Besides the observations conducted on the KE family, there are also other studies related to the FOXP2 gene and its purported link to language evolution. Various animal studies have been conducted to observe the possible effects of the FOXP2 in organism other humans. These studies usually utilize the technique of “knocking out” (in which genes are rendered non-functional) or “knocking down” (in which gene expression is reduced) genes so as to observe any resulting effects due to the absence or the reduction in expression of a particular gene. This can lead to further understanding of the function of a particular gene by a comparison with organisms with normal functional genes.  A study conducted on zebra finches (a type of songbird) had shown that FOXP2 expression increases in the Area X region of its basal ganglia. By knocking down FOXP2 in these songbirds, it can be observed that there is inaccurate and incomplete imitation of a song. The abnormality of song learning by these birds have also been compared to the learning of words by children afflicted with DVD. (Haesler, Rochefort, Georgi, Licznerski, Osten & Scharff, 2007)