Do you whistle while you work? Do you walk through the door of your workplace with a big smile because you're just so glad to be there? Are you worried that you're having too much fun at work and someone will find out and they'll stop paying you? Hey, if it's this much fun, why do they even call it work?

Would you believe corporations are spending considerable dollars to make their employees smile, or at least feel better about where they work?

According to Harvard University researcher Shawn Achor, employees who feel positive outperform employees who are negative in terms of productivity, energy levels, turnover rates and even health care costs. Achor is the author of "The Happiness Advantage" and he says optimistic  salespeople, outperform pessimistic salespeople by 37%.

Sales isn't the only field impacted by how you feel. Achor says he's seen across many industries and many jobs. He points out that doctors with a positive mindset are 50% more accurate when making diagnoses than those who are negative.

There are a number of companies that are investing in the happiness of their employees to increase both innovation and boost productivity. Smart Money actually has a list of some of the happiest companies to work for.

One of them is Google and its chief culture officer, Stacy Sullivan says "if you infuse fun into the work environment, you will have more engaged employees, greater job satisfaction, increased productivity and a brighter place to be."

Google has often been used as an example of a firm known for its forward thinking campus-like atmosphere and perks. For example, it offers its 23,000 employees onsite daycare, dry-cleaning, oil changes and free breakfast, lunch and dinner. Google even hosts "TGIF" staff meetings in which staffers can ask questions of the CEO.

Has all this paid off? Well, Google asked employees to use 20% of their work time on a project outside the scope of their jobs. This led to the creation of Gmail and Google Talk.

Some other companies that may not be as well known for their creative work atmosphere as Google  are beginning to find ways to increase workplace happiness. Financial firm UBS offers employees a nap room and a Friday beer cart. Beverage company PepsiCo encourages associates to get outside by offering them plots of land to start organic gardens.

According to the research, here are few companies along with Google and UBS who are spending money to make their employees happier.

Adobe offers employees positive psychology training; onsite cafeterias, fitness facilities and bocce courts; and 80 associations like knitting and book clubs bring employees together based on personal interests.

American Express encourages flexible schedules like telecommuting, job-sharing and compressed workweeks; employees are offered paid sabbaticals; gay partners receive health benefits.

At IBM researchers found the more social employees were the better they performed. Each additional e-mail contact added $948 in revenue so IBM launched a program to facilitate employee introductions to increase overall happiness.

KPMG invests in happiness training; allows employees to take partially paid leaves for up to 12 weeks; encourages flexible scheduling and formal mentoring programs.