It found that turnout for the September ballot could be somewhere between 70% and 80%, with those who are confirmed Yes voters slightly more likely to say they will make it to the polls.
The proportion of those who are clear that they will vote Yes and who state that they are more than 50% likely to vote is four percentage points higher than the equivalent proportion for No voters, standing at 90% compared with 86%.
The gap grows to 7% when those who are undecided but are leaning towards a Yes or a No vote are added, standing at 90% on the Yes side compared with 83% for No.
Turnout and voting intentions for the referendum were examined by researchers at social research institute ScotCen.
They used data from the 2013 Scottish Social Attitudes survey, which questioned 1,497 people between June and October 2013.
Looking at only undecided voters - who represent around a third of those surveyed - 91% of those leaning towards Yes are more than 50% likely to vote, compared with 73% leaning towards No.
ScotCen's analysis says: "If we take into account each Yes and No respondents reported probability of voting, it is enough to add two points to the Yes side's estimated share of the vote."
Dr Jan Eichhorn, research fellow at Edinburgh University, who compiled the data, said: "While the overall turnout in the referendum is expected to be high, around 70%- 80%, there could still be a higher turnout amongst Yes than amongst No supporters. In a tight race, this could be crucial."
John Curtice, research consultant at ScotCen, said: "The proportion of those who say they are likely to vote has increased as the campaigns have developed.
"Far from putting people off, the campaigns are resonating with the public. But both campaigns evidently still need to make sure their supporters participate in the referendum come polling day."
Yes Scotland chief executive Blair Jenkins said: "This suggests that more and more people are listening to the real facts and figures instead of 'Project Fear' scaremongering, they realise that, of the two futures facing their country, they are more likely to come out and vote for independence."
Liberal Democrat leader Willie Rennie said: "As leader of the Liberal Democrats I am working hard to secure the result I know the majority of people in Scotland wish to see. That is a stronger Scotland within a federal UK.
"But Scotland's future is not just about party politics. We want to appeal to everyone who believes that Scotland is served better when we work together as part of the UK.
"This is a positive vision which we mustn't let slip from our hands because of apathy alone. With five months to go until the referendum, it is game on."