“Time” is the most used noun in the English language, yet it remains a mystery. We’ve just completed an amazingly intense and rewarding multidisciplinary conference on the nature of time, and my brain is swimming with ideas and new questions. Rather than trying a summary (the talks will be online soon), here’s my stab at a top ten list partly inspired by our discussions: the things everyone should know about time. [Update: all of these are things I think are true, after quite a bit of deliberation. Not everyone agrees, although of course they should.] 1. Time exists. Might as well get this common question out of the way. Of course time exists — otherwise how would we set our alarm clocks? Time organizes the universe into an ordered series of moments, and thank goodness; what a mess it would be if reality were complete different from moment to moment. The real question is whether or not time is fundamental, or perhaps emergent. We used to think that “temperature” was a basic category of nature, but now we know it emerges from the motion of atoms. When it comes to whether time is fundamental, the answer is: nobody knows. My bet is “yes,” but we’ll need to understand quantum gravity much better before we can say for sure. 2. The past and future are equally real. This isn’t completely accepted, but it should be. Intuitively we think that the “now” is real, while the past is fixed and in the books, and the future hasn’t yet occurred. But physics teaches us something remarkable: every event in the past and future is implicit in the current moment. This is hard to see in our everyday lives, since we’re nowhere close to knowing everything about the universe at any moment, nor will we ever be — but the equations don’t lie. As Einstein put it, “It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence.” 3. Everyone experiences time differently. This is true at the level of both physics and biology. Within physics, we used to have Sir Isaac Newton’s view of time, which was universal and shared by everyone. But then Einstein came along and explained that how much time elapses for a person depends on how they travel through space (especially near the speed of light) as well as the gravitational field (especially if its near a black hole). From a biological or psychological perspective, the time measured by atomic clocks isn’t as important as the time measured by our internal rhythms and the accumulation of memories. That happens differently depending on who we are and what we are experiencing; there’s a real sense in whichtime moves more quickly when we’re older. 4. You live in the past. About 80 milliseconds in the past, to be precise. Use one hand to touch your nose, and the other to touch one of your feet, at exactly the same time. You will experience them as simultaneous acts. But that’s mysterious — clearly it takes more time for the signal to travel up your nerves from your feet to your brain than from your nose. The reconciliation is simple: our conscious experience takes time to assemble, and your brain waits for all the relevant input before it experiences the “now.” Experiments have shown that the lag between things happening and us experiencing them is about 80 milliseconds. (Via conference participant David Eagleman.) 5. Your memory isn’t as good as you think. When you remember an event in the past, your brain uses a very similar technique to imagining the future. The process is less like “replaying a video” than “putting on a play from a script.” If the script is wrong for whatever reason, you can have a false memory that is just as vivid as a true one. Eyewitness testimony, it turns out, is one of the least reliable forms of evidence allowed into courtrooms. (Via conference participants Kathleen McDermott and Henry Roediger.) 6. Consciousness depends on manipulating time. Many cognitive abilities are important for consciousness, and we don’t yet have a complete picture. But it’s clear that the ability to manipulate time and possibility is a crucial feature. In contrast to aquatic life, land-based animals, whose vision-based sensory field extends for hundreds of meters, have time to contemplate a variety of actions and pick the best one. The origin of grammar allowed us to talk about such hypothetical futures with each other. Consciousness wouldn’t be possible without the ability to imagine other times. (Via conference participantMalcolm MacIver.) 7. Disorder increases as time passes. At the heart of every difference between the past and future — memory, aging, causality, free will — is the fact that the universe is evolving from order to disorder. Entropy is increasing, as we physicists say. There are more ways to be disorderly (high entropy) than orderly (low entropy), so the increase of entropy seems natural. But to explain the lower entropy of past times we need to go all the way back to the Big Bang. We still haven’t answered the hard questions: why was entropy low near the Big Bang, and how does increasing entropy account for memory and causality and all the rest? (We heard great talks by David Albert and David Wallace, among others.) 8. Complexity comes and goes. Other than creationists, most people have no trouble appreciating the difference between “orderly” (low entropy) and “complex.” Entropy increases, but complexity is ephemeral; it increases and decreases in complex ways, unsurprisingly enough. Part of the “job” of complex structures is to increase entropy, e.g. in the origin of life. But we’re far from having a complete understanding of this crucial phenomenon. (Talks by Mike Russell, Richard Lenski, Raissa D’Souza.) 9. Aging can be reversed. We all grow old, part of the general trend toward growing disorder. But it’s only the universe as a whole that must increase in entropy, not every individual piece of it. (Otherwise it would be impossible to build a refrigerator.) Reversing the arrow of time for living organisms is a technological challenge, not a physical impossibility. And we’re making progress on a few fronts: stem cells, yeast, and even (with caveats) mice and human muscle tissue. As one biologist told me: “You and I won’t live forever. But as for our grandkids, I’m not placing any bets.” 10. A lifespan is a billion heartbeats. Complex organisms die. Sad though it is in individual cases, it’s a necessary part of the bigger picture; life pushes out the old to make way for the new. Remarkably, there exist simple scaling laws relating animal metabolism to body mass. Larger animals live longer; but they also metabolize slower, as manifested in slower heart rates. These effects cancel out, so that animals from shrews to blue whales have lifespans with just about equal number of heartbeats — about one and a half billion, if you simply must be precise. In that very real sense, all animal species experience “the same amount of time.” At least, until we master #9 and become immortal. (Amazing talk by Geoffrey West.)
The Flynn effect has always been tinged with mystery. First popularized by the political scientist James Flynn, the effect refers to the widespread increase in IQ scores over time. Some measures of intelligence — such as performance on Raven’s Progressive Matrices in Des Moines and Scotland — have been increasing for at least 100 years. What’s most peculiar is how scores have increased: 1) Scores have increased the most on the problem-solving portion of intelligence tests. What’s puzzling about this increase in general intelligence is that it appears where we’d least expect it. While one might assume that IQ scores could increase over time in terms of crystallized intelligence — the part of the test that measures particular kinds of knowledge, such as being able to count or vocabulary words — it’s actually increased on measures of fluid intelligence, which is the ability to solve abstract problems. This has led some psychologists, such as Ian Dreary, to conclude that “largedifferences in scores [between generations] are demonstrated in just those situations where similaritywould be expected.” Flynn, meanwhile, marveled at the magical constancy of the effect: “It’s as if some unseen hand is propelling scores upward,” he wrote. There is, of course, no unseen hand. In recent years, many psychologists have embraced the “multiplicity hypothesis” which argues that the Flynn effect is explained by a long list of factors, such as improvements in early education (especially for girls), removal of lead paint, increased sophistication of tests, better test taking attitudes and adequate nutrition. However, despite the flurry of interest in the Flynn effect, one lingering question has remained unanswered: Does the effect apply to everyone? More specifically, does it apply to the right tail of the ability distribution, or those 5 percent of individuals who score highest on the IQ test? What makes this mystery particularly noteworthy is that many of the explanations for the Flynn effect seem particularly relevant to the left side of the bell curve, or those with below average scores. This suggests that most of the intelligence gains have come from solving low hanging fruit, fixing those glaring societal inequalities that meant millions of children lacked access to adequate food, education and medical care. Since we’ve made progress on these problems, one might suppose that the Flynn effect would start to fade, at least in developed nations. (All the low hanging fruit is gone, as Tyler Cowen might say.) Sure enough, somestudies have concluded that the Flynn effect has begun to disappear in Denmark, Norway and Britain. A brand new study, “The Flynn Effect Puzzle,” currently in press at Intelligence, and led by Jonathan Waiat Duke University, has found an interesting way to assess the right tail of the distribution. By looking at approximately 1.7 million scores of 7th grade students between 1981 and 2000 on the SAT and ACT, as well as scores of 5th and 6th grade students on the EXPLORE test, the psychologists were able to investigate the extent to which the Flynn effect exists in the right tail of the bell curve. The results were clear: The effect was found in the top 5% at a rate similar to the general distribution, providing evidence for the first time that the entire curve is likely increasing at a constant rate. The effect was also found for females as well as males, appears to still be continuing, is primarily concentrated on the mathematics subtests of the SAT, ACT, and EXPLORE, and operates similarly for both 5th and 6th as well as 7th graders in the right tail. In other words, the Flynn effect doesn’t appear to be solely caused by rising scores among the lowest quartile. Rather, it seems to be just as prevalent among the top 5 percent. The smartest are getting smarter. What might be causing this aspect of the Flynn effect? Obviously, it’s harder to explain using the low hanging fruit hypothesis, since these students (even in 1981) were probably well fed and had access to math education. This leads the scientists to focus on new forms of “environmental stimulation” as a likely explanation: Rowe and Rodgers (2002) noted that “If the rising mean were driven by the smart getting smarter, then the change might reflect the introduction of some qualitatively novel form of environmental stimulation. If the overall distribution increased in pace, the cause would lie in processes that affected everyone equally.” We find the rising mean of the entire distribution is partly driven by the smart getting smarter. This suggests some form of environmental stimulation may be at work in the right tail. The question, of course, is what this stimulation might consist of? It obviously has to be extremely widespread, since the IQ gains exist at the population level. One frequently cited factor is the increasing complexity of entertainment, which might enhance abstract problem solving skills. (As Flynn himself noted, “The very fact that children are better and better at IQ test problems logically entails that they have learned at least that kind of problem-solving skill better, and it must have been learned somewhere.”) This suggests that, because people are now forced to make sense of Lost or the Harry Potter series or World of Warcraft, they’re also better able to handle hard logic puzzles. (The effect is probably indirect, with the difficult forms of culture enhancing working memory and the allocation of attention.) As Steven Johnson argued, everything bad is good for us, especially when the bad stuff has lots of minor characters and subplots. HBO is a cognitive workout. That said, environmental stimulation remains an incomplete explanation. Even for those on the right side of the curve, intelligence gains probably have many distinct causes, from the complexity of The Wire to the social multiplier effect, which is the tendency of smart people to hang out with other smart people. (In this sense, gifted programs in schools might help drive IQ gains among the top five percent. The Internet probably helps, too.) The question, of course, is whether such factors have really changed over time. Has it gotten easier for smart people to interact with each other? Are those on the right side of the IQ distribution now more likely to have children together? Would the Flynn effect be even larger if we did more of [fill in the blank]? These questions have no easy answers, but at least we now know that they need to be answered. In the meantime, it’s wise to be modest about what we know about population changes in IQ over time; the Flynn effect remains a paradox. As Flynn himself observed, “No one knows which role IQ gains over time will eventually play.”
2) Verbal intelligence has remained relatively flat, while non-verbal scores continue to rise.
3) Performance gains have occurred across all age groups.
4) The rise in scores exists primarily on those tests with content that does not appear to be easily learned.
(Source: Wired)
