If the human subjects were Stanford students 30 years ago, they were pretty much my age cohort and most probably also had similar technologically-rich US middle class experiences in childhood.

Most in this cohort grew up with many kinds of electronic device. This includes kid-focused, hand-held games like a "speak and spell" or a "simon says" game and other toys that played recorded voices. Video game arcades and home video games were common and games were full of sequential prompting and story telling. But I think we saw these as conduits for content, not defaulting to any belief that there was agency in the device.

There were also portable radios and tape players, so we were used to technology delivering social content. Also, there were plenty of digital controls on home appliances as mentioned previously. Microwave ovens, washing machines, CD players, programmable VCRs, programmed irrigation timers, etc. These were all things that had some level of automated and asynchronous behavior.

I remember one of my older relatives back in the 1980s liked to jokingly quote a theory about "the perversity of inanimate objects" that he had picked up as a technician in the US Navy. And yet we would have raised an eyebrow if anybody really responded to devices as social actors. It would be as strange as if someone talked to plants or to their shoes.