REDMOND, Washington (Reuters) - As Microsoft CEOs past and present gathered here to celebrate the company's 50th birthday, one leader said he is targeting a particular metric's improvement to guide his strategy on artificial intelligence.

Mustafa Suleyman, chief executive of Microsoft AI, said his consumer and research division is tracking the usual measures of adoption for the company's AI assistant called Copilot. These include daily and weekly active users, distribution, and usage intensity for Copilot's consumer offering, he said.

But Suleyman's interest lies elsewhere.

"I really, really focus the team on SSR, the rate of successful sessions," he said in an interview.

In an older era when consumers gave less real-time feedback on software, the time they spent with a product -- on social media, for instance -- or the problems they could solve represented crude "proxies for quality," he said.

"Now, we actually get to learn from the anonymized logs and extract the sentiment," said Suleyman, who joined Microsoft ( MSFT ) about a year ago after leading the startup Inflection AI. Suleyman was one of the only Microsoft ( MSFT ) executives other than former CEOs Bill Gates and Steve Ballmer and current CEO Satya Nadella to speak on stage at Microsoft's ( MSFT ) Friday event at its Redmond, Washington, headquarters.

Suleyman said Microsoft ( MSFT ) has tasked an AI model itself to assess such sentiment and help determine Copilot chats' SSR.

"Over the last four months, it's gone up dramatically, and that's what we optimize for," he said.

Suleyman declined to state the rate in absolute terms or disclose other Copilot metrics.

The company last fall announced a more amiable voice for its consumer Copilot and the ability to analyze web pages for users as they browse.

On Friday, Microsoft ( MSFT ) demonstrated further features for Copilot: personalized podcasts, a tool to help consumers research complex queries, and eventually a look for Copilot that can be custom to each user and conversation.

"I would definitely go for something that was cutesy," said Suleyman, "like a little Furby-type thing."

(Reporting by Jeffrey Dastin; Editing by Leslie Adler)