Recently National Public Radio (NPR) ran a story entitled “Siblings Share Genes, But Rarely Personalities.” The story begins with an example of brothers who are very different, then goes on to consider research about siblings. “. . . in terms of personality, we are similar to our siblings only about 20 percent of the time. Given the fact that we share genes, homes, routines and parents, this makes no sense. What makes children in the same family so different?” The tentative answers involve several kinds of influence of family environment. For example, in the case of the two brothers with which the story begins, “When their father died, Tom was 17 and heading off to college — but Eric was only 12. So, in a sense, they grew up in different homes. Tom, the radical, grew up in a secure, two-parent home. But Eric the financial planner, as Tom points out, spent many years as the only man in a house destabilized both emotionally and financially by death.”
Browsing the Relative Index for “siblings” yields:
. . .
Siblings—family relationships 306.875
. . .
Siblings—psychological influence 155.924
Browsing the Relative Index for “families” yields:
Families—applied psychology 158.24
. . .
Families—psychological influence 155.924
Browsing the Relative Index for “personality” yields:
. . .
The interdisciplinary number for siblings is 306.875 Sibling relationships (there is even a subdivision 306.8752 Brother-brother relationship), and the interdisciplinary number for families is 306.85 Family, while the interdisciplinary number for personality is 155.2 Individual psychology. The following is relevant (from the Manual):
302–307 vs. 150 . . .
Social psychology vs. Psychology
Use 302–307 for works that focus on group behavior, including those that discuss the role of the individual in group behavior. Use 150 for works that focus on the individual, including those that discuss the influence of group behavior on the individual. If in doubt, prefer 302–307.
If we have a work that focuses on the personality of the individual, as the NPR story does, then we are looking for a subdivision of 150 Psychology. The entry 155.2 Individual psychology has the class-here note “Class here . . . character, identity, individuality, personality.” Among the subdivisions is 155.23 Traits and determinants of character and personality. A subdivision of that, 155.234 Determinants, has the class-here note “Class here environment versus heredity as determinants” and the see reference “For environmental determinants, see 155.9.” An example of a work classed in 155.234 is The Temperamental Thread: How Genes, Culture, Time and Luck Make Us Who We Are. Its LCSH include “Temperament,” “Personality—Genetic aspects,” “Personality and culture,” “Individual differences,” “Nature and nurture,” “Personality—Social aspects,” and “Personality development.”
Works that focus on environmental determinants, as the see-reference at 155.234 indicates, are classed in 155.9 Environmental psychology. Also, in the table of preference under 155 Differential and developmental psychology, 155.9 Environmental psychology is higher than 155.2 Individual psychology. Works on psychological influence of families, of siblings, are classed in 155.924 Influence of family members (built with 155.92 Influence of social environment plus 4 from 158.24 Interpersonal relations with family members). An example of a work classed in 155.924 is Born to Rebel: Birth Order, Family Dynamics, and Creative Lives. Its LCSH include “Birth order,” “Brothers and sisters,” “Individual differences,” “Personality development—Social aspects.” Another example is The Birth Order Book: Why You Are the Way You Are.
What about the Relative Index entries pointing to subdivisions of 155.4 Child psychology? They are used for works that focus on children. In the table of preference under 155 Differential and developmental psychology, 155.4–155.6 Psychology of specific ages is higher than either 155.9 Environmental psychology or 155.2 Individual psychology. Subdivisions of 155.4, however, are not used for works that cover a whole life.