According to Dr. Karp, children in Tertia are raised by their own biological parents rather than an entire village claimed by Dr. Field because children talking more about their biological parents than others adults in the village during the interviews. Moreover, Dr. Karp argues that observation-centered method is not valid as the interview centered approach in the anthropology research. It is easy to come to the conclusion at the first glance. However, significant amount of evidence is needed to evaluate to the soundness of the argument. These evidence could weaken the argument, or the argument might turn out to be valid. To make the judgement, we need to collect more related information and then analyze to assess the argument.
The first evidence we need to collect is that where are the children being interviewed come from. The author claims that they have interviewed several children living in a group islands which includes Tertia. But, they might have not interviewed a single children that from exact Tertia. If in that case, the author's claim are strongly weakened since they do not even gained any useful information from children living in Tertia.
Another evidence we have to confirm is that whether Tertia has changed the raising mode of children in the last twelve years. Since Dr. Field has carried out the research 12 years ago, it is possible that, in Tertia, children are used to raised by an entire village but recently are reared more by they biological parents. If the modification of raising mode in the last twelve years confirms, the author's claim would also be weakened.
Last but not least, the evidence we need is about how the interview is carried out. What questions are asked by the interviewer? Are these questions mainly about the biological parents of these children? It is possible that children refers to their biological parents more that other adults in village because they are asked more questions with regard to their biological parents. In order to answer the parents-related questions, it is unavoidable to talk more about them. In this case, the author's argument is impaired.
The argument argues that the children in Tertia are more likely raised by their own biological parents. Nevertheless, we need more evidences regarding the origins of interviewed children, the modification of raising mode of the last twelve years, and the interview content.