Can you determine personality from handwriting?
The short answer is ‘no’.
It is important to understand that this type of claim, being able to assess personality from a person’s writing, falls completely outside the scope of forensic document examination. In North America, someone who claims to be able to determine personality traits based upon handwriting is generally called a ‘graphologist’, and their field is called ‘graphology’.
The distinction maybe confusing for those who might interpret the word ‘graphologist’ in the broader sense of ‘someone who studies handwriting’; however, that is not how the term is used in the modern forensic science domain. In general, the broader community of Forensic Document Examiners do not consider themselves to be graphologists because they examine handwriting solely to assess questions relating to authorship (as well as performing analyses relating to other aspects of document production). They are trained to do such tasks based upon the study of habitual motor patterns, biomechanics, and neuro-physiology; all aspects of handwriting that have little or nothing to do with the ‘personality traits’ of the writer. At the same time, graphologists do not generally receive any training that would qualify them to do authorship assessments.
Since ‘graphology’ is not my area of expertise I won’t any comment further on the validity of any claims regarding handwriting and personality assessment. Instead, I recommend a couple of independent resources: first, a BC Civil Liberties’ article, The use of graphology as a tool for employee hiring and evaluation and, second, Quackwatch’s How Graphology Fools People article, both of which provide a good analysis. Draw your own conclusions.
So, as I indicated at the start of this answer, this is a clear and definite “no — I cannot determine personality from handwriting”.