Most of us know someone who seems to be perennially pessimistic about things—a spouse, co-worker or friend. And it’s also true that most of us have an acquaintance or two who is rarely discouraged by anything that comes along. To an observer it looks as if they are on two ends of a continuum, and in some ways that is accurate.

From those who do research into this kind of thing, we’ve learned that such dispositional differences are influenced profoundly by heredity, some say as much 50-80%! Whether on the positive end of the continuum or the negative end (or more likely near the middle), each of us seem to have a dispositional range where we operate. As individuals, we’ve had the experience of trying hard to appear happier and more optimistic (or maybe even more pessimistic) than we really feel, just to get through a situation or event. Or we are up or down for a period of time depending on circumstances. It changes for a little while, but over the long term, we all have a dispositional style that we generally return to. In other words, those with a half-empty perspective can work toward the middle, but they’re probably never going to see the world in the same way as those born with more rose-colored glasses. And those who are higher in optimism may drift lower, but are never going to become a Chicken Little (The sky is falling! The sky is falling!).

One of psychology’s excellent researchers has written a book that gives us a little different perspective on this, suggesting that some of this difference we see is due to strategies to manage anxiety. Julie Norem, author of “The Positive Power of Negative Thinking,” calls these strategic optimism and defensive pessimism, and they both seem to be adaptive.  I use this book in my classes and recommend it to patients who live or work with a person whose first response is to see things in the opposite way from their own.

To illustrate this, just imagine that your neighborhood is planning a huge garage sale and everyone from all around the cul de sac will contribute items, and then when it’s over, everyone will join together for an enormous potluck and barbecue.  Sounds great, doesn’t it? And if everyone on the street is a positive, glass-is-half-full kind of person (or is using strategic optimism), they’ll jump in there and start taking stuff out onto the corner and putting up signs with great enthusiasm.  It’s only the half-empty person (or those using defensive pessimism) who will say, “Wait a minute, don’t you think we should put an ad in the paper? Don’t you think we should figure out a good date for this when everyone will be here? Do you think we should be doing this on a holiday? What will we do if it rains? Do you have a tarp? Can we get things inside garages? Who will handle the money?” And on, and on.

We all like to be around positive, happy, enthusiastic people, with the energy and willingness to enjoy putting an idea into action. We enjoy this so much, in part, because someone in a group usually has a bit of that “negative thinking” that brings out the strategies we’ll use if something goes wrong. We don’t like to hear about all that might go wrong when we’re in that enthusiastic mood of making things happen, but as our plans are running off the rails, we are delighted to have a back-up position ready. That person who uses defensive pessimism is often seem as annoying, and the person using strategic optimism is seen as too unrealistic, however, viewing these as different strategies could lead people to compliment each other more in marriage and at work.

In general, though, it seems that—if nudges are needed in disposition—they are generally needed toward greater optimism (though extreme optimism has its downside). With that in mind, I recommend a second resource: Martin Seligman’s book, Learned Optimism. And, for the parents of young children, Seligman’s The Optimistic Child. Both are worth looking into for the scientific basis of our placement on that half-full-or-half-empty continuum, and are essential for improving optimism, certainly if you have a tendency toward depression rather than mere pessimism.