Denser cities does not equal to productivity

I was recently reading an article talking about higher productivity in denser cities. However, I felt that the article had a misleading header. It's not density that leads to productivity. It's interaction.

You can be in a dense city but if people do not talk to one another, do not listen to each other, do not interact with one another, it does not matter how dense it is. The key to higher productivity is interaction. There is a need to create this kind of interactive environment to improve productivity. It has nothing to do with denser cities.

Seriously, I will say those who say denser cities lead to improve productivity is taking the easy way out. It's way much easier to make cities denser, but way more difficult to improve interaction between people. It's like trying to sell to people you have to work less to be more productivity due to the way humans are structured. Oh well.