about the source of stress? Compared to our ancestors, there’s no
doubt that modern life does challenge us with unique attention loads,
and most of us have not figured out how to thrive under them. Levitin
writes: “The average American owns thousands of times more
possessions than the average hunter-gatherer. In a real biological
sense, we have more things to keep track of than our brains were
designed to handle.” The fact is, there’s generally not a lot we can do
about the stressor side of the equation.
And this, as Strayer explained to me, is part of our problem. “We
are products of our evolutionary environment. We create artificial
environments. Primates are good at being able to manipulate our
environment and adapt, but that’s not necessarily most consistent
with the way we think.” In other words, the world of office towers,
traffic lanes and email isn’t ideally suited to our brains’ perceptual
and cognitive systems. So what exactly are those systems? It’s
worthwhile taking a moment to lay them out, because they get to the
crux of the nature-brain connection and the best ways to salvage it.
The way Strayer sees it, moving through any environment engages
three main networks in the brain. There’s the executive network,
which includes the intellectual, task-focused prefrontal cortex and
does most of that stimulus and behavioral inhibition. There’s the
spatial network, which orients us and does what it sounds like. Then
there’s the default network, which kicks in when the executive
network flags. They are yin and yang, oil and water, working only in
opposition. You can only engage one or the other at any point in time.
The default network is our free-ranging, day-dreaming, goal-
setting, mind-wandering white noise that James so bemoaned for
luring us from the real work to be done. But it is also the charismatic,
elusive flower child of the brain. There’s much discussion these days
about whether the default network is profligate, undisciplined and
troublemaking, or the very stuff that poetry and human nature is made
of. When people are overly ruminative, depressed, self-involved and