People will do just about anything while watching television — except watch commercials, according to a study by the London Business School.

"In most cases when the commercial break began...households decided to do something else," says Mark Ritson, a professor of marketing at the school.

The study found people took in between 23 and 55 per cent of ads while watching television.

The school says TV advertising is worth $2.8 billion a year.

Ritson filmed the t.v. rooms of eight households. He says in one example, a 31-year-old man timed his dinner around the ad breaks.

"He knew when the break was to put his pasta on, and when to put his sauce on," says Ritson.

Ritson says the study discovered six ad-break behaviours:

• tasking: doing chores
• social interaction between couples (talking, hugging, kissing)
• reading
• channel-surfing
• watching ads
• interacting with ads (e.g. singing the jingles)

Ritson says his research disproves a key assumption about the effect of TV on people's viewing habits.

"Ask not what the advertisements do to people, ask what people do to advertisements."

The study also shows larger groups of people are more likely to ignore advertising because of the "friends effect" — a group of people prefers talking to each other.

As well, more people pay attention to ads later at night, after prime-time.

Ritson says the "peoplemeters" — which produce TV ratings — only indicate how many people are present when a TV is on, not whether people are actually watching.