The Structure and Function of Fish Schools
How do they do it? The question occurs naturally to anyone watching
a school of fish moving slowly over a reef in clear tropical water. Hundreds
of small silver fish glide in unison, more like a single organism than
a collection of individuals. The school idles along on a straight course,
then wheels suddenly; not a single fish is lost from the group.
Although schooling of fish is one of the most familiar forms of animal
social behaviour,
(First question: what do you expect the content/function of the next clause to be?)
until recently it was little understood, partly because of
the difficulty of observing minute changes of position and velocity in a
school under natural conditions.
It had been thought that each fish maintains its position in the school
chiefly by means of vision.
(Second question: What will the informational content of the next sentence be?)
Our work has shown that the lateral line, an
organ sensitive to transitory changes in water displacement, is as important
as vision.
The most appropriate format for this type of exercise seemed to be open
questions. I have chosen to encourage answers in the mother tongue, as this
allows more creativity on the students’ behalf and reduces spelling and
syntax errors which will make answer processing even more hazardous
than it already is. Open-ended answers are evaluated on the basis of
keywords taken to indicate a correct answer. Thus, in the answer to the
second question, the program must acknowledge as correct any sentences
containing the words inconnu, peu connu, ma1 compris.
This poses some problems, as there may well appear to be alternative
correct answers which had not been anticipated, or incorrect answers
which contain the expected keywords. There are three solutions to this
limitation of the software, the first of them being simply not to formulate
correction messages in too definitive a style. The second is to use the bookkeeping
facilities of the program to update the program with unexpected
correct answers that students may produce. Thirdly, by imposing a certain
form on the answer (for example, asking students to formulate their
answers as questions), it is possible to control syntactical complexity so that
a simple parsing algorithm can analyse the answers in more detail.