Let's now see whether page rank has
anything to do with how we remember things
and recall our past memories.
Quite clearly, search results ordered by
page rank have proved rather intuitive.
The success of Google itself is testament
to this fact.
Might the intuitive success of page rank
provide any insight into how we recall
things from memory.
In an interesting article in psychological
science in 2007 researchers tried to
figure this out through experiment.
What they did is they asked a lot of
people to form associations between words.
So people would be asked to name the first
word that comes to mind when hearing a
word like apple, for example.
Some people might say orange, in which
case a link would get created between the
word apple and the word orange.
If more people paired these two words,
this particular link would get stronger.
So in this manner, a semantic network was
created.
Such a semantic network is very similar to
the network of web pages linked by
hyperlinks.
That was the argument in this paper.
Next people were asked to form letter word
associations, very similar to the example
we discussed a while ago.
So what's the first word that comes to
mind when your given the letter A.
Maybe apple.
The question is.
Could the semantic network be used to
predict.
Which word comes to mind given a
particular letter.
The relationship to search is quite
simple.
In the web, when it's searching for words,
the semantic met...
Network on a searching for letters.
So the question is if your algorithm
retrieves a whole bunch of words starting
with the letter a, which one would it
order first.
Does page rank in this network, instead of
this network now, provide any clue?
Turns out that the human responses in
experiment two could be predicted very
well by page rank operating on the
semantic network.
Here is an example of the results of this
experiment.
What this says is that.
75 percent of the human responses, ended
up being within the top twenty percent
dial, of the ordering provided by the
Paydrag.
So clearly paydrag was mimicking.
The human response fared well.
The question is does this mean anything.
Is human memory similar to Google's
massive index with page reckoning on it,
what do you think?
Actually the answer is probably'no'.
For example, most of us are poor at
remembering facts.
Such as when was Napoleon's defeat at
Waterloo?
Google on the other hand is excellent at
retrieving exactly the correct fact.
Secondly, we often need context to augment
our recall.
For example, we might not recognize a work
colleague when we see them in a mall.
We simply can't place them in that
context.
Further, memories are linked in time.
For example, what one did the first thing
in the morning, and thereafter, and
thereafter, are all linked.
Another example might be an incident from
one's first day at school, college or
work.
When you put this two contexts together,
the incident and the day at work or
college get linked.
Finally, memories are fuzzy.
For example, can you recall every item in
your room?
Probably not.
The picture that you form in your mind is
very spars.
On the other hand.
Memories can be triggered by very sparse
matches, such as a mere smell, or a mere
face, can recall an entire incident or an
entire picture.
This does appear to suggest that the way
memory works is quite different from how
search works.
Later in this course we'll touch upon a
number of models which appear to be much
closer to how human memory works.
And quite different from search.
And we will also see how the AI
applications that exploit big data get
better and better when one uses memory
like mechanisms as oppose to search alone.