The 35-year-old endured the worst season of his F1 career in 2014 with a solitary fourth place in Belgium his best result.
The Finn, who was Ferrari’s last world champion back in 2007, was well-beaten by team-mate Fernando Alonso, finishing 106 points and six places adrift in the drivers’ standings.
He struggled with the handling of the Ferrari, which did not suit his style of being heavy on the front tyres and gentle on the rear.
But Raikkonen seemed happier during 2015’s opening test at Jerez and has said that he is feeling more comfortable with the car.
And Arrivabene says he has noticed a change in Raikkonen’s typically uncommunicative persona, joking that the Finn must be feeling “sick” because he’s smiling so much.
“He had his problems [last year],” said Arrivabene. “Problems because he was not feeling the car, especially the front.
“It was not a car that was adapted to the style of Kimi.
“He is demonstrating that these days, he is feeling the car better and he is smiling.
“This is very, very strange. It is the real scoop of the weekend.”
Arrivabene added that Raikkonen’s behaviour in the garage has also been different to 2014 so far during testing.
“Kimi was also on the ground to move the car and try to adjust something,” he said.
“I asked him: ‘What are you doing?’ He said ‘I was a mechanic’.
“This is the atmosphere in the team, all the guys around him were surprised to look at him and to hear him talking and talking and talking.
“I thought he was sick but he is not. It is just enthusiasm and I am sure this year Kimi can demonstrate his level.
“Kimi is very motivated and he is getting very, very well with [new team-mate] Seb [Vettel] and this is great.”
[ Source: autosport.com ]