Twitter search query problems with the OR clause



I am trying to execute queries using this address:
I have a list of tags (each being one or more words) to search by, grouped by an OR clause.

Strangely, sometimes removing one or more of these tags from the query results in more tweets being returned. Logically, it shouldn’t be so, should it?


?lang=it&q=intervista OR heike has the giggles returns 1 result having to do with second tag
?lang=it&q=heike has the giggles OR intervista same as above
?lang=it&q=heike has the giggles returns same result as above
?lang=it&q=intervista returns lots of results

Am I doing something wrong with the query?



A search of “a OR b c” means “(a OR b) and c”.

On the other hand, “a OR (b c)” is more what you want.


Thank you very much