Learning is growing: scientists investigate the links between memory and brain development

Bill Skaggs skaggs at bns.pitt.edu
Wed Sep 1 12:14:32 EST 1999

"John" <johnhkm at netsprintXXXX.net.au> writes (quoting a press release):

> In this issue, Benedikt Berninger, Alejandro Schinder, and Mu-ming Poo
> (University of California, San Diego) show that neurotrophins have more
> effect on weak synapses than strong ones. Measuring signal strength between
> pairs of nerve cells, they find that applying neurotrophins increases
> synapse strength dramatically if the initial signal is small. If the initial
> signal is already large, neurotrophins do not increase it much further. This
> work suggests neurotrophins strengthen nerve connections by "maturing"
> undeveloped synapses, leaving strong or "mature" synapses relatively
> unaffected. So learning may really be growing after all.

Am I missing something?  There seems to be a problem with the logic
here.  As far as I can see, the reasoning is:

Premise 1: Learning involves an increase in synaptic strength.
Premise 2: Growth involves an increase in synaptic strength.
Conclusion:  Learning is the same thing as growth.

This is an example of one of the classic logical fallacies, called the
"undistributed middle" if I remember correctly.  It's just like saying
the following:

Premise 1: Being stretched on the Rack makes a person taller.
Premise 2: Growing up makes a person taller.
Conclusion: Growing up is the same thing as being stretched on the

Why is it so common to see scientific work of indisputably high
quality (which this is) being described with press releases that are
sheer nonsense?

	-- Bill

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