Electronic trackers have no feelings. They are emotionally neutral, but this very fact makes them powerful mirrors of our own values and judgments. The objectivity of a machine can seem generous or merciless, tolerant or cruel. Designers of tracking systems are trying to finesse this ambivalence. A smoking-cessation program invented by Pal Kraft, a Norwegian researcher at the University of Oslo, automatically calls people who are trying to quit, asking them every day whether they’ve smoked in the last 24 hours. When the answer is yes, a recorded voice delivers an encouraging message: All is well, take it easy, try again. This mechanical empathy, barely more human than a recorded voice on the customer-service line, can hardly be expected to fool anybody. But a long line of research in human-computer interaction demonstrates that when machines are given humanlike characteristics and offer emotional reassurance, we actually do feel reassured. This is humbling. Do we really feel better when a computer pats us on the back? Yes, we do.

Jon Cousins is a 54-year-old software entrepreneur and former advertising executive who was given a diagnosis in 2007 of bipolar affective disorder. Cousins built a self-tracking system to help manage his feelings, which he called Moodscope; now used by about 1,000 others, Moodscope automatically sends e-mail with mood-tracking scores to a few select friends. “My life was changed radically,” Cousins told me recently in an e-mail message. “If I got the odd dip, my friends wanted to know why.” Sometimes, after he records a low score, a friend might simply e-mail: “?” Cousins replies, and that act alone makes him feel better. Moodscope is a blended system in which measurement is supplemented by human sympathy. Self-tracking can sometimes appear narcissistic, but it also allows people to connect with one another in new ways. We leave traces of ourselves with our numbers, like insects putting down a trail of pheromones, and in times of crisis, these signals can lead us to others who share our concerns and care enough to help.

Often, pioneering trackers struggle with feelings of being both aided and tormented by the very systems they have built. I know what this is like. I used to track my work hours, and it was a miserable process. With my spreadsheet, I inadvertently transformed myself into the mean-spirited, small-minded boss I imagined I was escaping through self-employment. Taking advantage of the explosion of self-tracking services available on the Web, I started analyzing my workday at a finer level. Every time I moved to a new activity — picked up the phone, opened a Web browser, answered e-mail — I made a couple of clicks with my mouse, which recorded the change. After a few weeks I looked at the data and marveled. My day was a patchwork of distraction, interspersed with valuable, but too rare, periods of focus. In total, the amount of uninterrupted close attention I was able to muster in a given workday was less than three hours. After I got over the humiliation, I came to see how valuable this knowledge was. The efficiency lesson was that I could gain significant benefit by extending my day at my desk by only a few minutes, as long as these minutes were well spent. But a greater lesson was that by tracking hours at my desk I was making an unnecessary concession to a worthless stereotype. Does anybody really believe that long hours at a desk are a vocational ideal? I got nothing from my tracking system until I used it as a source of critical perspective, not on my performance but on my assumptions about what was important to track.

People are not assembly lines. We cannot be tuned to a known standard, because a universal standard for human experience does not exist. Bo Adler, a young computer scientist at Fujitsu Laboratories of America, is one of the most committed self-trackers I’ve ever met: during his most active phase he wore a blood-pressure cuff, pulse oximeter and accelerometer all day long, along with a computer on a harness to collect the data. Adler has sleep apnea, and he is trying to figure it out. When he became too self-conscious going to the gym in his gear, he wore a Google T-shirt to throw people off. Maybe he was a freak, but at least people could mistake him for a millionaire freak.

“Here’s what they told me was the normal surgical course of treatment,” Adler explained. “First they were going to cut out my tonsils, and if that didn’t work, they would break my jaw and reset it to reposition my tongue, and finally they would cut out the roof of my mouth. I had one question: What if my case is different? They said, ‘Let’s try the standard course of treatment first, and if that doesn’t work, then we’ll know your case is different.’ ” Adler recognized what this proposal meant: it meant that his doctors had no cure for different. They wanted to see him as a standard case, because they have treatments for the standard cases. Before Adler underwent surgery, he wanted some evidence that he was a standard case. Some of us aren’t standard, after all; perhaps many of us aren’t.

Adler’s idea that we can — and should — defend ourselves against the imposed generalities of official knowledge is typical of pioneering self-trackers, and it shows how closely the dream of a quantified self resembles therapeutic ideas of self-actualization, even as its methods are startlingly different. Trackers focused on their health want to ensure that their medical practitioners don’t miss the particulars of their condition; trackers who record their mental states are often trying to find their own way to personal fulfillment amid the seductions of marketing and the errors of common opinion; fitness trackers are trying to tune their training regimes to their own body types and competitive goals, but they are also looking to understand their strengths and weaknesses, to uncover potential they didn’t know they had. Self-tracking, in this way, is not really a tool of optimization but of discovery, and if tracking regimes that we would once have thought bizarre are becoming normal, one of the most interesting effects may be to make us re-evaluate what “normal” means.

“My girlfriend thinks I’m the weird person when I wear all these devices,” Bo Adler says. “She sees me as an oddity, but I say no, soon everybody is going to be doing this, and you won’t even notice.”