This is a cross-post of an article Dave Balter wrote here for Forbes. For more discussions and thoughts on the importance of humility in business leaders, check out HumilityImperative.com.

This article is by Dave Balter, the founder and chief executive of the Boston-based social marketing company BzzAgent, owned by dunnhumby ltd., where he is part of the global executive team. He is also a founder and the executive chair of the skill-testing platform Smarterer, and an investor or advisor to a dozen start-ups.

There’s a misconception that the most successful business leaders achieve greatness because they’re insanely smart—geniuses, even. You look at people like Mark Zuckerberg, Reed Hastings, and Warren Buffett, and it seems that might just be true. After all, they are more successful than their peers, and there’s no doubt they’re extremely sharp. Yes, they are smarter than you.

But the truth is different. Most highly successful leaders really aren’t the smartest people in any room. Rather, they have something that sets them apart. That something is sponge and stone. I’d argue that for any entrepreneur or leader, sponge and stone is the critical differentiator that defines his or her likelihood of success. (And I’d take success over smarts any day.)

In the business world, a sponge is someone who is tirelessly driven to seek and absorb new information. In general terms, this means someone who is highly curious, possibly even somewhat obsessive, about gathering data and learning from it. I don’t mean someone who simply stays up to date with TechCrunch and Mashable and loves to find articles to share via social media. Rather, a great sponge does three things:

1. Learns from mentors, advisors and peers. Sponges always surround themselves with people who can help them. They build and tap strong advisor networks. And for everyone they encounter, they ask questions, listen, and learn new things.

2. Studies heroes. A great sponge will typically have one or two individuals he or she considers heroes and will soak up everything possible about that person. Heroes don’t have to be business people. For instance, an early hero of mine was the Russian novelist Vladimir Nabokov. I found myself inspired more by his writing quirks than by his books or writing style. For instance, he was a serious lepidopterist, studying butterflies and moths (one he discovered is even named after him). I now value information obsession, which has helped me launch and build businesses. He also developed his novels using index cards, which he would arrange and rearrange. I find that writing speeches on cards helps me organize and reshuffle my points, if necessary. Nabokov compared the way he wrote to building a bird’s nest, and claimed that his notes made up a “kaleidoscopic arrangement of broken impressions.” I view my process of developing a company as establishing a set of elements that slowly form a bird’s nest.

3. Reads voraciously. Sponges tend to want to take in as much information as possible. I’m not talking about staying up to speed on 140-character Twitter blasts but rather consuming fully-developed content. And it doesn’t need to be about business. Sponges may devour fantasy or fiction. They may read instruction manuals front to back. It doesn’t matter. They feed on as much information as they can absorb.

But being a sponge is only part of what it takes to be a success in business. A business leader must also be a stone. There are two main characteristics of stone behavior: First, these determined individuals aren’t the smartest people in the room, but they work harder than everyone else. Secondly, stones have incredible strength of conviction. They are tough-minded and believe in whatever they are pursuing or doing, regardless of the challenges, hurdles, naysayers, and failures they encounter.

Stones do not have to barely scrape by and consider it a badge of honor to crash on a blow-up mattress in a start-up’s office. That happens sometimes, but it’s unnecessary. Consider Sidney Frank, who at the ripe age of 77 founded Grey Goose vodka. Already wealthy from previous ventures, he spent countless hours crafting one of the world’s most recognized brands, and he sold it five years later for $2 billion. I can bet you he wasn’t crashing on a blow-up mattress, but he did work relentlessly to make Grey Goose a hit.

Whether a business student or a successful entrepreneur, a Stone, like a Sponge, does three things:

1. Displays fearlessness—and even shamelessness. Stones don’t just work 24/7; they work every angle. Consider Rajat Suri, the founder of E la Carte, which makes tabletop ordering systems for restaurants. He once recommended that I eat at a sushi place in Palo Alto, because of a  rumor that Steve Jobs ate there. I went expecting little more than good sushi but, as luck would have it, Jobs walked in halfway through the meal. I thought that was cool, snapped a pic of him from afar, and left, eventually emailing Rajat to thank him for suggesting the spot. What did Rajat, tireless opportunist and stone, do? He dashed to the restaurant, secured a seat next to Jobs, and started toying around with an E la Carte device as the Apple chief looked over his shoulder. Then there is Jason Jacobs, of Fitnesskeeper. He is known to run entire marathons dressed up in a full-sized iPhone suit with his company’s RunKeeper application illustrated on the front. Yes, that’s going the extra mile.

2. Believes the impossible is possible. When my partners and I founded BzzAgent, my fourth startup, we were turned down by nearly 200 different investors. We were actually thrown out of agencies, and marketers wouldn’t try our word-of-mouth marketing product even for free. My family did an actual intervention, where they sat me down and tried to talk me out of pursuing the business. But we persevered, believing above all else that the concept of BzzAgent was possible. At last we persuaded some clients to come on board. Three years later we were profitable, on $3 million in revenue, and we raised our first round of outside capital. By 2004 BzzAgent was a real, growing company. But only because we believed, beyond all else. (Our tenacity paid off: BzzAgent was purchased by a unit of Tesco this year.)

3. Engages in multiple projects at once. This is perhaps the most polarizing behavior that a stone (and sponge) will typically exhibit. Sponges and stones, by their nature, have incredible curiosity and, often, ideas and energy to burn. For example, Elon Musk currently runs Tesla, but he also heads up SpaceX, a space exploration company. And Jack Dorsey is back at Twitter, but he still runs Square, a mobile payments start-up. One of the greatest errors an investor, advisor or mentor can make is to try to get a multitasking stone to focus on just one opportunity. Activity is likely part of that person’s DNA, and he or she is just trying to feed an immense appetite for knowledge, create new connections, and take advantage of ideas efficiently. We need to allow more entrepreneurs and leaders to pursue all the challenges that inspire them. If they’re the right people, they’ll know how to manage their time. They already work harder than normal people and, more important, their various projects will only accelerate their absorption of data and information. In fact, if someone isn’t interested in multiple concepts, is it possible that’s not a sponge and stone at all?

In all likelihood you’re probably not the next Sergey Brin or Jeff Bezos. But don’t despair. If you are starting a company, responsible for part of an organization, or making bets on entrepreneurs, you are most likely to succeed if you act as both a sponge and a stone—or if you align yourself with that kind of person.