Gullibility

Name(s): 
Credulity
Naïvety
Unsophistication
Nature

Gullibility is a failure of social intelligence in which a person is easily tricked or manipulated into an ill-advised course of action. It is closely related to credulity, which is the tendency to believe unlikely propositions that are unsupported by evidence.

Classes of people especially vulnerable to exploitation due to gullibility include children, the elderly, and the developmentally disabled.

Source: Wikipedia

Type 
(F) Fuzzy exceptional problems