What is the standard required for a joint work to be copyrightable?

Various circuits of the federal courts in the United States have come to differing conclusions as to the standard required in order to meet the contribution element. The more recent trend in the cases is towards the acceptance of the copyrightable approach. In Childress v. Taylor, 945 F.2d 500 (2d Cir. 1991), where the defendant actress claimed to be a joint author with the plaintiff playwright, the court struggled with the issue of why the contributions of all joint authors needed to be copyrightable. The court, at p. 506, stated, "An individual creates a copyrightable work by combining a non-copyrightable idea with a copyrightable form of expression; the resulting work is no less a valuable result of the creative process simply because the idea and the expression came from two different individuals." Notwithstanding this view, the court endorsed the copyrightable approach, stating at p. 507: The insistence on copyrightable contributions by all putative joint authors might serve to prevent some spurious claims by those who might otherwise try to share the fruits of the efforts of a sole author of a copyrightable work, even though a claim of having contributed copyrightable material could be asserted by those so inclined. The court summarized at p. 507: It seems more consistent with the spirit of copyright law to oblige all joint authors to make copyrightable contributions, leaving those with non-copyrightable contributions to protect their rights through contract.