Boundaries of the mind refers to a personality trait concerning the degree of separateness ("thickness") or connection ("thinness") between mental functions and processes. Thin boundaries are associated with open-mindedness, sensitivity, vulnerability, creativity, and artistic ability. People with thin boundaries may tend to confuse fantasy and reality and tend to have a fluid sense of identity, so that they tend to merge or lose themselves in their relations with others. People with thick boundaries differentiate clearly between reality and fantasy and between self and other, and tend to prefer well-defined social structures. The concept was developed by psychoanalyst Dr. Ernest Hartmann from his observations of the personality characteristics of frequent nightmare sufferers. The construct has been particularly studied in relation to dream recall and lucid dreaming.
Dr. Ernest Hartmann observed that people who suffer frequent nightmares had distinctive personality characteristics he described as "unguarded", "undefended", "vulnerable", "artistic", and "open". People with these characteristics seem unable to screen out frightening images and feelings originating in their dreams. They also lack barriers between their own identity and those of others, or between their own beliefs and unconventional ideas. Hartmann proposed that such people have "thin" boundaries between their mental processes and argued that thinness or thickness of boundaries was "a broad dimension of personality and an aspect of the overall organization of the mind." He considered the concept to be similar to William James' concept of "tender-mindedness" and to Blatt and Ritzler's "permeable ego boundaries". The construct is measured with the Boundary Questionnaire which assesses thinness of boundaries in relation to a variety of areas, including boundaries between sleeping and waking, thoughts and feelings, and persons, places, and values. People with thick boundaries tend to see the world in "black-and-white" terms, whereas those with thin boundaries tend to be more aware of "shades of gray". Women tend to have thinner boundaries than men, and boundaries tend to become thicker with age.
The Boundary Questionnaire consists of 145 five-point scales covering the following 12 areas:
Additionally, a total score (SumBound) reflecting boundary thinness was derived by summing the ratings of 138 items.
The Boundary Questionnaire has been related to the Five Factor Model of personality, and "thin boundaries" are mostly associated with openness to experience, particularly the facets of openness to fantasy, aesthetics, and feelings, although some of the content was correlated with neuroticism, extraversion, and low conscientiousness. Scores on the questionnaire are also positively correlated with absorption, transliminality, hypnotisability, and suggestibility. Thin boundaries are also associated with the Feeling and Intuition scales of the Myers-Briggs Type Indicator.
Persons diagnosed with schizotypal personality disorder or with borderline personality disorder tend to have thinner boundaries than the rest of the population, whereas people with obsessive-compulsive disorder tend to have thicker boundaries. On the MMPI thin boundaries are associated with high scores on the paranoia scale, and in males with high femininity and low defensiveness. Thin boundaries in males are therefore associated with willingness to accept "feminine" aspects of the self, whereas men with thick boundaries believe that "men are men, women are women".
Research has found that people with thin boundaries have more frequent dream recall, have more nightmares, and may also have longer, more intense dreams, with more bizarre content. Additionally, people with thin boundaries tend to value their dreams more, especially their meaningfulness and creative aspects. People with thin boundaries are more likely to report having had childhood nightmares, suggesting that boundary thinness may be relatively stable across the lifespan.
Adherence to new age beliefs and practices, such as yoga, reiki, divination, and astrology, is positively correlated with thin boundaries as well as with measures of schizotypy and magical thinking. New age beliefs and thin boundaries may be related through such shared factors as a sense of "connectedness", holism and emotional sensitivity, as well as a thinking style defined by looseness of association. That is, new age beliefs and practices encourage the development of emotional sensitivity and a sense of "holistic self-awareness" associated with the belief that "everything is connected."