Since our minds are smaller than the world, the world tends to be more complicated than our mental models of it. Yes, sometimes we think things are more complex than they really are, but far more often reality is more complex than we appreciate. All else equal, since far mode makes us neglect detail, it tends to make us think things are even simpler, thus increasing our error. So far mode is a major source of human overconfidence. From the latest JPSP:

People generally tend to believe they are more competent than they actually are, and this effect is particularly pronounced among poor performers. … One striking demonstration, the illusion of explanatory depth (IOED), arises when people overestimate their ability to explain mechanical and natural processes. For example, people know that a zipper closes because it has teeth that somehow interlock, but they know very little about how the teeth actually interlock to enable the bridging mechanism. Similarly, many people know vaguely that an earthquake occurs because two geological plates collide and move relative to one another, but again they know little about the mechanism that initially produces these collisions. Nonetheless, people believe they understand these concepts quite deeply and are surprised by the shallowness of their own explanations when prompted to describe the concepts thoroughly. …

People who construe a ballpoint pen abstractly are more likely to focus on the pen’s function and perhaps its global appearance. In contrast, people who construe the pen concretely are more likely to focus on how well they understand how its parts work together to enable the pen to function—in this case, the appropriate metacognition. Accordingly, people are less likely to overestimate their understanding of how the pen works when their introspections focus appropriately on the pen’s concrete features rather than its abstract features. …

In six studies, we showed that IOEDs arise at least in part because people sometimes adopt an inappropriately broad or abstract construal style when evaluating their understanding of concrete processes. … Participants … experienced larger IOEDs the more abstractly they construed 13 basic human behaviors. … Participants rated their knowledge of how three mechanical devices worked more accurately when the devices were framed more narrowly according to their component parts. When asked to express how those devices worked, only participants in the broad construal condition were surprised by the incompleteness of their explanations. …

Participants were induced to adopt a concrete or an abstract mindset by expressing how (concrete) or why (abstract) they engage in certain everyday processes, like getting dressed in the morning. Again, participants in an abstract mindset tended to show a significantly greater IOED. … Participants … reported understanding their favored 2008 Presidential candidate’s policies better than they actually did when asked to express those policies in writing. … Participants who adopted a more abstract construal style showed a more pronounced illusion of political sophistication. …

Our findings suggest that … when adopting an abstract construal style, people might therefore be systematically overconfident about what the future holds and how well they understand themselves and others. … The IOED is both similar to and distinct from a range of overconfidence biases documented. … According to one account, egocentric over-confidence effects tend to emerge because people anchor on their own subjective experiences and fail to adequately account for the experiences and abilities of other people. … Other researchers have suggested that people are overconfident because … their memories tend to be overpopulated with successes rather than failures.