Does commentary on the meaning of reasonable doubt during closing arguments confuse the jury?

Each appellant argues that commentary on the meaning of reasonable doubt during closing arguments may have confused the jury. We review for abuse of discretion the district court's decision to allow the jury to consider comments made in closing argument after an objection is made. United States v. Diaz, 961 F.2d 1417, 1418 (9th Cir.1992). If no objection to the comments is made at trial, then review is for plain error. See United States v. Feldman, 853 F.2d 648, 652 (9th Cir.1988), cert. denied, 489 U.S. 1030 (1989).