Jumping to conclusions

Jumping to conclusions (also rushing to conclusions) is defined by thefreeditionary.com as "to judge or decide something without having all the facts; to reach unwarranted conclusions".^[1]^[2] Because it involves making decisions without having enough information to be sure you're right, this can result in badly made or rash decisions. This action is be assosiated with impulsiveness and can be a good or bad trait.

Three specific subtypes are^[3]^[4]:

Mind reading – Sense of access to special knowledge of the intentions or thoughts of others.
Fortune telling – Inflexible expectations for how things will turn out before they happen.
Labeling - Overgeneralizations done because of labelling all the members of a group with the characteristics seen in some, i.e, it involves using an unfavourable term to describe a complex person or event.

References

^ http://www.englishclub.com/ref/esl/Idioms/J/jump_to_conclusions_434.htm
^ http://idioms.thefreedictionary.com/jump+to+conclusions
^ http://panicdisorder.about.com/b/2011/09/22/dont-jump-to-conclusions.htm
^ http://daphne.palomar.edu/jtagg/jump.htm