Some new research (from a company that makes tea) has found that tea has a chemical that helps people be more attentive.
“Every cup of tea naturally contains the amino acid theanine. Tea is virtually the only dietary source of theanine, apart from the edible bay boletes mushroom, which explains why sometimes only tea will do.
The effects of 50mg theanine – the amount present in 2-3 cups of PG tips tea is known* to stimulate alpha brain waves which are associated with being relaxed yet alert. Alpha activity is thought to be important for the ability to focus attention.”