Utterance Length in Children Verses

Utterance Length in Children Verses Chimpanzees

Language is the essential foundation of the human species. Yet, is it completely unique to mankind? Several studies have shown that out closest relatives have a relatively strong grasp on the techniques and methodologies of language; however, chimpanzees have proven to be unable to pass the language capacity of a small child as measured through analysis of the Mean Length Utterance. However, much more study needs to be done in the convening of verbal and nonverbal associations of language and all of its complexities.

The Mean Length of Utterance, or the MLU (Dwyer, 1986), refers to the actual length of the sentence uttered in terms of words and morphemes within a particular sentence. These include blends of both free and bound morphemes, which can either stand alone as a single word, or must be attached to other forms of speech to create a discernable word within a sentence. An actual utterance is a complete unit of speech which does not depend on other grammatical forms to survive as an independent word.

The Mean Length of Utterance is found through observing 100 utterances of a child or chimpanzee. One this number has been successfully collected, the number of morphemes within that child or chimpanzee's speech is divided by that number of utterances, 100, (Bishop & Adams, 1990). As the number related to the MLU increases, so does the language proficiency of that particular individual. According to the study conducted by Bishop and Adams in 1990, the reading level of a typical eight-year-old is represented by a 4.5 MLU. This sets a high standard for chimpanzees to follow to reach such high levels of language proficiency.

A study conducted in 1990 by D.V.M. Bishop and C. Adams was aimed at finding the average MLU of normal children with average verbal communications. The study took children of various ages, topping out at around nine to ten years of age, were studied for their average MLU, in regards to the complexity of their sentence, (Bishop & Adams, 1990). At the normal third grade level, with a child of an average of eight years old, holds an MLU of around 4.5 based on their normal sentence structures. This presents a very good average MLU for the idea of the normal child in his or her level of language development. With this as a concrete basis, one can branch out into non-normal human children as well as our closets biological relatives, the chimpanzees.

The previous studies covering this topic represent a unique idea of the differences and similarities between the utterance of young children and chimpanzees. One of the most relevant studies juxtaposing the MLU of children to those of chimpanzees was conducted by David Dwyer of Michigan State University in 1986. This particular study focuses on the comparison of both children and chimpanzee's Mean Utterance Length, but in a very different context than what most people would assume to be a study based on researching the origins of language. In the introduction of the actual article introducing the study, Dwyer explains that language is not necessarily a verbal action. Rather, it is more of a psychological process which can be externally communicated in different methods. For instance, the MLU of a young, healthy child is normally associated with the number of verbal utterances within that child's sentences. However, when dealing with "language less species," (Dwyer, 1986), one must look beyond the pure verbal nature of language into a form of non-verbal communication -- sign language. Basically, verbal and non-verbal signing conveys the same general meanings, as well as the same general conceptions of mastery of a language. Therefore, the language capacity of a chimpanzee cannot be limited to the standards of pure verbal communication. They still are capable of the skills necessary for a conscious language.

Dwyer understands the concept that not all language methodologies come in verbal forms. Yet, the sentence is still the basic foundation of the conception of language, both verbal and non-verbal. Within the unit of the sentence come three underlying layers which formulate the context of the sentence. The phonological layer consists of the most phonetic blocks of language (Dwyer, 1986). The next layer is the morphological one, consisting of the linked morphemes within a sentence. Finally, the syntactic level is the overlying grammatical structure of the previous two combined in a larger sentence. Although these components are normally thought of as verbal aspects of language, they can also be represented in non-verbal, yet still grammatically correct forms of language. Therefore, the study aimed at comparing the MLU of both verbal and nonverbal children to that of a "language less chimpanzee." The methodology of this study pitted a normal child against a deaf child and chimpanzee. The levels of MLU were carefully observed as the young participants grew out of infancy. Starting at around nine months of age, researchers followed the individual youths until 48 months in order to get a scope of the general development of three separate groups involved in the study/

Although results showed variances within the verbal and deaf children, the biggest difference was within the max MLU of a chimpanzee. The researchers of this study spent long hours separating the different grammatical layers of one individual sentence. With this information, they gained a basic concept of the Medium Levels of Utterance associated with different language proficiencies of various language stages. By measuring the observations of MLU in normal and deaf children, compared to that of chimpanzees, researcher got an in depth glimpse into exactly how complex the foundations of language are within a chimpanzee. When compared to the MLU of a normal and deaf child, the level of proficiency within a chimpanzee levels out to about 1.5; far below the previously mentioned 4.5 MLU for an average eight-year-old.

However, the MLU levels were relatively similar for all three demographics until around the age of about 18 months, (Dwyer, 1986). This is when a change occurs in children who have the capacity for verbal communication as compare to the deaf children and chimpanzees. At the age of 32 months, talking children experience a dramatic increase in MLU as compared to deaf children and chimpanzees, reaching a MLU of 2.5 straight from the 1.5 of a 30-month stage. This dramatic increase is not seen in chimpanzees, which actually fluctuate between a 1.5-1.25 for the next several stages of language development. This data interpretation shows that chimpanzees are unable to reach the higher levels of syntactic communication seen in the more abstract speech of older children and adults.

The language efficacies of chimpanzees were further studied in a 1969 study focusing on teaching particulars of language to chimpanzees through the medium of sign language.

In this study, conducted by R.A. Gardner and B.T. Gardner in 1969 focused on teaching the complexities of sign language to chimpanzees of various ages. Researchers found that through intimidation and babbling training methods, various signs for words were eventually sifted in to the language capacity of the signing chimpanzee. After several trails, specific signs were added into the vocabulary of each chimp involved in the study. These signs were only added into to each chimp's vocabulary only if three separate observers acknowledged the chimp's prurience of that sign. This shows the mastery of the basic levels of sentence structure, which can later build up to larger utterance capabilities. However, these capabilities take a long time to increase, much longer in chimpanzees than human youths.