The Original Nielsen Machine.

The original Nielsen rating machine was a man. Many men, in fact. They sat at home after work and on weekends with their wives and families and watched consumer consumption behavior. They discussed and probed likes and dislikes in media, products and messages. They went to the office and shared these observations in meetings, whereupon groups of professionals came up with hypotheses about behavior, preference and selling schema. These men worked at ad agencies — and when women joined the workforce in great numbers, the machine really took off.
These men and women came from many cities across the country, and periodically met at national functions so they could exchange regional views about consumer behavior and media consumption.
Over the past few decades we’ve ceded the old machine to the Nielsen audience meter and other such devices. Today we have set-top boxes and supermarket scanners to tell us if people are watching TV shows and buying our products. But the technology still has a hard time tracking when people are watching commercials, or why they are buying Crest instead of Aquafresh, so we employ anthropologists to do fieldwork. Think of them as ad nannies who tag along as part of the family.
If nannies are surrogate parents, then anthropologists are surrogate ad professionals as they were back in “the day.” The day when we were smart enough to keep our eyes and ears open and observe the behavior of consumer consumption. 

Eyes and ears still make the best ads and build the best brands.