"Blue Mondays" Aren't Really Blue - So Why Do We Think They Are? DESPITE the beating that Mondays have taken in pop songs - Fats Domino crooned "Blue Monday, how I hate blue Monday" - the day does not deserve its gloomy reputation. Two colleagues and I recently published an analysis of a remarkable yearlong survey by the Gallup Organization, which conducted 1,000 live interviews a day, asking people across the United States to recall their mood in the prior day. We scoured the data for evidence that Monday was bluer than Tuesday or Wednesday. We couldn't find any. Mood was evaluated with several adjectives measuring positive or negative feelings. Spanish-only speakers were queried in Spanish. Interviewers spoke to people in every state on cellphones and land lines. The data unequivocally showed that Mondays are as pleasant to Americans as the three days that follow, and only a trifle less joyful than Fridays. Perhaps no surprise, people generally felt good on the weekend - though for retirees, the distinction between weekend and weekdays was only modest. Likewise, day-of-the-week mood was gender-blind. Over all, women assessed their daily moods more negatively than men did, but relative changes from day to day were similar for both sexes. And yet still, the belief in blue Mondays persists. Several years ago, in another study, I examined expectations about mood and day of the week: two-thirds of the sample nominated Monday as the "worst" day of the week. Other research has confirmed that this sentiment is widespread, despite the fact that, well, we don't really feel any gloomier on that day. The question is, why? Why do we believe something that our own immediate experience indicates simply isn't true? As it turns out, the blue Monday mystery highlights a phenomenon familiar to behavioral scientists: that beliefs or judgments about experience can be at odds with actual experience. Indeed, the disconnection between beliefs and experience is common. Vacations, for example, are viewed more pleasantly after they are over compared with how they were experienced at the time. And motorists who drive fancy cars report having more fun driving than those who own more modest vehicles, though in-car monitoring shows this isn't the case. The same is often true in reverse as well: we remember pain or symptoms of illness at higher levels than real-time experience suggests, in part because we ignore symptom-free periods in between our aches and pains. HOW do we make sense of these findings? The human brain has vast, but limited, capacities to store, retrieve and process information. Yet we are often confronted with questions that challenge these capacities. And this is often when the disconnect between belief and experience occurs. When information isn't available for answering a question - say, when it did not make it into our memories in the first place - we use whatever information is available, even if it isn't particularly relevant to the question at hand. When asked about pain for the last week, most people cannot completely remember all of its ups and downs over seven days. However, we are likely to remember it at its worst and may use that as a way of summarizing pain for the entire week. When asked about our current satisfaction with life, we may focus on the first things that come to mind - a recent spat with a spouse or maybe a compliment from the boss at work. Several mental processes like these have been identified and are called cognitive heuristics. The so-called peak-end heuristic is particularly well researched and is the tendency to emphasize peaks and recent experience when one summarizes over a period of time. In the case of the blue Monday belief, it is likely that heuristics are at work. Thinking that Monday is the worst day of the week may be based on our innate attention to change: the shift from pleasant Sundays to ordinary Mondays constitutes the largest change in mood over a week for a person working a typical weekday shift. So, when thinking about mood on different days of the week, we react to change rather than the absolute levels of daily mood - a so-called contrast effect. In doing so we get it wrong, at least in terms of representing the actual mood experience in memory. That we can so readily distort what happened in the past has far-ranging implications. Decision-making often draws on knowledge from our experiences, yet given that the memories of these can be flawed, so may be the decisions. And there is evidence that this happens. Memories of an uncomfortable medical test, like a colonoscopy, influence whether or not such procedures are repeated in a timely manner. In the same way, faulty memory can hamper the development of pain medications. A new drug may in fact be effective in reducing daily pain levels, yet if the evaluation of the treatment is based on retrospective measures, this effect could go undetected as memories of pain-free moments are subsumed by memories of pain. So although debunking blue Mondays provides a clearer view of daily life experience, the real value of this work comes from understanding the psychological processes that create our memories - and the impact this has on our decisions. Arthur A. Stone is a professor of psychiatry and behavioral science at Stony Brook University and a senior scientist at the Gallup Organization.