The Emmanuel Adebayor "smileometer" has quickly become a pertinent gauge of the atmosphere around White Hart Lane.
"He comes in with a smile on his face and he runs around like a two year old in training," Harry Redknapp, the Tottenham Hotspur manager, was recently quoted as saying of his controversial loan signing from Manchester City.
"Let's hope it continues."
So far, so good. The Togolese striker is more expressive than a screen full of emoticons, and he gave vent to the full range Sunday when he took to the field against his former club, Arsenal.
From the look of the pre-match television footage, Adebayor must have thought he was about to shoot a toothpaste commercial rather than play a football match that is routinely infused with spite.
The Arsenal back-room staff were greeted like the old friends that they probably are, even if the bitter veneer of this footballing contretemps is not supposed to allow it.
This is not one of sport's friendly rivalries. Yet on a day when the merest hint of a smug grin could have sparked the tinderbox, Adebayor was restrained.
Not that he had special reason to be otherwise, as he did not get on the score sheet himself. But there was a tangible sense that he would not have sought anything unsavoury, no matter how incendiary the provocation. Adebayor has grown up.
He is a different man to the one who ran the length of the field to goad his former fans, in celebration of a goal against Arsenal early in his Manchester City career.
He has since expressed deep regret over that incident. Those he angered back then might still need appeasing, but he is done hating.
There was an echo of that inflammatory goal celebration on 12 minutes yesterday when he went loping down Tottenham's right-wing, straight into the eye of the away support.
When the move broke down, and he was left facing the Arsenal fans at close range, his face cracked a mournful smile, the sort which said: "Sing and say what you like, I have heard it all before."
On 43 minutes he was erroneously adjudged to have committed a foul on the halfway line. He already had enough backing from the Spurs supporters to encourage him to mouth off at the referee.
His look was doubting, but he was still smiling. If invective was forthcoming, it was not coming from him.
By the next time he was spotted, Arsenal had equalised, and he had been caught offside. For the first time in the game, the tide was against him and his new team, and the good mood had apparently dissipated.
When he was thwarted shortly after, following a one-on-one chance with Arsenal's goalkeeper, he looked rueful.
Had the Arsenal resurgence continued, perhaps the Spurs striker's patience may have broken, but Kyle Walker's winning goal meant he was not tested.
After 80 minutes, when he was ruled offside as he had the goal at his mercy, the incredulous smile had returned. By the time he was substituted four minutes later, the exhausted forward could just about raise a wan effort as he trudged off.
After the full-time whistle, Adebayor was locked in what seemed to be an amiable conversation with Alex Song, the Arsenal defender. It was Song who had questioned the wisdom of his former teammate's decision to join Spurs on a season-long loan.
"Are you doing it on purpose?" Song apparently asked, insinuating that Adebayor aimed to spite the Arsenal fans by making the move.
The Togo international had reasoned that there was no malice in him jumping the divide.
"I am a professional," he has said he told Song. Judging by his demeanour yesterday, this is one professional who is happy in his work.