The internet has spawned subtle forms of influence that can flip elections and manipulate everything we say, think and do ... Most of us have heard of at least one of these methods: subliminal stimulation, or what Packard called ‘subthreshold effects’ – the presentation of short messages that tell us what to do but that are flashed so briefly we aren’t aware we have seen them. In 1958, propelled by public concern about a theatre in New Jersey that had supposedly hidden messages in a movie to increase ice cream sales, the National Association of Broadcasters – the association that set standards for US television – amended its code to prohibit the use of subliminal messages in broadcasting. ... Subliminal stimulation is probably still in wide use in the US – it’s hard to detect, after all, and no one is keeping track of it – but it’s probably not worth worrying about. ... what would happen if new sources of control began to emerge that had little or no competition? And what if new means of control were developed that were far more powerful – and far more invisible – than any that have existed in the past? And what if new types of control allowed a handful of people to exert enormous influence not just over the citizens of the US but over most of the people on Earth? ... It might surprise you to hear this, but these things have already happened. ... The shift we had produced, which we called the Search Engine Manipulation Effect (or SEME, pronounced ‘seem’), appeared to be one of the largest behavioural effects ever discovered.