American actor Scarlett Johansson says she was "shocked" and "angered" to find OpenAI had given its ChatGPT chatbot a voice “eerily similar” to her own, after she previously declined to lend her likeness to the popular AI platform.

Johansson says OpenAI only “reluctantly agreed” to pause the voice, known as Sky, after she called in lawyers.

In a statement posted on Monday, OpenAI said it was “working to pause” Sky, which was one of five voices users could interact with using ChatGPT's voice mode.

Johansson, who famously lent her voice to a fictional AI assistant named Samantha in the 2013 film Her, said in a statement to US media on Tuesday that OpenAI CEO Sam Altman had contacted her in September 2023 to ask if she would like to provide her voice for ChatGPT.

Johansson said she declined the offer “after much consideration and for personal reasons”.

She claimed Altman then contacted her agent two days before OpenAI revealed its GPT-4o model earlier this month, and asked her to reconsider.

“Before we could connect, the system was out there,” she said.

“When I heard the released demo, I was shocked, angered and in disbelief that Mr Altman would pursue a voice that sounded so eerily similar to mine that my closest friends and news outlets could not tell the difference.”

Sky has been available as a ChatGPT voice since September 2023, when OpenAI first launched ChatGPT’s voice mode.

But the voice is more expressive and has a greater ability to judge emotions in GPT-4o, leading to more comparisons to Johansson and even a joke about the similarities on Saturday Night Live.

On the day of OpenAI’s GPT-4o announcement, Altman posted the word “her” on social media platform X.

Altman denies claim Johansson’s voice was copied

Johansson said her lawyers had written two letters to OpenAI, asking the company to explain how the Sky voice was created.

In its statement, OpenAI says the voice of Sky “is not an imitation of Scarlett Johansson but belongs to a different professional actress using her own natural speaking voice”.

It said it could not name the actor, due to privacy concerns.

“We believe that AI voices should not deliberately mimic a celebrity's distinctive voice,” the company said.

In a statement to The Associated Press, Altman said OpenAI had cast the voice actor behind Sky “before any outreach” to Johansson.

“The voice of Sky is not Scarlett Johansson’s, and it was never intended to resemble hers,” Altman said.

“Out of respect for Ms. Johansson, we have paused using Sky’s voice in our products. We are sorry to Ms. Johanssons that we didn’t communicate better.”

OpenAI said it chose the five voices of ChatGPT after receiving more than 400 submissions from voice and screen actors.

“We support the creative community and worked closely with the voice acting industry to ensure we took the right steps to cast ChatGPT’s voices,” it said.

“Each actor receives compensation above top-of-market rates, and this will continue for as long as their voices are used in our products.”

In her statement, Johansson said OpenAI had questions to answer “in a time when we are all grappling with deepfakes and the protection of our own likeness, our own work, our own identities".

“I look forward to resolution in the form of transparency and the passage of appropriate legislation to help ensure that individual rights are protected,” she said.

OpenAI has faced multiple lawsuits from media companies and authors, who claim the company trained its systems by using their intellectual property without permission.