Shareholders of market research agency BrainJuicer are in for another windfall as the company unveiled its second special dividend for the year, along with a hike in its full-year payout, after profits more than doubled in 2013.Results were mostly fuelled by its two main businesses in the UK and US, while all of its other operations generated higher revenues, with the exception of Germany.The company, which paid a special dividend of 12p per share in October, representing £1.51m in cash, has said it will pay another special dividend of 12p due to its strong cash generation.Meanwhile, a 3p final dividend, along with the 0.9p interim dividend, has lifted the full-year payout to 3.9p, up 26% year-on-year.Pre-tax profit jumped by 135% in 2013 to £3.56m, as 17% growth in revenue to £24.46m was met with just a 7% increase in costs. The company said that its largest 10 clients by revenue grew by 61%."It's been emotional. 2012's flat result meant a miserable start to the year but the restored 17% revenue growth in 2013 was hugely uplifting to company spirits as well as financials," said Chief Executive John Kearon.BrainJuicer, which has no debt, ended 2013 with cash of £6.19m, up from £3.76m the year before."Looking ahead, we are planning more of the same, and believe we have the platform from which to deliver," said Chief Financial Officer James Geddes. "We have made a promising start to 2014, but as always, given our limited revenue visibility we cannot predict with any certainty how the year will unfold."The stock was 5% higher at 447p in early trading Friday, extending the year-to-date rise to 36%.BC