It does not even matter of the smartphone is off, your brain stops working in the presence of the shiny toy.
The study was prepared by the McCombs School of Business at The University of Texas at Austin.
McCombs Assistant Professor Adrian Ward and co-authors conducted experiments with nearly 800 smartphone users in an attempt to measure, for the first time, how well people can complete tasks when they have their smartphones nearby even when they're not using them.
In one experiment, the researchers asked study participants to sit at a computer and take a series of tests that required full concentration to score well. The tests measured participants' available cognitive capacity - that is, the brain's ability to hold and process data at any given time.
Before beginning, participants were randomly instructed to place their smartphones either on the desk face down, in their pocket or personal bag, or in another room.
All participants were instructed to turn their phones to silent. The researchers found that participants with their phones in another room significantly outperformed those with their phones on the desk, and they also slightly outperformed those participants who had kept their phones in a pocket or bag.
We are not sure about this as it did not identify the brands of the smartphone. iPhone users have a low cognitive ability to start with, otherwise they would not think shelling out $650 for a $300 phone was a good idea.