If you want to negotiate with someone it may be better to schedule the meeting in the morning. An article in the NYTimes suggests that people are more likely to cheat or deceive as the day wears on and depletes their brain:
“This so-called morning morality effect results from ‘cognitive tiredness,’ said Isaac H. Smith, an assistant professor at the Johnson Graduate School of Management at Cornell University and co-author of the article with Maryam Kouchaki, an assistant professor at the Kellogg School of Management at Northwestern. ‘To the extent that you’re cognitively tired,’ Dr. Smith added, ‘you’re more likely to give in to the devil on your shoulder.'”
Click on the link below for descriptions of the experiments performed.