Positive findings from research studies can also result from such psychological mechanisms, or as a result of experimenter bias, methodological flaws such as lack of blinding, or publication bias; positive reviews of the scientific literature may show selection bias, in that they omit key studies that do not agree with the author's position.
Positive findings from research studies can be influenced by psychological factors, experimenter bias, flawed methodologies (like a lack of blinding), and publication bias.  Reviews of the scientific literature might also exhibit selection bias, excluding studies that contradict the reviewer's viewpoint.