can be used here in analyzing whether the learner deems the
causative rule productive given their vocabulary and the verb classes the causative rule
4
potentially applies to. As shown later on, it is indeed primarily the class of unaccusative
verbs, or unintentional intransitive verbs, that undergo the causative alternation rule.
For Adam’s verbs, intentionality served as a rough divide for differentiating most
unergative verbs from unaccusative verbs. After identifying verbs showing intention-
ality, 51 verbs that lacked intentionality in an intransitive frame remained. These verbs
included two verbs, laugh and cry, which are generally classified as unergatives in the
adult grammar (Perlmutter and Postal 1984).5 The remaining 59 intransitive verbs were
intentional intransitives. Adam’s verbs and whether the causative alternation rule is pro-
ductive for Adam within a verb class is summarized in Table 3.3.
Table 3.3:Total number of Adam’s verbs sub-divided according to the way in which the verbs were used in child-directed speech. The causative alternation rule is productive for Adam for the class of unintentional intransitives, but not for the class of intentional in- transitives. The threshold of generalization was calculated using the Sufficiency Principle.
Verb Type # of Verbs Causative Verbs Threshold Productive?
transitive 98
intentional intrans. 59 9 44 no
unintentional intrans. 50 38 37 yes
Total 207 49
The table presented above summarizes the findings from the corpus search. The causative
alternation rule is productive for Adam for the class of unintentional intransitives, but not
for the class of intentional intransitives. Below, I further discuss the details of how the
rule comes to be productive for Adam.
Recall that Adam’s verbs were counted up to the first causative error by hand. The
verbs were then divided according to whether they were used as intransitives or only
transitives in the CHILDES input data. For this step, data from each caregiver in the
5
These verbs can eventually be learned as unergatives, under some readings,laugh, for instance, is
clearly intentional (e.g.,Susan laughed at his foolishness). For now, these verbs are grouped together with the class of unintentional intransitives, as the learner might not categorize these verbs that way immediately.
North American English CHILDES corpora were examined, rather than just the child’s
caregivers’ speech. The child’s production data within a single corpus can be used to de-
termine whether the child knows a verb, but because words in the input follow a Zipfian
distribution, they may not occur in every possible syntactic frame. The Zipfian distribu-
tion results in many verbs only occurring only a few times, or even just once in the input
data. To ensure that the corpus size was large enough for the verbs to occur enough times,
Adam’s verb’s argument structures were compared with the combined CHILDES input
data. The result was 109 verbs that occurred as intransitives and 98 verbs that occurred
as transitives. The intransitive verbs were then divided along the lines of intentionality.
The way in which the verb classes were obtained is summarized in Figure 3.5. For each
intransitive verb, I checked to see whether the verb occurred as a transitive causative in
the input. As shown in Table 3.3, 38 out of the 50 unintentional intransitives occurred in
a transitive causative frame, and only 9 out of 59 of the intentional intransitives occurred
in a transitive causative frame.
verbs
transitive intransitive
unintentional intentional
Figure 3.5:Classification of verbs using structural and conceptual cues.
Out of the unintransitive 50 verbs, 12 of them did not occur in a causative frame in
the input data in CHILDES. Many of these verbs likefalldo not have a causative form in
the adult grammar. Following the Sufficiency Principle, a class with 50 members requires
at least 37 verbs to show a property in order for the property to be generalizable. Here,
members of the class, and Adam makes causative errors.
In total, Adam used 59 verbs that were classified as intentional intransitives. Out of
these verbs, only 9 of them causativize in the input. Therefore, Adam does not overgen-
eralize the causative rule to intentional intransitives, as the Sufficiency Principle requires
44 verbs to follow the rule in order for it to be used productively. This result is consis-
tent with what we find in Adam’s production data. Adam makes no causative errors with
unergative verbs. Moreover, as only a fraction of the intentional intransitive verbs have
a causative form, it would be unexpected that the child would generalize the causative
alternation rule if they were taking into account the entire set of intransitive verbs. Col-
lapsing the two classes of intransitives into one results in only 47 out of 108 verbs that
causativize. The number of causatives then falls below the threshold of the Sufficiency
Principle. However, the total number of causative verbs falls also well below 50%. Given
this data, most models would not make predictions for the learner to generalize when
only a minority subset of a class follows a certain pattern.
3.4.2.2. Test Case 2: Ross
Another case study of the causative overgeneralization was obtained from Ross’s data in
the MacWhinney corpus. Like Adam, Ross also produced causative errors around the ages
of 3-4 years. Some of these causative errors are illustrated in (44).
(44) a. and my mommy might break this and fall this (3;0)
b. I want to disappear it (3;3)
c. and are you going to stay me at my new school at Pittsburgh (3;5)
d. to go it down my tummy (3;11)
e. how did it disappear this air out of here (4;2)
The last error found for Ross is around age 4;2. The errors here are clustered around the
unaccusative verbs.
To test whether there was sufficient evidence in the input in order for Ross to gen-
eralize the causative rule, I examined the verbs in Ross’s production data, and compared
them with the CHILDES input data. I counted each verb that Ross produced by hand up
to the point when he makes his first error, which was at age 3;0. For Ross, I obtained a
total of 121 verbs that were produced up to that point.6
Ross’s verbs were also categorized based on transitivity. Out of 121, 66 verbs occur
as plain intransitives in CHILDES. 42 of these intransitives showed intentionality. The
remaining 24 verbs were intransitives lacking intentionality, which also includedcry, an
unergative verb. 55 of the 121 verbs were transitives. The different verb types are sum-
marized in Table 3.4.
Table 3.4: Total number of Ross’s verbs sub-divided according to the way in which the verbs were used in child-directed speech. The causative alternation rule is productive for Ross for the class of unintentional intransitives, but not for the class of intentional intran- sitives. The threshold of generalizability was calculated using the Sufficiency Principle.
Verb Type # of Verbs Causative Verbs Threshold Productive?
transitive 55
intentional intrans. 42 7 31 no
unintentional intrans. 24 18 16 yes
Total 121 25
As seen in Table 3.4, 18 of the 24 unintentional intransitive verbs occurred with a causative
form in the input in CHILDES. A class with 24 verbs requires 16 for the rule to be gen-
eralizable, 18 verbs is above that threshold. Thus, we find that there is sufficient positive
evidence for the causative alternation rule in the child-directed input for the verbs that
Ross has learned up to this point. This sufficient evidence leads him to overgeneralize the
causative rule to other verbs in the class. Consequently, Ross makes causative errors.
6
Additionally, we also see that there is insufficient evidence for the rule to be productive
for the subclass of intentional intransitives. Only 7 out of the 42 verbs in this category oc-
cur as causatives in the child-directed input. Moreover, the two intransitive types cannot
be collapsed into one. If the two intransitives types were treated as one group, for a total of
66 intransitive verbs, only 25 would have been witnessed in the transitive causative frame.
Once again, this number falls below the threshold of the Sufficiency Principle. With less
than 50% of the intransitive verbs undergoing the alternation, however, it would also be
unexpected under most learning models for the learner to generalize the rule when it is
not followed by the majority of the members of that class.