From chapter 14 on pages 572 and 573, a topic that was of great interest to me was graphology, the study and analysis of writing tied with psychology. Graphology claims that many personality characteristics of an individual can be found in their handwriting and has many notable figures as examples. Everyone from presidential candidates to numerous celebrities have been the subject of these studies, but it turns out to have a lot of flaws in its ideology.
An example of flaws found in this theory can be seen in its biggest application. Graphology was/is often used by employers to try and predict the success of potential employees while also weeding out those that, according to their handwriting may possess undesirable traits for the work place. The problem is that the handwriting analyzed also happened to be from a handwritten explanation on their previous experience. This content of the paragraphs analyzed confounds the correlation, making it invalid. Another problem with this theory is that it relies mainly on heuristics, especially the representative heuristic. This means it generalizes conclusions about people based off of similar writing styles, therefore resulting in inaccurate results.
These inaccurate results may have caused a lot of misjudgments in the workplace or in many other applications such as historical analyses of philosophers in the past. While we can't rely on graphology it is a fascinating concept and there is plenty of literature that claims to have picked apart many prominent individuals' handwriting in a way that is almost hard not to believe.