Defendant admitted negligence in an auto accident case. But the trial court correctly denied plaintiff’s motion for a directed verdict on causation. Defendant’s expert said only that the accident caused additional injury “if the plaintiff’s testimony is believed.” The jury could and did disbelieve plaintiff. Plaintiff could not complain on appeal about the wording of jury instructions since he invited any error; the jury instructions were jointly submitted by both parties. The motion for a directed verdict did not preserve any error in the wording of the instruction on causation. The issue of causation was properly presented to the jury. If plaintiff had an objection to the wording of the causation instruction, he needed to raise that objection in the trial court where it could be fixed easily and cheaply.