In Harris v. Harris, 149 Vt. 410, 546 A.2d 208 (1988), the mother, who did not prevail in the custody dispute in the trial court, argued that the trial judge could not consider that she was living out of wedlock with a man, without expert testimony to show the effect on the best interest of the child. The Court rejected that argument as follows: While the expert testimony would have been helpful in this case, we agree with the trial court that the evidence fell in an area where the court could evaluate it without expert testimony. Such evaluation was expected under the language of 665(b)(7). We concur with the Supreme Court of Kentucky which, facing a similar statute and similar evidence, said: A trial judge has a broad discretion in determining what is in the best interests of children when he makes a determination as to custody. In many instances he will be able to draw upon his own common sense, his experience in life, and the common experience of mankind and be able to reach a reasoned judgment concerning the likelihood that certain conduct or environment will adversely affect children. It does not take a child psychologist or a social worker to recognize that exposure of children to neglect or abuse in many forms is likely to affect them adversely. Many kinds of neglect or abuse or exposure to unwholesome environment speak for themselves, and the proof of the neglect or abuse or exposure is in itself sufficient to permit a conclusion that its continuation would adversely affect children. We also think the trial court is not precluded from consideration of circumstances where the neglect, abuse, or environment has not yet adversely affected the children but which, in his discretion, will adversely affect them if permitted to continue. In other words, a judge is not required to wait until the children have already been harmed before he can give consideration to the conduct causing the harm. Krug v. Krug, 647 S.W.2d 790, 793 (Ky. 1983). Accordingly, we hold that the trial court did not err in accepting the evidence and relying on it in the custody determination. (149 Vt. at 416-17, 546 A.2d at 212-13.) The Court established that the primary care giver factor "should be entitled to great weight unless the primary custodian is unfit." Although the Court declined to create a per se rule in favor of the primary care giver, the result in Harris requires "the court to look carefully at the desirability and impact of changing the primary custodian." Id.