A poker face could prove useless during negotiations.
Poker faces might not be that useful
Experts at Nottingham Trent University have found that being pleasant and facially expressive makes a person more likely to close a deal.
The findings are based on an analysis of over 1,500 conversations focusing on muscle movements in the face - including smiles, eyebrow raises and nose wrinkles - which found that facially expressive people were considered to be more likeable and socially successful.
The boffins think this research could reveal why humans have more complex facial expressions than other species.
Professor Bridget Waller, who led the study, said: "Our comparisons between humans and other primates show that humans produce more facial movement on the whole and have more expressive faces.
"Being expressive make you more likeable, which might make it easier to live in social groups, which is a clear evolutionary advantage."