Thursday, October 30, 2014

googol's deepmind has stated that its goal is "solving intelligence"...,

technologyreview |  One of the great challenges of neuroscience is to understand the short-term working memory in the human brain. At the same time, computer scientists would dearly love to reproduce the same kind of memory in silico.

Today, Google’s secretive DeepMind start-up, which it bought for $400 million earlier this year, unveils a prototype computer that attempts to mimic some of the properties of the human brain’s short-term working memory. The new computer is a type of neural network that has been adapted to work with an external memory. The result is a computer that learns as it stores memories and can later retrieve them to perform logical tasks beyond those it has been trained to do.

DeepMind’s breakthrough follows a long history of work on short-term memory. In the 1950s, the American cognitive psychologist George Miller carried out one of the more famous experiments in the history of brain science. Miller was interested in the capacity of the human brain’s working memory and set out to measure it with the help of a large number of students who he asked to carry out simple memory tasks.

Miller’s striking conclusion was that the capacity of short-term memory cannot be defined by the amount of information it contains. Instead Miller concluded that the working memory stores information in the form of “chunks” and that it could hold approximately seven of them.

That raises the curious question: what is a chunk? In Miller’s experiments, a chunk could be a single digit such as a ‘4’, a single letter such as a ‘q’, a single word or a small group of words that together have some specific meaning. So each chunk can represent anything from a very small amount of information to a hugely complex idea that is equivalent to large amounts of information.

But however much information a single chunk represents, the human brain can store only about seven of them in its working memory.

Here is an example. Consider the following sentence: “This book is a thrilling read with a complex plot and lifelike characters.”

This sentence consists of around seven chunks of information and is clearly manageable for any ordinary reader.

By contrast, try this sentence: “This book about the Roman Empire during the first years of Augustus Caesar’s rein at the end of the Roman Republic, describes the events following the bloody Battle of Actium in 31 BC when the young emperor defeated Mark Antony and Cleopatra by comprehensively outmaneuvering them in a major naval engagement.”

This sentence contains at least 20 chunks. So if you found it more difficult to read, that shouldn’t be a surprise. The human brain has trouble holding this many chunks in its working memory.

In cognitive science, the ability to understand the components of a sentence and store them in the working memory is called variable binding. This is the ability to take a piece of data and assign it to a slot in the memory and to do this repeatedly with data of different length, like chunks.