A great actor knows how to command a strong physical presence when they walk on set. And though it’s not necessary for every role, an actor’s ability to do a spot-on impression of someone else never hurts their credibility. As dialect coach Erik Singer illustrates in this video for WIRED, the adopted dialects we hear in some of cinema’s most iconic films are sometimes even more impressive than we realize.

After looking at clips of famous performances, like Daniel Day-Lewis’s Oscar-winning portrayal of the 16th president in Lincoln (2012) and fellow Oscar-winner Jamie Foxx’s interpretation of Ray Charles in Ray (2004), Singer broke down everything from their facial movements to their treatment of certain sounds and phrases. Among the actors he praises are Natalie Portman for her take on Jackie Kennedy’s unique way of speaking in Jackie (2016) and Michael Fassbender in Steve Jobs (2015), a biopic of the Apple founder. But not all of his comments are glowing: Even for performances that he deems mostly accurate, like Joaquin Phoenix’s portrayal of Johnny Cash in Walk the Line (2005), he’s able to pick out the most minor discrepancies.

After watching his verdicts below, you can check out Singer’s earlier video of his thoughts on actors adopting foreign accents (not necessarily those of people in real life).

[h/t WIRED]