Cambridge University Press is analysing media coverage during Brazil 2014 and scoring 'confidence levels' out of 100.
The score rises and falls dependent on the words used to describe England.
Confidence was measured at 38 after the 2-2 draw with Ecuador on 4 June and 40 following the 0-0 draw with Honduras on 8 June but rose to 77 a day later.
England's current rating is 70, going into the game in Manaus, according to the Cambridge Confidence Index.
Researchers have analysed and assessed millions of words from a wide range of media sources over the past two weeks.
Cambridge University Press's Dr Claire Dembry said: "The breadth of sources means we're able to give a unique insight into the mood surrounding the England team.
"It's interesting to see that the nation is in confident spirits ahead of the Italy game, despite some fairly lacklustre performances against Ecuador and Honduras."
England fans have voted with their money such is the confidence factor and England have been backed from 2/1 shots to 6/4 favourites with Betfair to win their opening game. Italy have drifted to 11/5 on the news that their skipper and goalkeeper Buffon misses the game through injury. The Italian stopper is a key component in the Italian side with over 130 caps.