Chapter 6 Introduction to Neural Networks



6.1 Introduction

Artificial Neural Networks are relatively crude electronic models based on the neural structure of the brain. The brain basically learns from experience. It is natural proof that some problems that are beyond the scope of current computers are indeed solvable by small energy efficient packages. This brain modeling also promises a less technical way to develop machine solutions. This new approach to computing also provides a more graceful degradation during system overload than its more traditional counterparts.

These biologically inspired methods of computing are thought to be the next major advancement in the computing industry. Even simple animal brains are capable of functions that are currently impossible for computers. Computers do rote things well, like keeping ledgers or performing complex math. But computers have trouble recognizing even simple patterns much less generalizing those patterns of the past into actions of the future.

Now, advances in biological research promise an initial understanding of the natural thinking mechanism. This research shows that brains store information as patterns. Some of these patterns are very complicated and allow us the ability to recognize individual faces from many different angles. This process of storing information as patterns, utilizing those patterns, and then solving problems encompasses a new field in computing. This field, as mentioned before, does not utilize traditional programming but involves the creation of massively parallel networks and the training of those networks to solve specific problems. This field also utilizes words very different from traditional computing, words like behave, react, self-organize, learn, generalize, and forget.


6.2 History of Artifical Neural Networks

The study of the human brain is thousands of years old. With the advent of modern electronics, it was only natural to try to harness this thinking process. The first step toward artificial neural networks came in 1943 when Warren McCulloch, a neurophysiologist, and a young mathematician, Walter Pitts, wrote a paper on how neurons might work. They modeled a simple neural network with electrical circuits.

Reinforcing this concept of neurons and how they work was a book written by Donald Hebb. The Organization of Behavior was written in 1949. It pointed out that neural pathways are strengthened each time that they are used.

As computers advanced into their infancy of the 1950s, it became possible to begin to model the rudiments of these theories concerning human thought. Nathanial Rochester from the IBM research laboratories led the first effort to simulate a neural network. That first attempt failed. But later attempts were successful. It was during this time that traditional computing began to flower and, as it did, the emphasis in computing left the neural research in the background.

Yet, throughout this time, advocates of "thinking machines" continued to argue their cases. In 1956 the Dartmouth Summer Research Project on Artificial Intelligence provided a boost to both artificial intelligence and neural networks. One of the outcomes of this process was to stimulate research in both the intelligent side, AI, as it is known throughout the industry, and in the much lower level neural processing part of the brain.

In the years following the Dartmouth Project, John von Neumann suggested imitating simple neuron functions by using telegraph relays or vacuum tubes. Also, Frank Rosenblatt, a neuro-biologist of Cornell, began work on the Perceptron. He was intrigued with the operation of the eye of a fly. Much of the processing which tells a fly to flee is done in its eye. The Perceptron, which resulted from this research, was built in hardware and is the oldest neural network still in use today. A single-layer perceptron was found to be useful in classifying a continuous-valued set of inputs into one of two classes. The perceptron computes a weighted sum of the inputs, subtracts a threshold, and passes one of two possible values out as the result. Unfortunately, the perceptron is limited and was proven as such during the "disillusioned years" in Marvin Minsky and Seymour Papert's 1969 book Perceptrons.

In 1959, Bernard Widrow and Marcian Hoff of Stanford developed models they called ADALINE and MADALINE. These models were named for their use of Multiple ADAptive LINear Elements. MADALINE was the first neural network to be applied to a real world problem. It is an adaptive filter which eliminates echoes on phone lines. This neural network is still in commercial use.

Unfortunately, these earlier successes caused people to exaggerate the potential of neural networks, particularly in light of the limitation in the electronics then available. This excessive hype, which flowed out of the academic and technical worlds, infected the general literature of the time. Disappointment set in as promises were unfilled. Also, a fear set in as writers began to ponder what effect "thinking machines" would have on man. Asimov's series on robots revealed the effects on man's morals and values when machines where capable of doing all of mankind's work. Other writers created more sinister computers, such as HAL from the movie 2001.

These fears, combined with unfulfilled, outrageous claims, caused respected voices to critique the neural network research. The result was to halt much of the funding. This period of stunted growth lasted through 1981.

In 1982 several events caused a renewed interest. John Hopfield of Caltech presented a paper to the national Academy of Sciences. Hopfield's approach was not to simply model brains but to create useful devices. With clarity and mathematical analysis, he showed how such networks could work and what they could do. Yet, Hopfield's biggest asset was his charisma. He was articulate, likeable, and a champion of a dormant technology.

At the same time, another event occurred. A conference was held in Kyoto, Japan. This conference was the US-Japan Joint Conference on Cooperative/Competitive Neural Networks. Japan subsequently announced their Fifth Generation effort. US periodicals picked up that story, generating a worry that the US could be left behind. Soon funding was flowing once again.

By 1985 the American Institute of Physics began what has become an annual meeting - Neural Networks for Computing. By 1987, the Institute of Electrical and Electronic Engineer's (IEEE) first International Conference on Neural Networks drew more than 1,800 attendees.

By 1989 at the Neural Networks for Defense meeting Bernard Widrow told his audience that they were engaged in World War IV, "World War III never happened," where the battlefields are world trade and manufacturing. The 1990 US Department of Defense Small Business Innovation Research Program named 16 topics which specifically targeted neural networks with an additional 13 mentioning the possible use of neural networks.

Today, neural networks discussions are occurring everywhere. Their promise seems very bright as nature itself is the proof that this kind of thing works. Yet, its future, indeed the very key to the whole technology, lies in hardware development. Currently most neural network development is simply proving that the principal works. This research is developing neural networks that, due to processing limitations, take weeks to learn. To take these prototypes out of the lab and put them into use requires specialized chips. Companies are working on three types of neuro chips - digital, analog, and optical. Some companies are working on creating a "silicon compiler" to generate a neural network Application Specific Integrated Circuit (ASIC). These ASICs and neuron-like digital chips appear to be the wave of the near future. Ultimately, optical chips look very promising. Yet, it may be years before optical chips see the light of day in commercial applications.


6.3 How Artificial Neural Networks Are Being Used

Artificial neural networks are undergoing the change that occurs when a concept leaves the academic environment and is thrown into the harsher world of users who simply want to get a job done. Many of the networks now being designed are statistically quite accurate but they still leave a bad taste with users who expect computers to solve their problems absolutely. These networks might be 85% to 90% accurate. Unfortunately, few applications tolerate that level of error.

While researchers continue to work on improving the accuracy of their "creations," some explorers are finding uses for the current technology.

In reviewing this state of the art, it is hard not to be overcome by the bright promises or tainted by the unachieved realities. Currently, neural networks are not the user interface which translates spoken works into instructions for a machine, but some day they will. Someday, VCRs, home security systems, CD players, and word processors will simply be activated by voice. Touch screen and voice editing will replace the word processors of today while bringing spreadsheets and data bases to a level of usability pleasing to most everyone. But for now, neural networks are simply entering the marketplace in niches where their statistical accuracy is valuable as they await what will surely come.

Many of these niches indeed involve applications where answers are nebulous. Loan approval is one. Financial institutions make more money by having the lowest bad loan rate they can achieve. Systems that are "90% accurate" might be an improvement over the current selection process. Indeed, some banks have proven that the failure rate on loans approved by neural networks is lower than those approved by some of their best traditional methods. Also, some credit card companies are using neural networks in their application screening process.

This newest method of seeking the future by analyzing past experiences has generated its own unique problems. One of those problems is to provide a reason behind the computer-generated answer, say as to why a particular loan application was denied. As mentioned throughout this report, the inner workings of neural networks are "black boxes." Some people have even called the use of neural networks "voodoo engineering." To explain how a network learned and why it recommends a particular decision has been difficult. To facilitate this process of justification, several neural network tool makers have provided programs which explain which input through which node dominates the decision making process. From that information, experts in the application should be able to infer the reason that a particular piece of data is important.

Besides this filling of niches, neural network work is progressing in other more promising application areas. The next section of this report goes through some of these areas and briefly details the current work. This is done to help stimulate within the reader the various possibilities where neural networks might offer solutions, possibilities such as language processing, character recognition, image compression, pattern recognition among others.


6.3.1 Language Processing

Language processing encompasses a wide variety of applications. These applications include text-to-speech conversion, auditory input for machines, automatic language translation, secure voice keyed locks, automatic transcription, aids for the deaf, aids for the physically disabled which respond to voice commands, and natural language processing.

Many companies and universities are researching how a computer, via ANNs, could be programmed to respond to spoken commands. The potential economic rewards are a proverbial gold mine. If this capability could be shrunk to a chip, that chip could become part of almost any electronic device sold today. Literally hundreds of millions of these chips could be sold.

This magic-like capability needs to be able to understand the 50,000 most commonly spoken words. Currently, according to the academic journals, most of the hearing-capable neural networks are trained to only one talker. These one-talker, isolated-word recognizers can recognize a few hundred words. Within the context of speech, with pauses between each word, they can recognize up to 20,000 words.

Some researchers are touting even greater capabilities, but due to the potential reward the true progress, and methods involved, are being closely held. The most highly touted, and demonstrated, speech-parsing system comes from the Apple Corporation. This network, according to an April 1992 Wall Street Journal article, can recognize most any person's speech through a limited vocabulary.

This works continues in Corporate America (particularly venture capital land), in the universities, and in Japan.


6.3.2 Character Recognition

Character recognition is another area in which neural networks are providing solutions. Some of these solutions are beyond simply academic curiosities. HNC Inc., according to a HNC spokesman, markets a neural network based product that can recognize hand printed characters through a scanner. This product can take cards, like a credit card application form, and put those recognized characters into a data base. This product has been out for two and a half years. It is 98% to 99% accurate for numbers, a little less for alphabetical characters. Currently, the system is built to highlight characters below a certain percent probability of being right so that a user can manually fill in what the computer could not. This product is in use by banks, financial institutions, and credit card companies.

Odin Corp., according to a press release in the November 4, 1991 Electronic Engineering Times, has also proved capable of recognizing characters, including cursive. This capability utilizes Odin's propriatory Quantum Neural Network software package called, QNspec. It has proven uncannily successful in analyzing reasonably good handwriting. It actually benefits from the cursive stroking.

The largest amount of research in the field of character recognition is aimed at scanning oriental characters into a computer. Currently, these characters requires four or five keystrokes each. This complicated process elongates the task of keying a page of text into hours of drudgery. Several vendors are saying they are close to commercial products that can scan pages.


6.3.3 Image (data) Compression

A number of studies have been done proving that neural networks can do real-time compression and decompression of data. These networks are auto associative in that they can reduce eight bits of data to three and then reverse that process upon restructuring to eight bits again. However, they are not lossless. Because of this losing of bits they do not favorably compete with more traditional methods.


6.3.4 Pattern Recognition

Recently, a number of pattern recognition applications have been written about in the general press. The Wall Street Journal has featured a system that can detect bombs in luggage at airports by identifying, from small variances, patterns from within specialized sensor's outputs. Another article reported on how a physician had trained a back-propagation neural network on data collected in emergency rooms from people who felt that they were experiencing a heart attack to provide a probability of a real heart attack versus a false alarm. His system is touted as being a very good discriminator in an arena where priority decisions have to be made all the time.

Another application involves the grading of rare coins. Digitized images from an electronic camera are fed into a neural network. These images include several angles of the front and back. These images are then compared against known patterns which represent the various grades for a coin. This system has enabled a quick evaluation for about $15 as opposed to the standard three-person evaluation which costs $200. The results have shown that the neural network recommendations are as accurate as the people-intensive grading method.

Yet, by far the biggest use of neural networks as a recognizer of patterns is within the field known as quality control. A number of automated quality applications are now in use. These applications are designed to find that one in a hundred or one in a thousand part that is defective. Human inspectors become fatigued or distracted. Systems now evaluate solder joints, welds, cuttings, and glue applications. One car manufacturer is now even prototyping a system which evaluates the color of paints. This system digitizes pictures of new batches of paint to determine if they are the right shades.

Another major area where neural networks are being built into pattern recognition systems is as processors for sensors. Sensors can provide so much data that the few meaningful pieces of information can become lost. People can lose interest as they stare at screens looking for "the needle in the haystack." Many of these sensor-processing applications exist within the defense industry. These neural network systems have been shown successful at recognizing targets. These sensor processors take data from cameras, sonar systems, seismic recorders, and infrared sensors. That data is then used to identify probable phenomenon.

Another field related to defense sensor processing is the recognition of patterns within the sensor data of the medical industry. A neural network is now being used in the scanning of PAP smears. This network is trying to do a better job at reading the smears than can the average lab technician. Missed diagnoses is a too common problem throughout this industry. In many cases, a professional must perceive patterns from noise, such as identifying a fracture from an X-ray or cancer from a X-ray "shadow." Neural networks promise, particularly when faster hardware becomes available, help in many areas of the medical profession where data is hard to read.


6.3.5 Signal Processing

Neural networks' promise for signal processing has resulted in a number of experiments in various university labs. Neural networks have proven capable of filtering out noise. Widrow's MADALINE was the first network applied to a real-world problem. It eliminates noise from phone lines.

Another application is a system that can detect engine misfire simply from the noise. This system, developed by Odin Corp, works on engines up to 10,000 RPMS. The Odin system satisfies the California Air Resources Board's mandate that by 1994 new automobiles will have to detect misfire in real time. Misfires are suspected of being a leading cause of pollution. The Odin solution requires 3 kbytes of software running on a Motorola 68030 microprocessor.


6.3.6 Financial

Neural networks are making big inroads into the financial worlds. Banking, credit card companies, and lending institutions deal with decisions that are not clear cut. They involve learning and statistical trends.

The loan approval process involves filling out forms which hopefully can enable a loan officer to make a decision. The data from these forms is now being used by neural networks which have been trained on the data from past decisions. Indeed, to meet government requirements as to why applications are being denied, these packages are providing information on what input, or combination of inputs, weighed heaviest on the decision.

Credit card companies are also using similar back-propagation networks to aid in establishing credit risks and credit limits.

In the world of direct marketing, neural networks are being applied to data bases so that these phone peddlers can achieve higher ordering rates from those annoying calls that most of us receive at dinner time. (A probably more lucrative business opportunity awaits the person who can devise a system which will tailor all of the data bases in the world so that certain phone numbers are never selected.)

Neural networks are being used in all of the financial markets - stock, bonds, international currency, and commodities. Some users are cackling that these systems just make them "see green," money that is. Indeed, neural networks are reported to be highly successful in the Japanese financial markets. Daiichi Kangyo Bank has reported that for government bond transactions, neural networks have boosted their hit rate from 60% to 75%. Daiwa research Institute has reported a neural net system which has scored 20% better than the Nikkei average. Daiwa Securities' stock prediction system has boosted the companies hit rate from 70% to 80%.


6.3.7 Servo Control

Controlling complicated systems is one of the more promising areas of neural networks. Most conventional control systems model the operation of all the system's processes with one set of formulas. To customize a system for a specific process, those formulas must be manually tuned. It is an intensive process which involves the tweaking of parameters until a combination is found that produces the desired results. Neural networks offer two advantages. First, the statistical model of neural networks is more complex that a simple set of formulas, enabling it to handle a wider variety of operating conditions without having to be retuned. Second, because neural networks learn on their own, they don't require control system's experts, just simply enough historical data so that they can adequately train themselves.

Within the oil industry a neural network has been applied to the refinery process. The network controls the flow of materials and is touted to do that in a more vigilant fashion than distractible humans.

NASA is working on a system to control the shuttle during in-flight maneuvers. This system is known as Martingale's Parametric Avalanche (a spatio-temporal pattern recognition network). Another prototype application is known as ALVINN, for Autonomous Land Vehicle in a Neural Network. This project has mounted a camera and a laser range finder on the roof of a vehicle which is being taught to stay in the middle of a windingroad.

British Columbia Hydroelectric funded a prototype network to control operations of a power-distribution substation that was so successful at optimizing four large synchronous condensors that it refused to let its supplier, Neural Systems, take it out.


6.4 Summary

In summary, artificial neural networks are one of the promises for the future in computing. They offer an ability to perform tasks outside the scope of traditional processors. They can recognize patterns within vast data sets and then generalize those patterns into recommended courses of action. Neural networks learn, they are not programmed.

Yet, even though they are not traditionally programmed, the designing of neural networks does require a skill. It requires an "art." This art involves the understanding of the various network topologies, current hardware, current software tools, the application to be solved, and a strategy to acquire the necessary data to train the network. This art further involves the selection of learning rules, transfer functions, summation functions, and how to connect the neurons within the network.

Then, the art of neural networking requires a lot of hard work as data is fed into the system, performances are monitored, processes tweaked, connections added, rules modified, and on and on until the network achieves the desired results.

These desired results are statistical in nature. The network is not always right. It is for that reason that neural networks are finding themselves in applications where humans are also unable to always be right. Neural networks can now pick stocks, cull marketing prospects, approve loans, deny credit cards, tweak control systems, grade coins, and inspect work.

Yet, the future holds even more promises. Neural networks need faster hardware. They need to become part of hybrid systems which also utilize fuzzy logic and expert systems. It is then that these systems will be able to hear speech, read handwriting, and formulate actions. They will be able to become the intelligence behind robots who never tire nor become distracted. It is then that they will become the leading edge in an age of "intelligent" machines.


[1]        Sima J. (1998). Introduction to Neural Networks, Technical Report No. V 755, Institute of Computer Science, Academy of Sciences of  the  Czech Republic

[2]        Kröse B., and van der Smagt P. (1996). An Introduction to Neural Networks. (8th ed.) University of Amsterdam Press, University of Amsterdam.