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.

The camera on a 30mph limit junction of Newport Road  is catching an average of 71 speeding drivers every day.
A survey last year found a camera on the M60 in Greater Manchester caught about 26 speeding drivers per day.
The GoSafe partnership, which runs the Cardiff camera, said 99.5% of drivers at the site met the speed limit.
It said: "Motorists should comply with the relevant speed limit, which is there for a reason."
The body also insisted that placing cameras at a location was always "a last resort".
"The revenue from speeding fines is returned back to the government and not the partnership," said Chris Hume from GoSafe.
"There is a simple message - cameras are in place to save lives not to make money."
The camera was installed in 2012, but only went into fully commissioned operation earlier this year.
It has now notched up a staggering 13,624 penalty notices for speeding - and a further 146 drivers were caught for red-light offences.

Andrew Armstrong, 33, of Mossdale Road, Manchester, pleaded guilty to one count of rape at an earlier hearing.
The victim reported the rape to police in 2002 but the Crown Prosecution Service (CPS) decided no action should be taken.
A fresh investigation was launched in 2013 when the victim reported it again. Police said the woman had "suffered for years" and been ostracised by family.
The victim and a police officer handling the case were also threatened with rape via a text message on 12 May this year when Armstrong entered his guilty plea, police said.
The threat came from an unknown number and also contained a sexually-explicit photo.
A 59-year-old man has been arrested and bailed in connection with the incident.
Det Con Rachel Wood said: "This is one of the most harrowing cases I have ever dealt with during my years as a police officer."
She said the woman had "suffered for years" knowing she had been a victim of rape and was "further tormented" because she was "ostracised from her family who refused to believe her".
"Both the victim and myself were subjected to vile sexual threats so it is even more testament to the courage and bravery of this woman that she did not back down in the face of such disgusting threats and, as a result, Armstrong has been convicted of his appalling crime." the detective said.
"She has told me that the abuse she suffered at the hands of Armstrong ruined her life, to the point where she is paranoid the same thing will happen to her own children."
Armstrong was told he would remain on the sex offenders register for life.
Det Con Wood said she hoped the sentence at Manchester Crown Court would mean the victim could now "finally start to rebuild her life".
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.
[NEXT_CONCEPT]
A speed camera in Cardiff is the busiest in Britain - catching almost three times as many drivers each day as one on a busy Manchester motorway.
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A man who raped a 14-year-old girl in 2001 has been jailed for six years.