Why Machine Intelligence is Very Hard Theo Pavlidis Distinguished Professor Emeritus Dept. of...

Why Machine Intelligence is Very Hard

Theo PavlidisDistinguished Professor Emeritus

Dept. of Computer Science

[email protected]

http://theopavlidis.com

2/29/2008 Machine Intelligence - CS talk 2

Limitations of Computers

• Some tasks (e.g. number factorization) are very hard for computers (unless it is proven that NP = P), but they are also very hard for humans.

• Some tasks that are quite easy for humans but very hard for computers.

• Examples: language translation, image analysis or understanding, speech recognition, game playing, etc. (Often grouped under Artificial Intelligence AI).

• Why are they hard?


The State of Machine Vision

• There have seen some successes, notably in industrial inspection and reading of printed text but a lot of problems remain open.

• Reading distorted text (CAPTCHA) is so hard that it is used as a security device.

• Content Based Image Retrieval (CBIR) is hopelessly behind content based text retrieval.

• Face recognition programs are known mainly for their failure to perform outside the laboratory.


CAPTCHA

• CompletelyAutomatedPublicTuring test to tellComputers andHumansApart


Content-based Image Retrieval(CBIR)

• Given an image find those that are similar to it from a data base of images. (If the images are labeled, the problem is reduced to text search.)

• Many systems have been advertised but they do well only on rather trivial queries.

• This should be contrasted with the success of text retrieval, not only Google but earlier programs such as the Unix grep.


Example - 1


Example - 2


Reasons for the Poor Results in Machine Vision and CBIR

• Images are represented by statistics of pixel values (e.g. color histogram, texture histogram, etc)

• Such statistics are unrelated to human perception.

• Papers describing CBIR methods use trivial queries (e.g. “show me all pictures with a lot of green”).


Perceptual versus Computational Similarity

• Two pictures may differ a lot in their pixel values but appear similar to a person. (“They have the same meaning”.)

• Two pictures may differ in very few pixels but they have different meaning. (Face portraits of two different people in front of the same background.)


Perceptual versus Computational Similarity

Perceptually close Pixel-wise close


Text versus Pictures

• In text files each byte (or two) is a numerical code for a character. Therefore strings of bytes correspond to words that carry semantic meaning.

• In pictures each byte (or group thereof) represents the color at a particular location (pixel). Pixels are quite far from the components that have a semantic meaning.


We do not that well in text!

• If it is hard to search for concepts unless we can map concepts into words.

• Example 1: Find all articles critical of the government policy in dealing with the banking crisis.

• Example 2: Find all articles about a dog named Lucy. Amongst the Google returns was an article with the phrase: “Lucy and I spent the weekend alone together. We have a dog named Kyler.”


Human Intelligence made simple

Input

Output

InputConcept


The Big Difference• The transformation of input to concept is a complex

process (binding), barely understood by neuroscientists. (In spite of claims to the opposite by some computer scientists.)

• It is hard to develop algorithms for a barely understood process.

• Humans can transform concepts into formal entities (words in a language) and then code them in computer readable form.

• Computers can deal with such formal input.


What Neuroscientist Say

• “Perceptions emerge as a result of reverberations of signals between different levels of the sensory hierarchy, indeed across different senses”. The author then goes on to criticize the view that “sensory processing involves a one-way cascade of information (processing)”

• Source: V.S. Ramachandran and S. Blakeslee Phantoms in the Brain, William Morrow and Company Inc., New York, 1998 (p. 56)


What Do You See?


Reading Demo - 1


Reading Demo - 1

Tentative binding on the letter shapes (bottom up) is finalized once a word is recognized (top down). Word shape and meaning over-ride early cues.


Reading Demo -2

New York State lacks proper facilities for the mentally III.

The New York Jets won Superbowl III. • Human readers may ignore entirely the shape of

individual letters if they can infer the meaning through context.


The Importance of Context

• “Human intelligence almost always thrives on context while computers work on abstract numbers alone. … Independence from context is in fact a great strength of mathematics.”

• Source: Arno Penzias Ideas and Information, Norton, 1989, p. 49.


The Challenges

• We need to replicate complex transformations that the (human/animal) brain has evolved to do over millions of years.

• We have to deal with the fact the processing is not unidirectional and also affected by other factors than the input (context). (Such factors cause visual illusions.)


A time scale

• The human visual system has evolved from animal visual systems over a period of more than 100 million years.

• Speech is barely over 100 thousand years old.• Written text is no more than 10 thousand years

old.


A note on brain models • There is a history for considering the latest

technology to be a model of the human brain, for example in the 16th century irrigations networks were considered to be models of the brain.

• If someone claims to have a machine modeling the human brain, ask how could the machine be modified to model the brain of a dog (since a dog cannot learn to write poetry, play chess, etc)?


A Note on Neural Nets

Is this a model of the brain?

As much as a table is a model of a dog.


Simplified model of a small part of the brain


A Dubious Approach

• “Training” on large numbers of samples has been used as a way out of finding a way to understand what is going on.

• But humans (and animals) do not need to be trained on large numbers of samples.

• Rats trained to distinguish between a square and a rectangle perform quite well when faced with skinnier rectangles. They have the concept of rectangle!


Distinguish Rectangles from SquaresThe Artificially Intelligent Approach

• Take a hundred (or more) pictures of rectangles and squares, compute several statistics on each picture and for each picture create a “feature” vector F. Then compute a vector W so that

F’W > 0 for squares andF’W < 0 for rectangles


Distinguish Rectangles from SquaresThe Natural Approach

• Find the outline of a shape (if one exists in a picture) and fit a rectangle to it. Then compute the aspect ratio of the rectangle. If it is near 1 (for some given tolerance), then it is called a square, otherwise a rectangle.

• Criticism: Method lacks generality!!!


No Generality in Nature

• The animal visual systems has many special areas for visual tasks (about 30 in the human case).

• We have already seen examples where “high level” (context) recognition takes quickly over the low level data processing.


Negator of Generality


The Learning Machine (neural net) Approach

• It has the appeal of getting something for nothing, so it is kept alive.

• We can “solve” a problem without really understanding it.

• Give a learning machine “enough” samples and a classifier will be found!!!

• (Forget about the rat who only needs two samples.)


Criteria for Choosing a Problem to Work on

• Context should either be known or not important.• Processing of the input should be relatively simple

(it should be clear what kind of information we need to extract).

• For an example relying heavily on context see: technology/BoxDimensions/overview.htm on my web site.

• Comments on major areas in the next few slides.


Speech Recognition

• Grammar driven models (using low level context) have been quite successful.

• High level context is even better. For example, matching a speech fragment to a name on a list.


Optical Character Recognition (OCR)

• Printed text characters have small shape variability and high contrast with the background. (CAPTCHA systems negate these properties)

• Spelling checkers (or ZIP code directories in postal applications) introduce low level context.


An example of heavy use of context

• Reading of the checks sent for payment to American Express.

• Because payments are supposed to be in full and the amount due is known, the number written on a check is analyzed to confirm whether it matches the amount due or not.

• (But direct payment is used more and more!)


An Aside: Why did OCR mature when the need for it was diminished?

• The algorithms used in the products of the 1990s were known earlier but they were too complex to be implemented effectively with the digital technology of earlier times.

• When computer hardware became cheap enough for good OCR, it also became cheap enough for PCs and the Internet.

• Keep this in mind in your business plans!


Face Recognition

• It took over forty years to built acceptable quality machines that recognize written symbols. What makes us think that we can solve the much more complex problem of distinguishing human faces?

• Neuroscientists point out that humans have special neural circuitry for face recognition.


How these two faces differ?


How about these two?


Face Recognition and Scalability

• The population samples in published studies are relatively small and include men and women of different races with different hairstyles, etc.

• I have never seen a study where all the subjects are similar. For example, white blond men between the ages of 20 and 30 with long hair and beards.

• Subjects in published studies are cooperative.


Face Detection

• Before proceeding with face recognition we need to find the faces in a picture (face detection)

• CMU has a web site where the public may submit pictures and they get back results with a green square overlaid on faces facing front and green pentagons of profiles.

• Results are not robust.


Glimpses from the Face Detection Gallery - 1


Glimpses from the Face Detection Gallery - 3

They got the wrong person


Concluding Remarks

• Before we try to built a machine to achieve a goal we must ask ourselves whether that goal is compatible with the laws of nature . (Not because “people can do it”.)

• While such laws are clear in Physics and Chemistry, there are not in the field of Computation except in some extreme cases.


Human Credulity - 1

• In spite of well understood laws of physics “inventors” persist in offering designs that violate them and they find takers.

• Therefore fundamental advances in Computer Science are likely to reduce but not to eliminate preposterous claims.


Human Credulity - 2

• 50 years ago Langmuir (in “Pathological Science”) debunked UFOs but also predicted that UFOs will be with us for a long time because it is too good a story for the news media to let go.

• The view of computers as giant brains that are able to out-think and replace humans is about as valid as visits by extraterrestrials, but it makes too good a story for the news media to let go.


The End

That’s all folks

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