The paper "Hallmarks of Biologically Controlled Behavior" is an excellent example of an essay on psychology. It has been recently established that linguistics, and especially the onset of speech in children, is determined biologically, and not out of any external stimulus or special training by the parents (Aitchison 70). For this theory to hold true, it must come in accordance with certain hallmarks that have been established to account for the biological onset of behavior, such as sexual characteristics and gait (Aitchison 70). One of such hallmarks, as described by Aitchison, is that biological behavior is not triggered by any external stimulus, however, the external environment must be rich enough for the behavior to adequately develop (Aitchison 71).
To put it more clearly, it states that although the onset of such behavior, in this case, speech, is not brought about by any external factors, the environment in which the child is developing must have the necessary stimuli to nurture the behavior (Aitchison 72), as external factors influence and limit the development of that particular behavior. This can be likened to the genetic predisposition to a height; it is greatly influenced by external factors.
Therefore, a normal child brought up by deaf and mute parents, as narrated by Moskowitz, would develop the linguistic ability but would fail to match the linguistic skills of his peers who have been brought about by normal parents due to a lack of practice and usage of the words and speech. Therefore, he would have a deficiency, either in the diction that he uses, or the sentence structure, the grammatical correlations (Aitchison 75), or any or all combinations of these factors, if no other external factor interferes, for example, he does not receive help or linguistic exercises from any other source.