Decision Science News

NOT SURE WHY DAYLIGHT SAVINGS TIME IS WHEN IT IS

Last week we posted a nice theory about daylight savings time, in particular, that its dates were chosen to reduce variance in the time of sunrise. It looked plausible from the graph.

We were talking to our Microsoft Research colleague Jake Hofman who suggested “why don’t you just find the optimal dates to change the clock by one hour?” So we did. We got the times of sunrise for New York City from here, threw them into R, and optimized.

The result was surprising. The dates of daylight savings time do not come close to minimizing variance in sunrise. If they did, in 2012, DSL would have started on March 25th and ended on September 28th. In actuality, it started on March 11th and ended on November 4th. For NYC, daylight savings time starts too early and ends too late to minimize variance in sunrise. In the heatmap above, the higher the variance, the bluer the squares. The variance minimizing dates are shown in black, and the actual ones in red. The same color coding is used in the plot below, which also shows how the hours would shift if the variance minimizing dates were chosen (see last week’s post for how they actually change).

So what then is the logic behind DSL? We’re not quite sure. There are some leads in this article. We also learned that the US lengthened DSL in 2007 as it believes it that DSL saves energy, but it is not clear that it does.

If you want to play with this, the data are here: Sunrise and Sunset data for New York City in 2012. The source of the data is here.


library(ggplot2)
#data from http://aa.usno.navy.mil/data/docs/RS_OneYear.php
setwd("C:/Dropbox/Projects/Sunrise/")
df=read.table("nyc_sunrise.txt",colClasses="character")
temp_times=unlist(df[,c(paste("V",seq(2,24,2),sep=""),
paste("V",seq(3,25,2),sep=""))])
l=length(temp_times)/2
df=data.frame(day=1:31,stime=temp_times,
sun=c(rep("rise",l),rep("set",l)))
rm(temp_times,l)
hour=as.numeric(substr(df$stime,1,2))
minute=as.numeric(substr(df$stime,3,4))/60
df$time=hour+minute
df=subset(df,!is.na(df$time))
df$day_of_year=1:(nrow(df)/2)
p=ggplot(data=subset(df,sun=="rise"),aes(x=day_of_year,y=time))
p=p+geom_line()
p=p+geom_line(data=subset(df,sun=="set"),aes(x=day_of_year,y=time))
p
zerovec=function(i,j){
c(rep(0,i-1),
rep(1,j-i+1),
rep(0,len-j))}
currvec=df[df$sun=="rise","time"]
len=length(currvec)
get_var=function(i,j) {
var(currvec +
zerovec(i,j))}
vget_var=Vectorize(get_var)
result=expand.grid(spring_forward=45:125,fall_back=232:312)
result=subset(result,spring_forward<fall_back)
result$var=with(result,vget_var(spring_forward,fall_back))
resout=result[which.min(result$var),]
resout
#Heatmap
p =ggplot(data=result, aes(spring_forward, fall_back)) +
geom_tile(aes(fill = var), colour = "white") +
scale_fill_gradient(low = "white", high = "steelblue")
p=p+geom_vline(xintercept=as.numeric(resout[1]))+
geom_hline(yintercept=as.numeric(resout[2]))
p=p+geom_vline(xintercept=71,color="red")+
geom_hline(yintercept=309,color="red")
p=p+ylab("Fall Back Day of Year\n")+theme_bw()
p=p+xlab("\nLeap Forward Day of Year")+opts(legend.position="none")
p
ggsave("heatmap.pdf",p,width=6)
#For 2012, optimal spring forward day (85)is 03/25/2012
#For 2012, optimal fall back day (272) is 09/28/2012
#Actual DSL start was 3/11/2012 (71)
#Actual DSL end was 11/4/2012 (309)
p=ggplot(data=subset(df,sun=="rise"),
aes(x=day_of_year,y=time+zerovec(85,272)))
p=p+geom_line()
p=p+geom_line(data=subset(df,sun=="set"),
aes(x=day_of_year,y=time+zerovec(85,272)))
p=p+geom_vline(xintercept=85,lwd=2)+
geom_vline(xintercept=272,lwd=2)
p=p+geom_vline(xintercept=71,color="red")+
geom_vline(xintercept=309,color="red")
p=p+ylab("Hour")+theme_bw()
p=p+xlab("\nDay Of Year")+opts(legend.position="none")
p
ggsave("timeshift.pdf",p,width=6)


Figures created with Hadley Wickham’s ggplot2

ADJUSTMENT TO REDUCE VARIANCE IN THE TIME OF SUNRISE

How did they decide when and by how much to make the “daylight savings time” adjustment? There’s a nice visualization at http://visual.ly/daylight-saving-time-explained which suggests that daylight savings time was chosen in a way to keep the time of sunrise relatively constant throughout the year. Check out the chart above: the time of sunrise deviates from the “average sunrise” time less than the time of sunset deviates from the “average sunset” time. Compelling.

The creator of the visualization, who seems to go by the handle germanium, writes

I wanted to see the effect of daylight saving time change on sunrise and sunset times. The data was taken from http://www.timeanddate.com and is for Chicago. The figure shows that daylight saving time change (marked by the DLS lines) keeps the sunrise time pretty much constant throughout the whole year, while making the sunset time change a lot. The spread of sunrise times for the whole year as measured by the standard deviation is 42 minutes, while for sunset times is 1:30 hours.

DON’T STORE SMALL CHANGE, PUT IT TO USE

A friend recently asked us what to do with his large and unintentional collection of foreign coins left over from many international trips. He was surprised to learn that currency exchanges won’t take them. Since hanging onto coins between foreign trips is annoying (*), we recommend the following three practices for putting your coins to purposeful use.

1) Give them to charity. There are collection boxes in most international airports. Once you know about them, you’ll see them everywhere. We took the pictures in this post on just one international trip.

2) Use them plus a credit card to buy something at an airport shop. A few bucks worth of foreign currency won’t buy anything interesting at a duty-free shop, however, the same shops will happily accept all your small change plus a credit card to make up the difference on a larger item. We often buy things we are going to use anyway, you know, like batteries and gin.

3) If you have former European currencies that are no longer circulating (Belgian franc, Deutsche Mark, Estonian kroon, Irish pound, Luxembourg franc, Maltese lire, Dutch Guilder, Austrian Schilling, Portuguese escudos, Slovak koruna, Slovenian tolar, Spanish pesetas und Cypriot pound), you’re not entirely out of luck. You can send them to euromoney24.com and ask that they be donated to charity or transferred to your bank account.

(*) We do hold on to bills, however, for countries we expect to revisit within a couple years

HIDDEN HINTS HELP DRIVERS

In response to last week’s surprisingly popular “how to tell which side the gas cap is on”, we received a number of emails, one by our friend and co-author Preston McAfee, who shares a tip [from this site] that also helps driving by letting you know in advance on which side your exit will be. The picture says it all.

Photo credit: http://shialabeowulf.tumblr.com/post/33670447154/99-life-hacks-to-make-your-life-easier

DRIVE THAT RENTAL CAR TO THE CORRECT SIDE OF THE PUMP

Somewhere along the road of life, we at Decision Science News learned that the little triangle next to the fuel gauge points to the gas-cap side of the car.

We’re not promising this works on every car, but it’s worked on every car we’ve rented.

Guess you’ll need to find some other occasion to practice your backing-up-while-turning skills.

A TOOL TO REPRESENT PROBABILITIES IN AN EASY-TO-UNDERSTAND WAY

We’ve written before about using information grids when communicating risks to the general public. We like them. Turns out they are also called pictographs and, as we learned from an email from Brian Zikmund-Fisher, icon arrays.

As Brian puts it

Iconarray.com is a free online tool that enables anyone to create icon array risk graphics (sometimes called pictographs), download the images, or even embed the graphics in web pages just the way you can embed YouTube videos.

To learn more, see my blog post at Risksense.org or just visit the site directly at iconarray.com.

The current demonstration version is sponsored by the University of Michigan Risk Science Center and the UM Center for Bioethics and Social Sciences in Medicine.

Here’s a glimpse at the user interface:

FACULTY POSITIONS IN ORGANIZATIONAL BEHAVIOR

There are quite a few JDM (Judgment and Decision Making) researchers at Yale. Have a look at http://jdm.som.yale.edu/people.htm.

The Yale School of Management is seeking additional faculty members at all levels in the area of organizational behavior. Ph.D./Ph.D. equivalent (or at the final stages of dissertation) and demonstrated potential for high quality research and teaching required. Interdisciplinary orientation and interest in theory and application is preferred. Appointments will be made for the 2013 – 2014 academic year.

To apply online, visit: http://mba.yale.edu/faculty/faculty_openings.shtml

Applications must be submitted electronically by November 7, 2012.

Yale is an equal opportunity, affirmative action employer and especially encourages applications from women and members of minority groups.

SCP AS PART OF THE APA SUMMER CONFERENCE, NOVEMBER 16, 2013 DEADLINE

The Society for Consumer Psychology (SCP) will hold its summer conference as part the 121st Annual Convention of the American Psychological Association (APA) from July 31st to August 4th 2013 at the Hawaii Convention Center. SCP (Division 23 of APA) represents consumer researchers and psychologists interested in a broad range of consumer research issues united by psychological theories. We are seeking competitive papers, working papers (posters), special session symposia, and skill building sessions. Diverse themes and methodological approaches are welcome. We especially welcome submissions that address topics related to addictive or excessive consumer behaviors (e.g., gambling, video-gaming, over-eating, compulsive buying, excessive use of social media), as well as research that addresses consumer welfare at the individual or societal level (e.g., materialism, sustainability, youth and family risk, food and health decision making).

All submissions must be made through the APA website by the November 16, 2012 deadline.

If you have any questions (or any trouble using the conference submission website), please feel free to contact the Division 23 conference chair: Rebecca Walker Naylor, The Ohio State University.

More Information on the SCP Summer Conference (PDF) | Conference Website

NOTE:
This is a small SCP conference, not the main SCP conference, which is February 28 – March 2, 2013 at Omni La Mansion del Rio Hotel, San Antonio. See http://www.myscp.org for more information.

DO RESEARCH ON COGNITION, MEMORY, AND DECISION MAKING ACROSS THE LIFESPAN

When Decision Science News was born, it was born at Columbia’s Center
for the Decision Sciences. Now CDS is hiring again.

Did you know that Decision Science News started while it’s editor was working at Columbia University’s Center for the Decision Sciences? It’s true.

Columbia University’s Center for the Decision Sciences (CDS) anticipates hiring a postdoctoral fellow for a period of a minimum one year with an immediate start date. The position includes a full time salary and health benefits, starting as early as October 15th, 2012 and continuing until January 31st, 2014, with the possibility of renewal.

The main responsibility will be to carry out research related to cognition and memory with an emphasis on decision-making and the construction of preferences across the lifespan, under the supervision of Professors Eric Johnson and Elke Weber. This position is open to candidates with behavioral research experience, data analysis and modeling skills (particularly structural equation models), and training in cognitive psychology or a related discipline, who have recently earned their PhD or who are expecting their doctorate in 2013, on a topic relevant to the psychology of decision making broadly defined. Training in neuropsychology as well as neuroscience and fMRI research would be a particularly valuable skill. Additionally experience with health- and cognitive function screening of older adults and experience with on-line research is also a plus.

The candidate should have experience with running complex structural equation models, factor analysis, and multiple group invariance testing. Experience using Mplus is useful and experience with R is critical. Knowledge of cognitive aging research, especially the distinction between fluid and crystallized intelligence, is desirable.

To apply, please send a CV, two letters of recommendation, reprints of published papers, and a cover letter describing your research interests. In your cover letter, please describe your research expertise, data analysis and modeling skills, neuropsychological and neuroscience skills, and computer skills (including any experience with online research).

Review of applications will start immediately and continue until the position is filled. Electronic applications (all parts as attachments to a single email) should be submitted to zeynep@decisionsciences.columbia.edu.

Columbia University is an Affirmative Action, Equal Opportunity Employer

OPEN LETTER URGES LABS TO REPLICATE RESULTS TO AVOID A LOOMING “TRAIN WRECK”

Daniel Kahneman issued an open letter to researchers doing social priming research, which has become the subject of skepticism after some studies were found to be fabricated and others were not able to be independently replicated. His letter offers advice to scholars about how to address the situation: Find out the truth through extensive replication and announce it.

The text of the letter is below:

From: Daniel Kahneman
Sent: Wednesday, September 26, 2012 9:32 AM
Subject: A proposal to deal with questions about priming effects

Dear colleagues,

I write this letter to a collection of people who were described to me (mostly by John Bargh) as students of social priming. There were names on the list that I could not match to an email. Please pass it on to anyone else you think might be relevant.

As all of you know, of course, questions have been raised about the robustness of priming results. The storm of doubts is fed by several sources, including the recent exposure of fraudulent researchers, general concerns with replicability that affect many disciplines, multiple reported failures to replicate salient results in the priming literature, and the growing belief in the existence of a pervasive file drawer problem that undermines two methodological pillars of your field: the preference for conceptual over literal replication and the use of meta-analysis. Objective observers will point out that the problem could well be more severe in your field than in other branches of experimental psychology, because every priming study involves the invention of a new experimental situation.

For all these reasons, right or wrong, your field is now the poster child for doubts about the integrity of psychological research. Your problem is not with the few people who have actively challenged the validity of some priming results. It is with the much larger population of colleagues who in the past accepted your surprising results as facts when they were published. These people have now attached a question mark to the field, and it is your responsibility to remove it.

I am not a member of your community, and all I have personally at stake is that I recently wrote a book that emphasizes priming research as a new approach to the study of associative memory – the core of what dual-system theorists call System 1. Count me as a general believer. I also believe in a point that John Bargh made in his response to Cleeremans, that priming effects are subtle and that their design requires high-level skills. I am skeptical about replications by investigators new to priming research, who may not be attuned to the subtlety of the conditions under which priming effects are observed, or to the ease with which these effects can be undermined.

My reason for writing this letter is that I see a train wreck looming. I expect the first victims to be young people on the job market. Being associated with a controversial and suspicious field will put them at a severe disadvantage in the competition for positions. Because of the high visibility of the issue, you may already expect the coming crop of graduates to encounter problems. Another reason for writing is that I am old enough to remember two fields that went into a prolonged eclipse after similar outsider attacks on the replicability of findings: subliminal perception and dissonance reduction.

I believe that you should collectively do something about this mess. To deal effectively with the doubts you should acknowledge their existence and confront them straight on, because a posture of defiant denial is self-defeating. Specifically, I believe that you should have an association, with a board that might include prominent social psychologists from other field. The first mission of the board would be to organize an effort to examine the replicability of priming results, following a protocol that avoids the questions that have been raised and guarantees credibility among colleagues outside the field.

The following is just an example of such a protocol:
* Assemble a group of five labs, where the leading investigators have an established reputation (tenure should perhaps be a requirement). Substantial labs with several students are the most desirable participants.
* Each lab selects a recent demonstration of a priming effect, which they consider robust and most likely to replicate.
* The board makes a public commitment to these five specific effects
* Set up a daisy chain of labs A-B-C-D-E-A, where each lab will replicate the study selected by its neighbor: B replicates A, C replicates B etc.
* Have the replicating lab send someone to see how subjects are run (hence the emphasis on recency – the experiments should be in the active repertoire of the original lab, so that additional subjects can be run with confidence that the same procedure is followed).
* Have the replicated lab send someone to vet the procedure of the replicating lab as it starts its work
* Run enough subjects to guarantee power (probably more than in the original study)
* Use technology (e.g. video) to ensure that every detail of the method is documented and can be copied by others.
* Pre-commit to publish the results, letting the chips fall where they may, and make all data available for analysis by others.

This is something you could do quickly, and relatively cheaply. The main costs are 10 trips, and funds to cover these costs would be easy to get (I have checked). You would have to be careful in selecting laboratories and results to maximize credibility, and every step of the procedure should be open and documented. The unusually high openness to scrutiny may be annoying and even offensive, but it is a small price to pay for the big prize of restored credibility.

Success (say, replication of four of the five positive priming results) would immediately rehabilitate the field. Importantly, success would also provide an effective challenge to the adequacy of outsiders’ replications. A publicly announced and open effort would be credible among colleagues at large, because it would show that you are sufficiently confident in your results to take a risk.

More ambiguous results would be painful, of course, but they would still protect the reputations of scholars who sincerely believe in their work – even if they are sometimes wrong.

The protocol I outlined is just an example of something you might do. The main point of my letter is that you should do something, and that you must do it collectively. No single individual will be able to overcome the doubts, but if you act as a group and avoid defensiveness you will be credible.

In response to Ed Yong’s article in Nature in which Kahneman’s letter is published, Norbert Schwarz, has written a response, saying “There is no empirical evidence that work in this area is more or less replicable than work in other areas.”

REFERENCE
Nobel laureate challenges psychologists to clean up their act