Category: issue 14 – Alan Turing – The Genius Who Gave Us The Future

Computers that read emotions

by Matthew Purver, Queen Mary University of London

One of the ways that computers could be more like humans – and maybe pass the Turing test – is by responding to emotion. But how could a computer learn to read human emotions out of words? Matthew Purver of Queen Mary University of London tells us how.

Have you ever thought about why you add emoticons to your text messages – symbols like 🙂 and :-@? Why do we do this with some messages but not with others? And why do we use different words, symbols and abbreviations in texts, Twitter messages, Facebook status updates and formal writing?

In face-to-face conversation, we get a lot of information from the way someone sounds, their facial expressions, and their gestures. In particular, this is the way we convey much of our emotional information – how happy or annoyed we’re feeling about what we’re saying. But when we’re sending a written message, these audio-visual cues are lost – so we have to think of other ways to convey the same information. The ways we choose to do this depend on the space we have available, and on what we think other people will understand. If we’re writing a book or an article, with lots of space and time available, we can use extra words to fully describe our point of view. But if we’re writing an SMS message when we’re short of time and the phone keypad takes time to use, or if we’re writing on Twitter and only have 140 characters of space, then we need to think of other conventions. Humans are very good at this – we can invent and understand new symbols, words or abbreviations quite easily. If you hadn’t seen the 😀 symbol before, you can probably guess what it means – especially if you know something about the person texting you, and what you’re talking about.

Emoticons image by Gino Crescoli from Pixabay

But computers are terrible at this. They’re generally bad at guessing new things, and they’re bad at understanding the way we naturally express ourselves. So if computers need to understand what people are writing to each other in short messages like on Twitter or Facebook, we have a problem. But this is something researchers would really like to do: for example, researchers in France, Germany and Ireland have all found that Twitter opinions can help predict election results, sometimes better than standard exit polls – and if we could accurately understand whether people are feeling happy or angry about a candidate when they tweet about them, we’d have a powerful tool for understanding popular opinion. Similarly we could automatically find out whether people liked a new product when it was launched; and some research even suggests you could even predict the stock market. But how do we teach computers to understand emotional content, and learn to adapt to the new ways we express it?

One answer might be in a class of techniques called semi-supervised learning. By taking some example messages in which the authors have made the emotional content very clear (using emoticons, or specific conventions like Twitter’s #fail or abbreviations like LOL), we can give ourselves a foundation to build on. A computer can learn the words and phrases that seem to be associated with these clear emotions, so it understands this limited set of messages. Then, by allowing it to find new data with the same words and phrases, it can learn new examples for itself. Eventually, it can learn new symbols or phrases if it sees them together with emotional patterns it already knows enough times to be confident, and then we’re on our way towards an emotionally aware computer. However, we’re still a fair way off getting it right all the time, every time.

This article was first published on the original CS4FN website and a copy can be found on Pages 16-17 of Issue 14 of the CS4FN magazine, “The genius who gave us the future“. You can download a free PDF copy below, and download all of our free magazines and booklets from our downloads site.

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EPSRC supports this blog through research grant EP/W033615/1.

Software for Justice

by Paul Curzon, Queen Mary University of London (originally published in 2011)

A jury is given misleading information in court by an expert witness. An innocent person goes to prison as a result. This shouldn’t happen, but unfortunately it does and more often than you might hope. It’s not because the experts or lawyers are trying to mislead but because of some tricky mathematics. Fortunately, a team of computer scientists at Queen Mary, University of London are leading the way in fixing the problem.

The Queen Mary team, led by Professor Norman Fenton, is trying to ensure that forensic evidence involving probability and statistics can be presented without making errors, even when the evidence is incredibly complex. Their solution is based on specialist software they have developed.

Digital fingerprint image by ar130405 from Pixabay

Many cases in courts rely on evidence like DNA and fibre matching for proof. When police investigators find traces of this kind of evidence from the crime scene they try to link it to a suspect. But there is a lot of misunderstanding about what it means to find a match. Surprisingly, a DNA match between, say, a trace of blood found at the scene and blood taken from a suspect does not mean that the trace must have come from the suspect.

Forensic experts talk about a ‘random match probability’. It is just the probability that the suspect’s DNA matches the trace if it did not actually come from him or her. Even a one-in-a-billion random match probability does not prove it was the suspect’s trace. Worse, the random match probability an expert witness might give is often either wrong or misleading. This can be because it fails to take account of potential cross-contamination, which happens when samples of evidence accidentally get mixed together, or even when officers leave traces of their own DNA from handling the evidence. It can also be wrong due to mistakes in the way the evidence was collected or tested. Other problems arise if family members aren’t explicitly ruled out, as that makes the random match probability much higher. When the forensic match is from fibre or glass, the random match probabilities are even more uncertain.

DNA helix image by Gerd Altmann from Pixabay

The potential to get the probabilities wrong isn’t restricted to errors in the match statistics, either. Suppose the match probability is one in ten thousand. When the experts or lawyers present this evidence they often say things like: “The probability that the trace came from anybody other than the defendant is one in ten thousand.” That statement sounds OK but it isn’t true.

The problem is called the prosecutor fallacy. You can’t actually conclude anything about the probability that the trace belonged to the defendant unless you know something about the number of potential suspects. Suppose this is the only evidence against the defendant and that the crime happened on an island where the defendant was one of a million adults who could have committed the crime. Then the random match probability of one in ten thousand actually means that about one hundred of those million adults match the trace. So the probability of innocence is ninety-nine out of a hundred! That’s very different from the one in ten thousand probability implied by the statement given in court.

Norman Fenton’s work is based around a theorem, called Bayes’ theorem, which gives the correct way to calculate these kinds of probabilities. The theorem is over 250 years old but it is widely misunderstood and, in all but the simplest cases is very difficult to calculate properly. Most cases include many pieces of related evidence – including evidence about the accuracy of the testing processes. To keep everything straight, experts need to build a model called a Bayesian network. It’s like a graph that maps out different possibilities and the chances that they are true. You can imagine that in almost any court case, this gets complicated awfully quickly. It is only in the last 20 years that researchers have discovered ways to perform the calculations for Bayesian networks, and written software to help them. What Norman and his team have done is develop methods specifically for modelling legal evidence as Bayesian networks in ways that are understandable by lawyers and expert witnesses.

Norman and his colleague Martin Neil have provided expert evidence (for lawyers) using these methods in several high-profile cases. Their methods help lawyers to determine the true value of any piece of evidence – individually or in combination. They also help show how to present probabilistic arguments properly.

Unfortunately, although scientists accept that Bayes’ theorem is the only viable method for reasoning about probabilistic evidence, it’s not often used in court, and is even a little controversial. Norman is leading an international group to help bring Bayes’ theorem a little more love from lawyers, judges and forensic scientists. Although changes in legal practice happen very slowly (lawyers still wear powdered wigs, after all), hopefully in the future the difficult job of judging evidence will be made easier and fairer with the help of Bayes’ theorem.

If that happens, then thanks to some 250 year-old maths combined with some very modern computer science, fewer innocent people will end up in jail. Given the innocent person in the dock could one day be you, you will probably agree that’s a good thing.

This post was originally published in 2011 on our old CS4FN website and a copy can also be found on pages 18 and 19 in the Alan Turing issue of the CS4FN magazine, issue 14. You can download a free PDF copy of the magazine below along with our entire back issue of magazines and booklets at our downloads site.

Further reading in justice

Edie Schlain Windsor and same sex marriage – Edie was a computer scientist whose marriage to another woman was deemed ineligible for certain rights provided (at that time) only in a marriage between a man and a woman. She fought for those rights and won.

Edie Schlain Windsor and same sex marriage

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EPSRC supports this blog through research grant EP/W033615/1.

Keeping secrets on the Internet – encryption keeps your data safe

By Ben Stephenson, University of Calgary

How do modern codes keep your data safe online? Ben Stephenson of the University of Calgary explains

When Alan Turing was breaking codes, the world was a pretty dangerous place. Turing’s work helped uncover secrets about air raids, submarine locations and desert attacks. Daily life might be safer now, but there are still threats out there. You’ve probably heard about the dangers that lurk online – scams, identity theft, viruses and malware, among many others. Shady characters want to know your secrets, and we need ways of keeping them safe and secure to make the Internet work. How is it possible that a network with so many threats can also be used to securely communicate a credit card number, allowing you to buy everything from songs to holidays online?

The relay race on the Internet

When data travels over the Internet it is passed from computer to computer, much like a baton is passed from runner to runner in a relay race. In a relay race, you know who the other runners will be. The runners train together as a team, and they trust each other. On the Internet, you really don’t know much about the computers that will be handling your data. Some may be owned by companies that you trust, but others may be owned by companies you have never heard of. Would you trust your credit card number to a company that you didn’t even know existed?

Computer encryption padlock image by OpenClipart-Vectors from Pixabay

The way we solve this problem is by using encryption to disguise the data with a code. Encrypting data makes it meaningless to others, so it is safe to transfer the data over the Internet. You can think of it as though each message is locked in a chest with a combination lock. If you don’t have the combination you can’t read the message. While any computer between us and the merchant can still view or copy what we send, they won’t be able to gain access to our credit card number because it is hidden by the encryption. But the company receiving the data still needs to decrypt it – open the lock. How can we give them a way to do it without risking the whole secret? If we have to send them the code a spy might intercept it and take a copy.

Keys that work one way only

The solution to our problem is to use a relatively new encryption technique known as public key cryptography. (It’s actually about 40 years old, but as the history of encryption goes back thousands of years, a technique that’s only as old as Victoria Beckham counts as new!) With this technique the code used to encrypt the message (lock the chest) is not able to decrypt it (unlock it). Similarly, the key used to decrypt the message is not able to encrypt it. This may sound a little bit odd. Most of the time when we think about locking a physical object like a door, we use the same key to lock it that we will use to unlock it later. Encryption techniques have also followed this pattern for centuries, with the same key used to encrypt and decrypt the data. However, we don’t always use the same key for encrypting (locking) and decrypting (unlocking) doors. Some doors can be locked by simply closing them, and then they are later unlocked with a key, access card, or numeric code. Trying to shut the door a second time won’t open it, and similarly, using the key or access code a second time won’t shut it. With our chest, the person we want to communicate with can send us a lock only they know the code for. We can encrypt by snapping the lock shut, but we don’t know the code to open it. Only the person who sent it can do that.

We can use a similar concept to secure electronic communications. Anyone that wants to communicate something securely creates two keys. The keys will be selected so that one can only be used for encryption (the lock), and the other can only be used for decryption (the code that opens it). The encryption key will be made publicly available – anyone that asks for it can have one of our locks. However, the decryption key will remain private, which means we don’t tell anyone the code to our lock. We will have our own public encryption key and private decryption key, and the merchant will have their own set of keys too. We use one of their locks, not ours, to send a message to them.

Turning a code into real stuff

So how do we use this technique to buy stuff? Let’s say you want to buy a book. You begin by requesting the merchant’s encryption key. The merchant is happy to give it to you since the encryption key isn’t a secret. Once you have it, you use it to encrypt your credit card number. Then you send the encrypted version of your credit card number to the merchant. Other computers listening in might know the merchant’s public encryption key, but this key won’t help them decrypt your credit card number. To do that they would need the private decryption key, which is only known to the merchant. Once your encrypted credit card number arrives at the merchant, they use the private key to decrypt it, and then charge you for the goods that you are purchasing. The merchant can then securely send a confirmation back to you by encrypting it with your public encryption key. A few days later your book turns up in the post.

This encryption technique is used many millions of times every day. You have probably used it yourself without knowing it – it is built into web browsers. You may not imagine that there are huts full of codebreakers out there, like Alan Turing seventy years ago, trying to crack the codes in your browser. But hackers do try to break in. Keeping your browsing secure is a constant battle, and vulnerabilities have to be patched up quickly once they’re discovered. You might not have to worry about air raids, but codes still play a big role behind the scenes in your daily life.

Here’s another article from the author, Ben Stephenson: 100,000 frames – quick draw: how computers help animators create.

100,000 frames – quick draw: how computers help animators create

The ‘Keeping secrets on the internet‘ article was first published on the original CS4FN website and there’s a copy on pages 4-5 of the Alan Turing issue (#14) of the CS4FN magazine. You can download a free PDF of the magazine below, along with all of our other free material at our downloads site.

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EPSRC supports this blog through research grant EP/W033615/1.

Chocoholic Subtraction – make an edible calculating Turing machine

Chocoholic Subtraction

by Paul Curzon, Queen Mary University of London

A Turing machine can be used to do any computation, as long as you get its program right. Let’s create a program to do something simple to see how to do it. Our program will subtract two numbers.

A delicious uneven tower of broken chocolate bars with dark chocolate, white chocolate and milk chocolate.
Image by Enotovyj from Pixabay

The first thing we need to do is to choose a code for what the patterns of chocolates mean. To encode the two numbers we want to subtract we will use sequences of dark chocolates separated by milk chocolates, one sequence for each number. The more dark chocolates before the next milk chocolate the higher the number will be. For example if we started with the pattern laid out as below then it would mean we wanted to compute 4 – 3. Why? Because there is a group of four dark chocolates and then after some milk chocolates a group of three more.

M M M D D D D M M D D D M M M M …

(M = Milk chocolate, D = Dark chocolate)

Coloured flat circular lollipops with swirly spiral pattern
Image by Denis Doukhan from Pixabay

Here is a program that does the subtraction if you follow it when the pattern is laid out
like that. It works for any two numbers where the first is the bigger. The answer is given
by the final pattern. Try it yourself! Begin with a red lolly and follow the table below.
Start at the M on the very left of the pattern above.

 

Instructions table for Chocolate Turing Machine

From the above starting pattern our subtraction program would leave a new pattern:

M M M D M M M M M M M M M M M …

There is now just a single sequence of dark chocolates with only one chocolate in it.
The answer is 1!

Try lining up some chocolates and following the instructions yourself to see how it works.

This article was originally published on the CS4FN website and a copy can also be found on page 11 of Issue 14 of CS4FN, “Alan Turing – the genius who gave us the future”, which can be downloaded as a PDF, along with all our other free material, here: https://cs4fndownloads.wordpress.com/

 

 

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EPSRC supports this blog through research grant EP/W033615/1.

Chocolate Turing Machines – edible computing

by Paul Curzon, Queen Mary University of London

Could you make the most powerful computer ever created…out of chocolates? It’s actually quite easy. You just have to have enough chocolates (and some lollies). It is one of computer science’s most important achievements.

A delicious looking box of chocolates
Image by congerdesign from Pixabay

Imagine you are in a sweet factory. Think big – think Charlie and the Chocolate Factory. A long table stretches off into the distance as far as you can see. On the table is a long line of chocolates. Some are milk chocolate, some dark chocolate. You stand in front of the table looking at the very last chocolate (and drooling). You can eat the chocolates in this factory, but only if you follow the rules of the day. (There are always rules!)

The chocolate eating rules of the day tell you when you can move up and down the table and when you can eat the chocolate in front of you. Whenever you eat a chocolate you have to replace it with another from a bag that is refilled as needed (presumably by Oompa-Loompas).

You also hold a single lolly. Its colour tells you what to do (as dictated by the rules of the day, of course). For example, the rules might say holding an orange one means you move left, whereas a red one means you move right. Sometimes the rules will also tell you to swap the lolly for a new one.

The rules of the day have to have a particular form. They first require you to note what lolly you are holding. You then check the chocolate on the table in front of you, eat it and replace it with a new one. You pick up a lolly of the colour you are told. You finally move left, move right or finish completely. A typical rule might be:

If you hold an orange lolly and a dark chocolate is on the table in front of you, then eat the chocolate and replace it with a milk one. Swap the lolly for a pink one. Finally, move one place to the left.

A shorthand for this might be: if ORANGE, DARK then MILK, PINK, LEFT.

You wouldn’t just have one instruction like this to follow but a whole collection with one for each situation you could possibly be in. With three colours of lollies, for example, there are six possible situations to account for: three for each of the two types of chocolate.

As you follow the rules you gradually change the pattern of chocolates on the table. The trick to making this useful is to make up a code that gives different patterns of chocolates different meanings. For example, a series of five dark chocolates surrounded by milk ones might represent the number 5.

See Chocoholic Subtraction for a set of rules that subtracts numbers for you as a result of shovelling chocolates into your face.

Our chocolate machine is actually a computer as powerful as any that could possibly exist. The only catch is that you must have an infinitely long table!

By powerful we don’t mean fast, but just that it can compute anything that any other computer could. By setting out the table with different patterns at the start, it turns out you can compute anything that it is possible to compute, just by eating chocolates and following the rules. The rules themselves are the machine’s program.

This is one of the most famous results in computer science. We’ve described a chocoholic’s version of what is known as a Turing machine because Alan Turing came up with the idea. The computer is the combination of the table, chocolates and lollies. The rules of the day are its program, the table of chocolates is its memory, and the lollies are what is known as its ‘control state’. When you eat chocolate following the rules, you are executing the program.

Sadly Turing’s version didn’t use chocolates – his genius only went so far! His machine had 1s and 0s on a tape instead of chocolates on a table. He also had symbols instead of lollies. The idea is the same though. The most amazing thing was that Alan Turing worked out that this machine was as powerful as computers could be before any actual computer existed. It was a mathematical thought experiment.

So, next time you are scoffing chocolates at random, remember that you could have been doing some useful computation at the same time as making yourself sick.

This article was originally published on the CS4FN website and a copy can also be found on page 10-11 of Issue 14 of CS4FN, “Alan Turing – the genius who gave us the future”, which can be downloaded as a PDF, along with all our other free material, here: https://cs4fndownloads.wordpress.com/

Related Magazine …

EPSRC supports this blog through research grant EP/W033615/1.