Interrupting people is way harder than it sounds.
Just ask a Boston cop.

Here’s a little story about how hard it is to get the attention of people who are thinking about something else.

In 1995, 29 year old Kenneth M. Conley, a cop in Boston, was in hot foot pursuit of a suspect. As he chased the man, he ran past a group of his colleagues who were savagely beating another suspect. It turned out that the suspect taking a beating was an undercover cop, Michael Cox – who was so displeased with his colleagues that he pressed criminal charges against them.

Conley was called as a witness at their trial. Under oath, he stated that he hadn’t seen anything. Given that Michael Cox is black, there was a suspicion that racism was involved and the jury didn’t believe Conley. He was later convicted of perjury and obstruction of justice, sentenced to nearly 3 years in jail and fined $6000.

But is it possible that Kenneth Conley was telling the truth? There is strong evidence that he may well have been.

Human beings (and other animals) seem to bring two types of attention to the world:

• The first is a narrow-focused attention to things that we already know to be important. When in this mode we can abstract the object of our attention and ignore everything else.
• The second is a much broader focus which is alert to the unexpected, the new or the incongruous.

The real kicker though, is that we appear to only be able to bring one type of attention to anything at once.

Why? It may be an energy-saving mechanism. Brains are expensive to run in terms of energy. They may only represent 2% of our body weight, but they take up around 20% of the energy we consume. Saving energy here would be an evolutionary advantage!

This effect has been demonstrated numerous times by authors like Chris Chabris (the invisible gorilla guy) who carried out an experiment based on Kenneth’s experience and discovered that around half of people didn’t see the fight.

Happily for Kenneth, he was exonerated in 2005 and awarded $647,000 in back pay – without ever going to prison. Michael Cox also remained a police officer and in 2022 was appointed as Commissioner of the Boston Police Department.

So, if we are trying to interrupt people who are doing other things, we need to try pretty hard. Predictable, familiar approaches are simply not going to cut it if we want people to see something new.