A study compared the accuracy of people and rats in predicting which
light would come on next. 80% it is the green light and 20% it is the
red light, purely at random. Rats figure out the green light comes on
more often and always pick the green light, being right 80% of the
time. People also recognize the green light is more likely, but also
see "patterns" so sometimes believe red is "due" and pick red,
reducing the accuracy to about 68%. This study is cited in the
following web page:
http://www.azstarnet.com/dailystar/printDS/30281.php

What is the primary reference for this study and a copy of the article.

Hello jhs1-ga,

The Kathy Kristof article you cite shows that she got her information
from a contact at the Russel Investment Group.

http://www.azstarnet.com/dailystar/printDS/30281.php
Kathy Kristof: 
Investors need a game plan, strategist says Kathy Kristof
Tucson, Arizona | Published: 07.18.2004

If investors would act a bit more like rats, they'd do much better in
the stock market, said Ernie Ankrim, chief investment strategist at
Russell Investment Group in Tacoma, Wash.


Searching for the source of the comparison made about the behavior of
rats and humans led to the original article on the Russell site as
well as a posting of the same article in a more recent newsletter. The
article includes a citation of the research report that is described
in the investment newsletter.

http://www.russell.com/ca/Education_Centre/Professor_Portfolio/Psychology.asp
Professor Portfolio:
Succeeding as Investors In Spite of Ourselves

https://secure.ingham.com/forms/Investor20051231.pdf
Russell Investment Group
Investor Newsletter ? 4th Quarter 2005


The research report cited by Russell is titled: The Left Hemisphere?s
Role in Hypothesis Formation. I was able to locate this document and
you can read it in its entirety. This journal article cites earlier
research on the maximizing and matching behaviors of animals. The most
relevant article is titled Matching, Maximizing, and Hill-climbing and
I?ve located a complete copy of this article for you as well.

http://www.jneurosci.org/cgi/content/full/20/6/RC64
The Journal of Neuroscience, 2000, 20:RC64:1-4
RAPID COMMUNICATION
The Left Hemisphere's Role in Hypothesis Formation 

ABSTRACT 
In a probability guessing experiment, subjects try to guess which of
two events will occur next. Humans tend to match the frequency of
previous occurrences in their guesses. Animals other than humans tend
to maximize or always choose the option that has occurred the most
frequently in the past. Investigators have argued that frequency
matching results from the attempt of humans to find patterns in
sequences of events even when told the sequences are random. There is
independent evidence that the left hemisphere of humans houses a
cognitive mechanism that tries to make sense of past occurrences. We
performed a probability guessing experiment with two split-brain
patients and found that they approximated frequency matching in their
left hemispheres and approached maximizing in their right hemispheres.
We obtained a conceptual replication of that finding on patients with
unilateral damage to either the left or right hemisphere. We conclude
that the neural processes responsible for searching for patterns in
events are housed in the left hemisphere.

In a variety of such guessing experiments, humans typically exhibit
frequency matching. That is if the lights to the two sides are
presented with probabilities p and (1   p), the subjects guess the two
lights with probabilities p and (1   p) (Humphreys, 1939 ; Estes, 1961
). The tendency to match frequency has intrigued investigators because
it is a nonoptimal strategy for this paradigm. Maximizing, or choosing
the most frequent option all of the time, yields more correct guesses
than matching as long as p   0.5. In other words, if the red light
occurs with a frequency of 70% and a green light occurs with a
frequency of 30%, overall accuracy will be highest if the subject
predicts red all of the time (maximizing). Frequency matching will
lead to correct answers 58% of the time (0.7 * 0.7 + 0.3 * 0.3).
Maximizing will lead to correct answers 70% of the time (0.7 * 1.0 +
0.3 * 0.0). Interestingly, most other animals maximize in such
paradigms (Hinson and Staddon, 1983 ). So why do humans choose a less
optimal strategy than rats? Our view is that humans believe there is a
pattern, even if told the sequence is random, and they attempt to
figure out the pattern. Any reasonable pattern hypothesized by the
subjects would have to match frequency if it were to be a correct
hypothesis. Perhaps animals other than humans adopt a more optimal
strategy than humans in this paradigm, because they are not as
hindered by the tendency to search for and posit causal hypotheses.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1347942
J Exp Anal Behav. 1983 November; 40(3): 321?331. 
doi: 10.1901/jeab.1983.40-321. 

Matching, maximizing, and hill-climbing
John M. Hinson and J. E. R. Staddon 

Abstract
In simple situations, animals consistently choose the better of two
alternatives. On concurrent variable-interval variable-interval and
variable-interval variable-ratio schedules, they approximately match
aggregate choice and reinforcement ratios. The matching law attempts
to explain the latter result but does not address the former.
Hill-climbing rules such as momentary maximizing can account for both.
We show that momentary maximizing constrains molar choice to
approximate matching; that molar choice covaries with pigeons'
momentary-maximizing estimate; and that the ?generalized matching law?
follows from almost any hill-climbing rule.

http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1347942&blobtype=pdf
Full text
Full text is available as a scanned copy of the original print
version. Get a printable copy (PDF file) of the complete article
(1.5M), or see the PubMed citation or the full text of some References
or click on a page below to browse page by page.


You can continue your explorations of the matching and maximizing
behaviors of humans, rats and other animals by following the links
that led me to the results for this question.

://www.google.com/search?hl=en&q=maximizing+matching+rats

Best wishes for your projects.

~ czh ~



SEARCH STRATEGY
research rats humans choosing red green lights
maximizing matching rats

Yes, I saw the source was the Russel report, so this answer probably
fits my question since I didn't rule that out.

I actually read the primary article, but cannot remember the citation.
It was not "matching behaviors" or "maximizing" as mentioned in the
Russell report.

"Humans tend to match the frequency of previous occurrences in their
guesses." I don't think anyone believes that is how humans make
choices. What humans do is recognize "patterns" - things tend to get
wet after thunder, bison will run over a cliff if stampeeded, every
fifth car is a chevy and the last four were fords,...

Humans have a hard time accepting randomness, so tend to instead
believe there is a pattern. Often this is helpful and an advantage. If
something really is random, though, falsely seeing a pattern is a
disadvantage.

The simplest situation that shows this disadvantage is a binary
choice, where one choice is "correct" with probability p > 0.5. Things
are randomized so either choice can be correct, but overall A is
correct with probability "p" and B is correct with probability (1 -
p).

If things really are random, the best strategy is to always guess A,
and be correct with probability "p". No other strategy is better.

Humans tend to believe there is a pattern, or that "B" is "overdue" is
there are several A in a row. So, occasionally humans will guess B,
reducing the probability of being correct.

This was part of a longer article, and wasn't really the main point.
So it wasn't directly related to the title of the article. The wall
street journal quoted it a couple of years ago, giving the author.
From that I found the actual article, but can't remember the author's
name.

Oh, well.

I really doubt if rats can discrimante between red and green...

Check eg http://www.ratbehavior.org/RatVision.htm#ColorPerception

What came in my mind to me was skinner and his pigeons. He did same
equally experiments. Also, Kahneman and Tversky have shown that human
beeings tend to have some biases in decision making.

Sorry for not answering your initial question, but I find it really
hard to believe this is possible.

Free hint: Try to contact the author of the article, kathy.kristof@latimes.com

Good luck.

Yes, I suppose rats are color blind. Maybe it was 2 levers & guess
which one would have the light go on next. Left one lights 80%, right
one 20%. The only article I could find on this refered to red/green,
so obviously mis-quoting whoever did the work with the rats.

Given a binary choice, where the correct answer is totally random but
one choice is more likely, say 80%/20%, rats & humans both recognize
which is more likely. Rats can't go any farther & always guess
whichever is more likely, so they are right 80% of the time.

Humans "see a pattern" and will sometimes guess the less likely
choice. The probability of being right with thish choice is 20% (or 1
- p), so if they choose the superior choice with probability q, then
they are right with probability p*q + (1-q)*(1-p) < p, so the rats
win.

This isn't the "matching" strategy mentioned in the Russell Investment
Group. It is our "pattern recognition" apparatus that serves us so
well in a trick situation.