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."
Words such as "progress",  "strong" and "joy" have increasingly been used by players, coaching staff and fans.
Midfielder Adam Lallana, 26, and 18-year-old Luke Shaw, who are both seeking to leave Southampton, have been described more positively than any other England player.
Neymar, who scored twice in Brazil's 3-1 victory over Croatia, was the most talked about player after the opening match.
"Controversial" was identified as the word of the day following the disputed penalty for Brazil's first goal and anti-World Cup protests in several host cities.
Cambridge will track positive and negative indicators throughout the tournament, in order to measure changes in the perceived confidence in the England team.
Confidence in the England team is high ahead of Saturday's opening World Cup match against Italy, according to a study of words relating to football.