Page 48 - Mind Games The Aging Brain and How to Keep it Healthy

32 • Chapter 2

write with the hand in a noninverted position. One percent
of the right-handed population and 44 percent of the left-
handed population write with the hand in an inverted posi-
tion (see Figure 2-6). Dr. Jerre Levy performed experiments
that revealed that the inverted hand position is a biological
marker indicating that the hemisphere considered dominant
for analytical specialization is on the same side as the writ-
ing hand. For those people who write with the hand in a
noninverted position, the hemisphere opposite that hand is
dominant. For discussion purposes, and because it is the
case for most of the population, we will consider the left
hemisphere of the brain to be the site for verbal and analyt-
ical abilities for the rest of this text.
We have all heard jokes regarding the differences be-
tween men and women. There is a biological basis for many
of the qualities men and women find confusing about each
other. For example, men and women differ at a very basic
level from the description just given for the dominant hemi-
sphere. While men’s verbal abilities are predominantly

Noninverted

Inverted

Figure 2-6 Hand position as a marker for hemisphere dominance