(Parenthetically, one thing I had not been aware of is how low actors' pay can be in theater. It is not unusual for an actor, even in a lead role in a play, to get $500 for the run. The run includes not just the two or three weeks of performances but also the one or two months of rehearsals, often in another city. This post, however, is about an experience he had in movie acting.)
The Screen Actors Guild (SAG) has local offices around the country. (Since this happened, SAG has merged with the American Federation of Television and Radio Artists (AFTRA)). The production company in the case I'm about to tell wanted Robert for a lead role. Near the location where the movie was to be shot, the local SAG, knowing that the SAG wage rates might sink the project, let it be known informally that it would look the other way if the union members agreed to lower pay. It pointed out that, however, if that happened, SAG would be unable legally to enforce any of the standard SAG terms, so the actors were on their own. One of the important SAG terms is on overtime pay.
In the negotiations before the actors agreed to be in the film, the producer asked the actors if they were willing to work overtime without overtime pay. A typical day was 8 or 10 hours (Robert doesn't remember which in this case) and actors were paid a day rate. So if you worked overtime, you were paid zero for that extra time. Robert was aware that that gave the production company very little incentive to care about having the actors on set for more than the standard day. So he didn't agree to no overtime pay. That's where his understanding of incentives was useful. They hassled him about it too, but he stuck to his guns. However, a boy and girl friend acting pair did agree to no overtime pay. Every day when Robert showed up for work at his call time, the boy and girl friend had already been called to set. Every day, when he had been released, the boy and girl friend remained for an extra hour or two.