TORONTO • Actor Jesse Eisenberg has a reputation for not suffering fools, for witheringly knocking down any stupid questions that are put to him.

In the 12 years since his breakout role as a callow, Kafka-referencing teen in director Noah Baumbach's The Squid And The Whale (2005), he has made his name with characters who are - or at least believe they are - the smartest person in the room: the snarky theme-park attendant in Adventureland (2009); the college kid bon-moting his way through the apocalypse in Zombieland (2009); and, of course, his sociopathically still performance as Facebook founder Mark Zuckerberg in The Social Network (2010), for which he received an Oscar nomination for Best Actor.

In person, speaking at the Toronto International Film Festival, the 34-year-old is disarmingly alert - quick to answer a question with a question - but never difficult or obtuse.

There is a fine seam of comic self-doubt running through his patter, and today, he is mostly just buzzing with ideas.

He is fascinated and appalled by the high-speed, high-frequency trading depicted in his upcoming film, The Hummingbird Project - where computer algorithms buy and sell stocks in the blink of an eye - but can relate to people such as his character Vincent, "so caught up in the pursuit that they lose any sight of any kind of ethical considerations".

"It's like when you're acting in a movie and there's a tree in the middle of the shot," he says. "The first thought of every person on a crew is: 'We'll just cut down the tree', rather than move the camera. Because when you're working on a movie, you think that the world needs to see this story, that it's so important, and of course the tree is irrelevant in the grand scheme of that.

"Only when the day is over and you look back at it, do you think: 'Well, I really don't think we needed to cut down the tree to do this horror-comedy…'"

If Eisenberg can see the forest for the trees when it comes to Hollywood, it is probably because acting is not the only thing he does.

He has written a number of plays, as well as humour pieces and short stories for The New Yorker and McSweeney's.

Most significantly, he has recently become a father for the first time. He and his wife had a son last year, a development that has put his day job into perspective.

"I don't think I care any less about my work or like it any less - in some ways, I like it more because it's my one opportunity to get away for a few minutes," he says. "But I do think if humans have the unconscious desire at all to be immortal, maybe that feeling of immortality is being accounted for in another way through their children, rather than through their work, so maybe it takes the pressure off that."

Having a child has been instructive, not least in terms of the feelings of anxiety that have been a constant in his life since his childhood.

Eisenberg has spoken about being diagnosed with obsessive-compulsive disorder, social anxiety and depression; last year, he recorded a video in which he offered advice to his younger self on overcoming anxiety.

"Just selfishly, having a child is the best thing anyone can do for his own anxiety, if your anxiety is like mine, which is, to say, based in fantasy," he says. "Because I spent the first 30 years worrying about things that were invisible, and now I get to worry about something that's visible, and there's nothing that's more mentally healthy than worrying about something that's actually existing in the world, rather than worrying about something that doesn't exist at all."

In The Hummingbird Project, the role Eisenberg would normally be expected to take - awkward genius - is filled instead by Swedish hunk Alexander Skarsgard, who plays Anton, a tech savant with game-changing ideas and a tendency towards introverted awkwardness. (Skarsgard is virtually unrecognisable in a bald cap and a prosthetic pot belly.) Eisenberg plays Anton's striver cousin, the man who facilitates his genius.

Together, the pair devise an ambitious plan to lay a fibre-optic cable from Kansas to New Jersey, under rivers, mountains and millions of homes.

The aim of this quixotic endeavour is to receive stock-market information one millisecond faster than the high-frequency traders on Wall Street, a tiny advantage that could net Vincent, Anton and their clients hundreds of millions of dollars.

Canadian director Kim Nguyen films all this as a high-stakes caper: the pair race against time to get their cable operational and face a formidable, power-suited rival in Salma Hayek's stock-exchange boss. Anton is the brains of the operation, with Vincent providing the unrelenting drive and gift of the gab.

Nguyen sent Eisenberg the roles of Anton and Vincent, and Eisenberg opted for the one that seemed most out of character.

"I just knew I didn't want to play the socially aloof genius because I'd done that, and also because I liked Vincent more," he says. "The only thought I had was to play the dumber hustler."

Despite the attempt to play against type, early reviews of The Hummingbird Project have noted that Vincent has an inherent Eisenbergness: the pointed staccato delivery, the restless physicality and the sardonic worldview we have come to expect in his performances.

That seems a touch unfair.

Vincent, for reasons that become apparent in the film, is a more heroic and poignant figure than Eisenberg's previous creations, but by now, it is a characterisation with which the actor has become familiar - and even comfortable.

"You just want to keep things interesting for yourself by playing characters that seem different, but you can't control how an audience perceives you," he says with a shrug.

"As long as I get to do things I like, I don't really care."

GUARDIAN