When I read what the motivators were for the experiment in the below article, I have to say the voucher for a free pizza definitely spoke to me on a personal level #pizzaislife after all, and so I thought this would most likely be the same for quite a few people and was surprised to see that this wasn't the case. If you have a few spare moments i'd definitely recommend having a read of this interesting little piece about employee motivation from one of the upcoming TED Books. 

'Just think: If the promise of a simple text message from the boss can increase productivity, can you imagine what real, sincere and authentic praise would do?'