Hick’s law ( from wikipedia) describes the time it takes for a person to make a decision as a result of the possible choices he or she has.
It’s mathematically described as T = blog2(n + 1), where the simple explanation is that time T is dependent on the number of choices (n) and this relationship is logarithmic.
More choices means more time to make a decision; making it less likely any one of the provided options will be chosen. Now you know (scientifically) why landing pages for internet products has limited navigation and presents you usually only with one or two options.
When designing a poll, you should remember that you are eventually going to ask people to fill it out. A poll with more than 7 options will make things harder for the users. The rule of thumb for getting more participation is to minimize the number of options.