January 25, 2014

Are you smart enough to work at Google by William Poundstone

Are you smart enough to work at Google by William Poundstone

[Trick questions, Zen-like riddles, insanely difficult puzzles, and other devious interviewing technique you need to know to get a job anywhere in the new economy]

What number comes next?
10,90, 60,90,70,66,

Forget math. Spell out the numbers in the plain English, which gives the following
ten(3), nine(4), sixty(5), ninety(6), seventy(7), sixty-six (8),
The numbers are in order of how many letters are in their names. The next number should have 9 letters in it. Secondly, look more closely. Ten is not the only number you can spell with three letters. There is one, two and six, but ten is the largest one in three letter block. Same with the rest of the numbers listed in the series. If both conditions needs to meet, the second better answer is ninety-six (if the number should be less than 100). If there is no limitation, the best answer is ten googol.

The word - googole - appeared in the 1940 book that Kasner wrote with James Newman, Mathematics and Imagination. Nine-year old Milton Sirotta and his brother Edwin were talking a stroll one day with their uncle in the New Jersey Palisades. The uncle was Edward Kasner, a Columbia mathematician already what famous as the first Jew to gain tenure in the science at that Ivy league institution. Kasner entertained the boys by talking about a topic calculated to appeal to bookish nine-year olds, namely the number that could be written as a ‘1’ followed by 100 zeros. Kasner challenged his nephew to invent a name for the number. Milton’s suggestion was ‘googol’.

The story behind Google’s google name.
Sean (Anderson) and Larry (Page) were in their office, using the whiteboard, trying to think up aa good name - something that related to the indexing of an immense amount to data. Sean verbally suggested the googolplex and Larry respond verbally with the shortened form, googol (both words are specific large numbers - Googolplex is 10 raised to the power of googol). Sean was seated at his computer so he executed a search of the internet domain name registry database to see it the newly suggested name was still available for registration and use. Sean is not an infallible speller, and he made the mistake of searching for the name spelled as google.com which he found ot be available. Larry liked the name and within hours, he took the step of registering the name google.com for himself and Sergey.

What comes next in the series?
The series is the letters of the alphabet in a silly code. A as a capital letter, is made of three straight lines. Encode that as SS. B can be written as one straight line and two curved (SCC). C has single curve, D has one straight and one curve (SC). So E being the next letter, which is four straight lines, the next sequence is SSSS

When there is a wind blowing, does a round-trip by plan take more time, less time or the same?
In general, you wouldn’t expect the wind to be following exactly in the direction of travel, nor exactly at ninety degrees to it. The direction would be somewhere in between. You can break the wind’s velocity down into headwind-tailwind and crosswind components. The point is that both components increase the round-trip time. The best wind for round-trip air travelers is no wind at all.

You and your neighbor are holding yard sales on the same day. Both of you plan to sell the exact same item. You plan to put your item on sale for $100. The neighbor had informed you that he is going to put his on sale for $40. The items are in identical condition. What do you, assuming you are not on especially friendly with this neighbor?

The best answer is buy neighbor's item and hide your item until the first one sells,. then put the second item on sale at a reduced price, according to how late in the day it is.

[Google does spell checking: it is not based on dictionaries; it is based on word usage statistics of the entire internet., which is why Google knows how to correct my name, misspelled and Microsoft Word does not.]

You want to have Tim’s number, but you cannot ask him directly. Ann is sitting between you and Tim can pass your note once and Tim can also do the same. Ann who sitting in the middle, should not get to know Tim’s number while passing the message across. What is the strategy.
Answer: Tim, call my phone using the number you got.

If you had a stack of pennies as tall as the Empire state building, could you fit them all in one room?

You have ten thousand Apache servers, and one day to generate $1 million. What do you do?

There are two rabbits, speedy and Sluggo. When they run a 100 meter race, Speedy crosses the finish line while Sluggo ist at 90 meter mark. (Both run at a constant speed). Now we match up in a handicapped race. Speedy has to start from 10 meters behind the start (and run 110 meters) while Sluggo starts at the usual mark and runs 100 meters. Who will win?

Answer: Speedy.

There are three women in bathing suites. Two are sad and one is happy. The sad women are smiling. The happy woman is crying. Explain the situation.

Answer: They are beauty contestants.

What is the next number in the series

1 1
2 1
1 2 1 1
1 1 1 2 2 1

Answer: This is the look and say sequence. described by the mathematician John Horton Conway in 1986. Except for the first line, each inventories the line above it. Second line says, there is 1 one. 3rd line says, there are 2 ones. 4th line says, there is 1 two and there is 1 one. 5th line says, 1 one, 1 two, 2 ones. So the next in series should be 3 1 2 2 1 1 (3 ones, 1 two, 2 ones).

1. How do you put a giraffe into a refrigerator?
Correct Answer: Open the refrigerator, put in the giraffe, and close the door. This question tests whether you tend to do simple things in an overly complicated way.
2. How do you put an elephant into a refrigerator?
Did you say, Open the refrigerator, put in the elephant, and close the refrigerator?
Wrong Answer.
Correct Answer: Open the refrigerator, take out the giraffe, put in the elephant and close the door. This tests your ability to think through the repercussions of your previous actions.

3. The Lion King is hosting an animal conference. All the animals attend.... except one. Which animal does not attend?
Correct Answer: The Elephant. The elephant is in the refrigerator. You just put him in there. This tests your memory.
Okay, even if you did not answer the first three questions correctly, you still have one more chance to show your true abilities.
4. There is a river you must cross but it is used by crocodiles, and you do not have a boat. How do you manage it?
Correct Answer: You jump into the river and swim across. Have you not been listening? All the crocodiles are attending the Animal Meeting. This tests whether you learn quickly from your mistakes.

Ref links

This was a course taught at MIT by Bill Jacobs and Curtis Fonger, focusing on technical questions for software engineers.

Other Quiz questions:
100 prisoners are each locked in a room
Who Is the Surgeon?
Monty Hall problem
Dining philosophers problem

January 20, 2014

Average is over by Tyler Cowen

Average is over by Tyler Cowen

Powering America beyond the age of the great stagnation

The imbalance in technological growth will have some surprising implications. For instance, workers more and more will come to be classified into two categories. They key question will be: Are you good at working with intelligent machines or not? Are your skills a complement to the skills of the computer, or is the computer doing better without you? Worst of all, are you competing against the computer?

There is a joke that a “modern textile mill employ only a man and a dog - the man to feed the dog and the dog to keep the man away from the machines”.

In today’s global economy here is what is scarce:

Quality land and natural resource
Intellectual property or good ideas about what should be produced
Quality labor with unique skills

We are high returns to resource owners, such as the new resource millionaires and billionaires of Brazil, Russia, Canada and Australia and similarly huge revenues for intellectual property giants like Apple and other innovators in that sector.

General Philip M. Breedlove, US Air force vice chief of staff, works with military drones. He recently said, “Our number one manning problem in the air force is manning our unmanned platforms”. According to air force, keeping an unmanned Predator drone in the air for 24 hours requires about 168 workers laboring in the background. A larger drone, such as the Global Hawk surveillance drone, needs about 300 people working in the background to make the mission feasible.

Mark Zuckerberg of Facebook fame was a psychology major and insights from psychology helped him make Facebook into  a more appealing and alluring site.

Top 1 % of America comes from finance background.  There has been Steve Jobs, Mark Zuckerberg, and Bill gates, but finance is a common source of riches within the very highest tier of earners. To give one extreme but illuminating example, in 2007 the top 25 hedge-fund earners pulled in more income than all the CEOs of the S&P 500 put together.  The modern financial sector has computers, computerized trading, arbitrage, super-rapid communications, and computerized risk assessment at its core.

If you have an unusual ability to spot, recruit and direct those who work well with computers, even if you don’t work well with computers, the contemporary world will make you rich. If we look at the increase in the shares of income going to the top tenth of a percent from 1979 to 2005, executives, managers, supervisors and financial professional captured 70% of those gains.

The better the world is at measuring value, the ,more demanding a lot of career paths will become. it is easier to buy companies than to replicate their recruiting or lure away their best employees. A recent report laid out how these acquisitions work: Engineers are worth half a million to one million’, said Vaughan Smith, Facebook’s VP of corporate development.

It is well known from personal psychology and confirmed by experience, that women are on average more conscientious than men. They are more likely to follow instructions and orders with exactness and without resentment. That means, better jobs and higher wages for a lot of women in this new world of work, without a comparable upgrade for for a lot of men.

Let us draw up a simple list of some important characteristics in technology advanced modern workspace.

Exactness of execution becomes more important relative to an accumulated mass of brute force.
Consistent coordination over time is a significant advantage
Morale is extremely important to motivate production and cooperation.

We have been seeing what is called, labor market polarization’ a concept that is most closely identified with MIT labor economist David Autor. It means, that workers are to an increasing degree, falling into two camps. They either to very well in labor market or they don’t do well at all.

There are some particular reasons why employment opportunities are growing in finance, law and consulting. Today, laws are more numerous and more complicated than in my father’s day and that increase the demand for lawyers, at least at the top end of the market. A global economy means larger supply chains and consultants can help business track and evaluate those complex operation. Finance is growing in part because the promise of bailouts encourages banks to become larger and also take on more risk.

Freshly minted students form prominent colleges will seek out jobs that reward a high g-factor or high general intelligence. That mean,s finance, law and consulting. The students are productive fairly quickly, they make good contacts with other smart people and they can demonstrate that that are smart for future employment prospects. Working to exercise and demonstrate their general intelligence is in fact the main thing they are good for and moving beyond this can be quite a few years. Consider consulting. Take a smart but inexperienced and underspecified 22 year old and ask, “Can you draw up an effective PowerPoint for me? or can you research this new accounting practice or new congressional law? or even what is wrong with this business plan? You might get some pretty good answers.

Human-computer teams are the best teams
The person working the smart machine does have to be expert in the task at hand
Below some critical level of skill, adding a man to the machine will make the team less effective than the machine working alone
Knowing one’s own limit is more important than it used to be

Virginia Tech's Math Emporium is an open, 60,000-square-foot laboratory with 550 Macintosh computers serving more than 8,000 math students each semester. The facility occupies renovated, leased space in an off-campus shopping mall. (See Figure 1.) Spurred by the need to accommodate thousands of students and to improve learning outcomes, the emporium opened in 1997 to improve the quality of large-enrollment math courses in the face of growing resource constraints - http://www.educause.edu/research-and-publications/books/learning-spaces/chapter-42-virginia-tech-math-emporium

We are standing at an unusual point in the history of science. Many Americans who are not scientist can follow some of the basic results of say, evolutionary biology or Einstein’s theory of general relativity

Science itself, in many areas , moving beyond the frontiers of ready intelligibility. For at least three reasons, a lot of science will become harder to understand.

1. In some scientific areas, problems are becoming more complex and susceptible to simple, intuitive, big breakthroughs

2. The individual scientific contribution is becoming more specialized , a trend that has been running for centuries and is unlikely stop

3. One day soon, intelligent machines will become formidable researchers in their right.

It might be called the age of genius machines and it will be the people who work with them that will rise. One day soon we will look back and see that we produced two nations, a fantastically successful nation, working in the technologically dynamic sector and everyone else. Average is over.


January 19, 2014

Impulse by David Lewis

Impulse by David Lewis
Why we do what we do without knowing why we do it.

Impulse lie at the root of most personal and social problems ranging from obesity, alcohol and drug abuse, overspending, unwanted pregnancies, smoking, emotional problems, dysfunctional relationships and school underachievement to a failure in achieving cherished life goals.

Impulse as per physicist, impulse is an indefinitely large force that acts for a very short time that brings about a change of momentum. In this book I argue that virtually everything we say and we do between waking and sleeping can be considered impulsive in that the vast majority of those actions occur mindlessly rather than mindfully.

As per Ellen Langer, when we accept an impression or a piece of information at face value... the that impression settles unobtrusively into our minds.... most of us don’t reconsider what we mindlessly accepted earlier...the mindless individual is committed to one predetermined use of the information and other possible use or applications are not explored.

Within a few hundredths of a second of meeting someone for the first time we usually get a sense of whether we like them, are sexually attracted to them are indifferent to them or are uncomfortable in their presence. The feeling of not liking someone without being able to explain why was summed up by a 17th century student named Thomas Brown in a verse dedicated to his university dean Dr. Thomas Fell:

I do not like thee, Doctor Fell
The reason why I cannot tell;
But this I know and know full well,
I do not like thee Doctor Fell.

The impulsive power of smell

We all possess an entirely personal ‘smell signature’ It is this unique smell that enables bloodhounds to track specific individuals, even in crowded urban environment. Our smell signature comprises a blend of skin, hair and glandular secretions, food and drink choices, odors in our surroundings and any perfume, after-shave or deodorant we use. But the most distinctive odor of all tends to be sweat. On its own this is capable of triggering impulsive sexual desire. The German sexologist Richard Kraft Ebbing, for example, described a ‘voluptuous young peasant man’ who boasted how he had ‘seduced quite a considerable number of chaste girls without difficulty by wiping his armpits with his handkerchief while dancing and then using this handkerchief to wipe the face of his dancing partner.

In the presence of a pleasant odor people were impulsively regarded as more likeable than when viewed with an unpleasant odor being present. Heart rate slowed in the presence of a pleasant odor and increased with an unpleasant one. Today the same fear of offensive body odor and a desire t make oneself sexually attractive and desirable are two main reasons why the manufacture and sale of perfumes and cosmetics has become a $280 billion a year global industry.

In Roman era, Civert and ambergris were esp. popular among leisured classes and given the importance of vanilla as an aphrodisiac it is interesting to note that the name of this spice is a diminutive of the Latin word vagina. When, during the 16th century, Sheikh al-Nefzawi of Tunia wrote one of the world’s earliest sex manuals, it was no coincidence he titled it ‘The Perfumed Garden’.

One substance used in modern male grooming products is androstenediol, a chemical structurally related to testosterone, the hormone produced in the tests which is found in male sweat and urine. Dr. David Benton of University College, Swansea, a researcher in this field found that females reacted more strongly to the hormone during the middle of their menstrual cycle, when it is caused them to assess their own mood as more submissive. “Sexual attraction relies on many factors including personality, social skills, past experience and present situation. If everything else is suitable then an odor may make a small difference but the product of an aerosol spray is unlikely to be the difference but the product of an aerosol spray is unlikely to be the predominant influence and compensate for other feelings.

So is pure French jasmine essence, reportedly the world’s most expensive perfume, really worth up to $300 a gram? More generally what effect does a woman wearing any sort of perfume have on the men around her? The answer seems to depend on how she is dressed. That is what research by Dr. Robert Baron of Purdue University suggests. In his tests, when assistant dressed smartly the perfume made seem cold and unromantic. When she wore the perfume with jeans and a T-shirt, however, the men’s impulse response was to regard her as warm and romantic. So the response that perfume evokes depends not just on our sense of smell but also the context in which it is worn.

In 1973 the American psychologist Philip Kotler, Professor of Marketing at Northwestern University, coined the term, atmospherics to describe the conscious planning of atmosphere to contribute to the buyer’s purchasing propensity and predicted that atmospherics is likely to play a growing role in the unending search of firms for differential advantage. Today even moderately sized supermarkets allocate space to an in-store bakery despite the fact that it is far more convenient and cost-effective for a central bakery to serve a number of stores. Managers know that by stimulating hunger pangs, the smell of freshly baked bread encourages people to buy not just bread but also other food, even frozen products.

In laundry section of a supermarket, shoppers exposed to the scent of freshly laundered sheets not only buy more detergents but also splash out on impulse purchases of products claiming to whiten whites or leave linen smelling like a spring morning.  One company has injected the smell of coconut into the shops of a British travel agent, because some sustain oils smell of coconut and the aroma is said to help trigger memories of past holidays and so encourage shoppers to book fresh ones.

In supermarket the sale of laundry products significantly increased when a fresh, lemony aroma was combined with the sound of freshly laundered sheets being folded. This, the promoters of the system claim, triggers associations with the comfort, safety and warmth of home. Perhaps by recalling childhood memories of helping mother with the weekly wash.

The impulsive power of sounds

Dr. M. Morrison of the department of marketing at Monash University says, “Music communicates with our hearts and minds; it serves as a powerful connection into our emotions. Music is versatile, it has the ability to relax or invigorate. Music is memorable, it can transport us in an instant to places we want to be. Retailers can use specifically programmed music to create links to past experience. Music can be critical components of store atmosphere and plays a role in purchase decision making process. As per the study conducted, under 25 spending more time shopping when exposed to easy listening music while those over 25 thought they had been in the store longer than when top 40 music was played.

Impulse purchases of the most expensive wines increased when Mozart, Bach and Vivaldi were played. Music preference, they found, are determined by age rather than sex of the shopper. Middle aged (25-49) shoppers spent more and shopped longer when foreground music was played whereas older shoppers shopped longer and purchased more when background music was playing.

Risk-taking personality

John Coates of university of Cambridge in his recent study, measured the length of male high-frequency traders second and fourth digits. They found that the traders appetite for risk taking could be accurately predicted by comparing the length of these two fingers. Research has shown that men who are impulsive risk takers have a ration of less than 1 if the length of their index finger (second digit) is divided by their ring finger (fourth digit). This has been dubbed the 2D:4D ratio. The ratio differs reliable by sex with males typically having a lower 2D:4D on their right hand than on their left hand. How much is less than 1, which much risk taking and how much more than 1 shows how much they are risk averse.

In a moment when, James Joyce wrote in Ulysses: “I asked him with my eyes to ask again yes, and then he asked me would I yes.... and first I put my arms around him yes and drew him down to me as he could feel my breasts all perfume yes and his heart was going like mad and yes I said yes I will yes”..

In his 1971 book, The Attraction Paradigm, social psychologist Don Byrne proposed that while shared appear to form the basis of attraction, the number of similar views mater less than proportion of similar to dissimilar attitude. So consistent is this finding that one can express the probability of liking or disliking occurring in terms of the following mathematical formula
Y=5.44X =6.62

This states that the best way of predicting the extent of liking (Y) between two people is to multiply the proportion of similar attitudes (X) by 5.44 and then add 6.62. Two people who share 50% of the same views will score 9.34 (0.585.44 + 6.62).

In my lab we use eye-tracking technology to examine how men and women look at one another’s bodies. In lab conditions, men and women look at the semi-naked bodies of members of the opposite sex in a very different ways. Single heterosexual man viewing a bikini clad women; he started at her thighs and buttocks and then moved up to her groin, breasts and neck. His eyes travelled back to her breasts and up & down her abdomen and legs. He concluded at the point where her left hand points downward to her groin.  The woman by contrast, began her inspection at man's face, returning there on three subsequent occasions. Next her eyes travelled up and down his chest and abdomen, halting just above his groin. She then examined his chest muscles and left arm m his right arm, his left armpit and then his face again. She repeated her examination of his torso, stopping as before, just above the pubic region. Finally her eyes moved back his left arm, before ending where she began, at his face.  When individuals being viewed are fully clothed a different pattern of gaze occurs with more attention being directed towards face.

The most reliable of those fertility cues is the waist-to-hip ratio (WHR) which, Dr. Devendra Singh contends, is the key to being regarded by males as fertile and fanciable. Between 19820 and 1980s, every Miss America winner has a WHR between .72 and 0.69.

The scarcity effect of physical desire was first investigated by Dr. James Pennebaker of the University of Virginia who was intrigued by a line in songwriter Baker Knight 1970s hit: Don’t all the girls get prettier at closing time”. This read, Ain’t it funny, ain’t it strange, the way a man’s opinion change when the stars to face that lonely night.’

Ten practical ways to beat the overrating impulse

1. Eat from smaller plates and bowls. Because we eat with our eyes as much as with our mouth, using smaller plates and bowls is a quick and easy way to reduce the number of calories consumed at each meal.

2. When drinking anything but water, use a tall narrow glass rather than a short wide one. This is known as horizontal-vertical illusion. The eye is fooled by the height of the liquid in the glass and ignores the width.

3. Eat with chopsticks, rather than a knife and fork, obliges you to take smaller mouthfuls and eat more slowly.

4. Put ice in your drink. Because the body has to use energy to beat up the beverages, around 1 calorie per ounce of fluid is consumed.

5. Eat alone. We eat significantly more when dining in company than eating alone.

6. When dining out in an up-market restaurant be aware of the effects of soft lights and classical music. Both encourages you to linger longer and so eat or drink considerably more than you realize.

7. Get a good night sleep.

8. Avoid shopping for food when hungry

9. If you have sweets or chocolates in the office, place them in opaque containers rather than clear ones and at a distance form, rather than directly on, your desk.

10. When snacking on popcorn in the cinema, use your other hand (right-hand person use left hand vice versa). If so, consumption will be less.

Inside World's most powerful selling machine:

Just walk into a supermarket, we become participants in what Jeff Chester, director of the US based Center for Digital Democracy has called a ‘marketing technological arms race. Everything we see, hear, smell, taste or touch is the result of millions of dollars worth of research, design and planning.

The first products we typically see on entering a supermarket are fresh fruits and vegetables. It is done so for two reasons. First because they make both the store and the products themselves look fresh and attractive. Fruits and vegetables look better in natural light, just as meat and fish look tired in anything but a clean white light. Furthermore they subtly convey a sense of freshness and naturalness, evoking images not of vast and soulless food processing plants but of open green fields and cloudless blue skies. The second and chief reason is to make the shopper more likely to grab a trolley than reach for a basket. Because a trolley holds more it encourages shoppers to buy more. By making the task of moving purchases around far easier it encourages shoppers to impulse-buy more.

Another factor retailer must take into account when stacking shelves is known as the invariant right. A possible explanation for this is that the left hemisphere of the brain controls the right side of the body and this hemisphere is associated with an approach response and positive emotions. Shoppers tend to stay on the right as they stroll down both supermarket aisles and high street pavements. It is for this reason that in a well-designed airport, travelers drifting toward the departure gate will find the fast-food restaurants on their left and the gifts shops on their right. Both are in position most likely to encourage impulse purchases: while people may be prepared to cross a lane of pedestrian traffic when hungry they will rarely do so to buy a magazine or souvenir.

Research has shown that when we walk down an aisle we look mainly at shelves not at eye level but slightly lower. This is because when walking past shelves, a shopper’s gaze is directed between 15 & 30 degrees downward, mainly as a result of the weight and shape of the head and how it is supported by the spine. This is the prime position for high margin impulse purchases. Lower prices lower profit products go with down to floor level or upwards so as to be out reach to all but the tallest or more agile shopper.

Going deeper into the store we come across products termed destination goods or known value items (KVI). KVIs include such core grocery lines and weekly staples as milk, bread and baked beans. Supermarkets call these traffic generators because they have to be purchased frequently and are the most price-sensitive. While the average shopper’s awareness of prices tends to be limited, most do know the price of these regularly bought items and so are able to make comparison between rival stores. By ensuring the price of benchmark KVI is kept artificially low, by selling at or even below the cost, supermarkets are able to present all their products as great value for money.

On counters displaying clothes, high-margin items such as expensive and exotic foods, enticing gifts, must-have gadgets, these products are frequently laid out in such a way as to exploit the power of what is called the triangular balance. it is based on the fact that your eye will always go straight to the center of a picture says Karl McKeever. ‘Here, they put the biggest , tallest products with the highest profit margin in the center of the each shelf and arrange the other sizes around them to make it look attractive. When you look at the triangle on the shelf, your eyes goes straight to the middle and the most expensive box. It is used everywhere and it is very effective.

In fashion areas of stores, tables are often positioned next to clothes racks to allow customers to handle the items; Younger shoppers esp. are drawn more towards scuffed-up displays of cloths because this suggests they are popular. When the piles of garments appear overly neat, by contrast, it sends a message that no one else is interested in buying them.

Disordered piles and mounds of products are more likely to attract buyers than neatly ordered displays. There is a natural reluctance on the part of most shoppers to be the first to interfere with the symmetry of perfectly stacked items of food or ordered lines of fruit in an elegant display. Most products are handled many times by browsers before being purchased. The average lipstick, for example, is examined 6 to 8 times before it leaves the store and a greeting card 25 times.

Research has shown that the main limit on exercising our willpower is willpower itself. By exerting self-control in one situation we diminish our capacity to do so in another.
(See, how Ulysses listened, but escaped unhurt with Sirens’ Song - http://www.youtube.com/watch?v=LtiPgvTRrdk)

For more than 3 centuries, worries about one type of impulse above all others dominated the lives of many adults and ruined the lives of their children. That impulse is masturbation. Fear of the supposed consequence of what they called self-abuse led parents, doctors and ministers of church to seek ways of eliminating the practice by means of extremely cruel and humiliating.
The anonymous author of Hippolytus Redivius (1644) regarded it as a remedy against the dangerous allurements of women.

The idea that a conflict exists between impulses and self-control between passion and reason as the Greek philosophers put it. Socrates suggests that weakness of will cannot exist since no one would willingly act against his or her better judgment. Hunger, thirst, fatigue, addiction and sexual arousal all create the desire to satisfy a physical need, by eating, drinking, sleeping, taking drugs, or having sex. Called ‘visceral drives’ they can lead to impulses which undermine long-term goals.