The trial court awarded custody of the four children to the father. The court of appeals reversed, awarding custody of the three youngest children to the mother and remanding the issue of the oldest child’s custody to the trial court for reconsideration. We affirm.
In April 1987, after 10 years of marriage and four children, Steven and Diane Max-field separated. The couple had then been living in Verndale, Minnesota, Steven’s hometown, for 3 years. Two months after separating, in June, Diane and the four children returned to Wilkes-Barre, Pennsylvania, Diane’s hometown, ostensibly for a visit, but actually because Diane had decided to end the marriage.
Unable to persuade Diane to return to Verndale, Steven filed a separation action requesting custody of the four children. Diane countered with a dissolution petition and requested custody of the children. A year later, in July 1988, the case was called for trial. During that year the children were with their mother in Pennsylvania. At the time of trial Steven and Diane were both 34 years old. The three youngest children, Jacinta, Therese, and Aleshia, were 2, 4, and 8 years, respectively. The oldest child, Jeremiah, was 10.
The trial judge heard the testimony of the parties and their witnesses and received in evidence reports from the social services personnel of Luzerne County, Pennsylvania, and Wadena County, Minnesota. The court made the following (here abbreviated) findings of fact:
1. While the family was together in Verndale, Steven was away at trade school and at work, and the care of the four children, for the most part, fell to Diane.
*2202. Diane was home alone with the children most of the time. She had no car, no phone, few friends, and little money. She felt isolated in the small rural community and became depressed. Her housekeeping was seriously substandard. Diane sought counseling from Wadena County Social Services for her loss of self-esteem and self-confidence. In April 1987, at Diane’s request, Steven moved out of the house and lived in a pickup camper in a woods on a friend’s property. Steven spent time with the family, however, virtually every weekend.
3. About the end of June, Diane returned to Pennsylvania with the four children. She told Steven it was only for a visit, and Steven along with Diane’s mother paid for the air fare; in fact, Diane intended to stay in Pennsylvania. Diane kept her residence a secret and Steven was almost totally cut off from contact with his family. Steven did, however, visit with the children in Pennsylvania over the Thanksgiving weekend, and in June 1988 for a few weeks prior to and during trial, the children lived in Steven’s home.
4. Diane appeared to be doing a satisfactory job of homemaking and housekeeping in her subsidized housing apartment in Pennsylvania, as reported by the social worker. The two oldest children did well in school but Jeremiah felt picked on.
5. Steven and Diane had met and were married while Steven was in the Army. When Diane returned to Pennsylvania she met a much older man, through an advertisement, and planned to marry him. (This man testified at trial.) There was some evidence that Jeremiah did not like this proposed marriage. The proposed marriage would introduce an element of “disequilibrium” into the family setting, as the children would move once again. (Since the trial these marriage plans have been abandoned.)
6. Jeremiah and Aleshia, the two oldest children, were interviewed by Dr. Ralph Scheer, a psychologist, who also serves in the Wadena County guardian ad litem program. This was pursuant to an arrangement made by counsel and the court. Jeremiah told Dr. Scheer the housing project was noisy, with much bad talk, and the children missed their pets on the farm. Dr. Scheer attempted to elicit the two children’s custodial preference without asking them directly to choose between the parents. The two children expressed a preference for Yerndale.
7. Dr. Scheer felt that Aleshia, then 8, was not mature enough to express a valid preference. He did feel that Jeremiah definitely preferred a small-town environment and life style, which could be interpreted as the boy’s preference to live with his father. Even though Jeremiah had done well in school in Pennsylvania, he felt more “at home” in Verndale.
8. Steven now has a full-time, permanent job. For the time being, Steven’s mother helps with the children in the morning before Steven goes to work and takes them to the babysitter for the day. At the end of the day, the grandmother picks up the children and takes them to Steven’s home and waits until Steven gets home from work. Steven has demonstrated that he is able to provide for the needs of the children.
After making the foregoing findings of fact, the trial court then made the following (here summarized) conclusions of law:
(1) When the parties separated in April 1987, Diane was the primary parent as defined in Pikula v. Pikula, 374 N.W.2d 705 (Minn.1985). More than a year has gone by, however, between the time when the parties separated (April 1987) and the date of trial (July 1988), and, therefore, “it is appropriate for the Court to consider the events and developments which occurred in that intervening period * * *.”
(2) The Pikula presumption of primary parent does not apply when a child is old enough and mature enough to express a meaningful custodial preference. Here, both Aleshia and Jeremiah expressed a preference, and Jeremiah at least was of an age and maturity to express a valid preference. “The presumption created by Pikula does not apply.”
(3) In considering the best interests of the children under Minn.Stat. § 518.17, *221subd. 1 (1988), a consideration of the evidence “points unmistakably toward an award of custody in favor of Steven.” In this connection:
(a) Both of the older children prefer Verndale.
(b) One or more of the children have a particularly close relationship with the paternal grandmother.
(c) While the report cards of the two oldest children suggest “things out east were perhaps not as bad as described by the children,” nevertheless the children expressed to Dr. Scheer concerns and difficulties in adjusting to home, school and the community in Pennsylvania.
(d) An award of custody to Diane (if she remarries) presents the prospect of another change and a lack of continuity with respect to their environment in Pennsylvania. Verndale appears to present a more permanent custodial home.
(e) The expressed preference of the two older children for Verndale (even after being gone for over a year) “makes clear the degree to which the children feel a strong emotional bond with their father. Thus * * * an award of custody to the father would be consistent with maintenance of continuity and stability for the children with respect to emotional and psychological attachment to the primary psychological parent.”
(f) There is a strong likelihood that Diane, if awarded custody, would restrict Steven’s contacts with the children, destroying any meaningful relationship the father might hope to have with the children.
As noted, the trial court awarded custody of the four children to the father. On appeal, the court of appeals reversed, awarding the three youngest children to the mother and remanding the question of Jeremiah’s custody to the trial court. Maxfield v. Maxfield, 439 N.W.2d 411 (Minn.App.1989). We granted the father’s petition for further review.
The issue, as we see it, is whether the trial court’s best interests analysis was correctly applied.
Discussion
Our concern here is not with the findings of fact but with the conclusions drawn from those facts. Particularly in cases of this kind, where the trial court is weighing statutory criteria in light of the found basic facts, the trial court’s conclusions of law will include determination of mixed questions of law and fact, determination of “ultimate” facts, and legal conclusions. In such a blend, the appellate court may correct erroneous applications of the law. As to the trial court’s conclusions on the ultimate issues, mindful of the discretion accorded the trial court in the exercise of its equitable jurisdiction, the reviewing court reviews under an abuse of discretion standard. See, e.g., Berndt v. Berndt, 292 N.W.2d 1, 2 (Minn.1980). When the trial court’s treatment of mixed questions of law and fact and its treatment of the ultimate issues may involve a misapplication of the law, the appellate court should carefully review the trial court’s “explanation of] how the factors led to its conclusions and to the determination of the best interests of the child.” Minn.Stat. § 518.17, subd. 1 (1989).
Here the trial court, quite correctly, concluded that Diane was the “primary parent” of the four children at the time the parties separated. Implicit in this conclusion was a finding that the children have a psychological and emotional intimacy with the parent who has been primarily responsible for their nurture and care.1 The trial court also concluded, however, that the Pi-kula custodial preference for the primary parent was not applicable because the custody determination was being made some 15 months after the parents had separated. The trial court relied on Sefkow v. Sefkow, 427 N.W.2d 203, 212 (Minn.1988), wherein we said, “Only if this [separation] date is *222reasonably close to the actual trial does the Pikula analysis have any viability.” In Sefkow, however, the parties had been litigating custody for 4¾⅛ years after separation. In this case, not only was Diane the primary parent at the time the parties separated but she continued to be the primary parent of these very young children up to the time of trial. There is no finding by the trial court that Diane is unfit to be custodian. If the Pikula preference applies, custody of the children, at least the three youngest, it would seem, should have been awarded to Diane.
Steven argues, however, that deference to the Pikula preference should not be given because the 1989 legislature, albeit since the trial, has eliminated that preference.2 Apparently the 1989 amendments were a reaction to the mechanical way in which Pikula was being applied. It was never intended, however, that custody be awarded to whomever scored the most points on the Pikula caretaker scale (who bathed the child, who put the child to bed at night, etc.). It was recognized that other indicia of a child’s best interests, although difficult to evaluate, were “plainly relevant,” Pikula, 374 N.W.2d at 712, and that, in the final analysis, the aim was to place the child too young to express a preference where that child might best have the emotional security and nurturing environment so vital to the child’s life and development. Later, in Sefkow, we observed that the primary caretaker doctrine is an “extension and refinement of the statutory criteria” and that “the statute mandates a multifaceted inquiry into ‘all relevant factors’ * * *.” Sefkow, 427 N.W.2d at 212.
Sefkow, in other words, cautioned against applying Pikula mechanically, and the trial court, with Sefkow in mind, correctly conducted a “multifaceted inquiry” into “all relevant factors.” Our concern is not with the trial court’s approach but with the manner in which this best interests approach was applied. In discarding the presumption set out in Pikula, the trial court also discarded (or at least severely discounted) the evidence on which that presumption or preference was based, namely, Diane’s status as the primary parent. The failure to give any credit for Diane’s primary parent status, it seems to us, skews the trial court’s best interests analysis. This, too, was the conclusion of the court of appeals. Maxfield, 439 N.W.2d at 416 n. 3.
For example, the evidence is undisputed that all four children love both their father and their mother. As Dr. Scheer put it, “I saw evidence of real love for both the mother and the father.” From this the trial court concluded an award of custody to the father would be consistent with an attachment to the primary psychological parent. This conclusion, however, is inconsistent with the trial court’s determination that the children’s mother is already their primary parent. This inconsistency is never explained. Nothing occurred during the year between separation and trial to suggest Diane ceased to be the primary parent.
The trial court felt that the expressed preference of the two oldest children for the Verndale environment should be given great weight. It followed then, thought the trial court, that rather than split the family, all four children should be with the father. Yet this reasoning is difficult to reconcile with the fact that the four children are also devoted to their mother, that they were doing relatively well in Wilkes-Barre, and that it is the mother who has primarily cared for the children all their years up to the time of trial.
Here was a “traditional” marriage with Diane at home with the children and Steven at work full time away from the home. Diane, lonely and isolated at Verndale, be*223comes listless and depressed. She returns home to Pennsylvania where her emotional health improves.3 Her homemaking and housekeeping practices now in Pennsylvania are, as the trial court found, satisfactory. While the trial court noted the two oldest children (or at least Jeremiah) preferred living in Verndale, neither Verndale nor Wilkes-Barre was found by the trial court to be an unwholesome environment. Diane’s conduct in denying Steven contact with the children when they were in Pennsylvania is not to be condoned, but the court can take measures to reinforce her assurance given at trial that Steven will have access to the children. The trial court’s concern that Diane’s proposed remarriage would be disruptive has been mooted.
In applying a best interests analysis, we recognize much must be left to the discretion of the trial court. Some statutory criteria will weigh more in one case and less in another and there is rarely an easy answer. Yet as our pre-Pikula cases illustrate, the golden thread running through any best interests analysis is the importance, for a young child in particular, of its bond with the primary parent as this relationship bears on the other criteria, such as the need for “a stable, satisfactory environment and the desirability of maintaining continuity” and “the mental and physical health of all individuals involved.” Rosenfeld v. Rosenfeld, 311 Minn. 76, 81, 249 N.W.2d 168, 170-71 (1976). Usually this relationship “should not be disrupted without strong reasons * * *.” Berndt, 292 N.W.2d at 2. Here we conclude that the trial court exceeded the proper bounds of its discretion in awarding custody of the three youngest children to Steven. Their best interests are served if custody is with Diane.
Jeremiah is old enough and mature enough to express a preference where and with whom he wishes to live during his approaching teen-age years. The appeals panel felt that Jeremiah had expressed only a geographical preference, not a custodial preference, in his interview with Dr. Scheer. We are not prepared to say that Dr. Scheer’s indirect approach to custodial preference was inappropriate under the circumstances of this case. Here, a geographical preference would seem to determine custodial preference, a fact of which Jeremiah could not have been unaware. This, too, was the trial court’s view. In any event, we agree that the question of Jeremiah’s custody should be remanded to the trial court for reconsideration as ordered by the court of appeals. Jeremiah must now, in expressing a preference, consider the fact that living in his father’s home would mean separation from his three younger sisters. Split custody is not favored. Yet, as someone has said, children come into this world one by one, and in deciding their future, this, too, must be decided one by one. We must leave this difficult issue to the trial court.
We affirm, therefore, the court of appeals’ decision awarding custody of the three youngest children to Diane and remanding Jeremiah’s custody to the trial court. Part III of the court of appeals’ decision on matters of property division and child support was not appealed and remains undisturbed. The trial court will also, of course, have to consider the important matter of visiting rights by the noncustodial spouse and the protection of those rights.
Affirmed.
YETKA, J., dissents with opinion in which POPOVICH, C.J., and KELLEY, J., joins.. As we noted in Pikula, 374 N.W.2d at 711, in Bemdt we held "the enumerated statutory criteria, even absent consideration of other relevant factors, mandate that, when the evidence indicates that both parents would be suitable custodians, the intimacy of the relationship between the primary parent and the child should not be 'disrupted without strong reasons which relate specifically to the [primary] parent’s capacity to provide and care for the child.’”
. The 1989 legislature amended Minn.Stat. § 518.17, subd. 1, to provide that "the child’s primary caretaker" and "the intimacy of the relationship between each parent and the child” are to be factors in deciding the best interests of the child and further mandated that none of the statutory factors enumerated may be used to the exclusion of all the others. Act of May 25, 1989, ch. 248, § 2, 1989 Minn.Laws 834, 835. In other words, the fact that one parent may be the primary caretaker does not necessarily control who gets custody. All relevant factors must be weighed in the balance.
. While social worker reports often need to be considered with caution, the Luzerne County social worker reported, "Mrs. Maxfield’s housekeeping standards were excellent. * * * I also believe that her emotional state of mind had a lot to do with her lack of motivation to clean her home [in Verndale]." The report also concludes: “At this time Dianne Maxfield is providing her children with the love and stability that they need.”
Compare Berndt v. Berndt, 292 N.W.2d 1, 2 (Minn.1980): "Respondent’s previous behavior, which, in the trial court’s opinion, demonstrated a lack of stability or judgment on her part, has no bearing on [her] present capacity to provide for the physical and emotional needs of her daughter and was improperly considered by the trial court in reaching its custody decision.”