Eddie Jones believes England's lack of aggression at the start of their Six Nations title defence may be the result of playing matches behind closed doors.
England launched the 2021 edition with a lacklustre 11-6 loss to Scotland as their oldest rivals won at Twickenham for the first time since 1983.
And despite not being at their best, England ran in six tries to beat visitors Italy 41-18 last weekend.
Both matches were played without spectators because of coronavirus restrictions, a situation that is set to continue when England travel to Cardiff for a third-round clash with title contenders Wales on February 27.
Meanwhile, England coach Jones believes a study into Austrian Bundesliga football team Salzburg showing the impact of playing behind closed doors could hold lessons for his side as well.
That research indicated a fifth fewer "emotional situations" take place when stadiums are empty of fans, leading to a reduction in on-field flashpoints and arguments, with Jones saying the absence of spectators was having a similar impact on rugby union as well.
"Most teams are a bit up and down at the moment. The arousal level is the thing we are looking at most," said Jones, an Umbro ambassador.
"Games are tending to be less aggressive generally in rugby and it has been the same in football," the former Australia and Japan coach explained.
"There is research that shows the arousal level has dropped and that the type of play and the type of behaviour has been less aggressive. In our sport that is a particularly important area.
"We have tried to investigate that. We don't have any solutions at the moment but that is the thing we are looking at most."
Jones added: "If you look at our first performance against Scotland, we lacked our normal aggression, we lacked our normal go-at-them type of game. We were a little bit better against Italy, but still not where we need to be."
England captain Owen Farrell has been well below his best so far this Six Nations, possibly as a result of lacking match sharpness following Saracens' relegation for Premiership salary-cap breaches to a second-tier Championship whose start has been delayed by Covid-19.
Farrell's place is under no immediate threat but Jones accepts there's room for improvement from the centre-cum-fly-half.
"He's working very hard to get his game back to the standard that he wants and we want," said Jones of Farrell. "There's no doubt he'll get back there.
"There could be something going on at home, there could be something going on at his club that's affecting him, we don't know.
"He's not at his best at the moment and we're working really hard to make sure he gets to his best."