20
Y. J. WEmS
In an analysis of the effects of vertical and median superior frontal
removal on touch learning Wells (1965a) has shown that these operations
increase the number but do not alter the pattern of errors in tactile
discriminations, and concludes from a variety of training and retention
experiments that vertical lobe removal has only quantitative and
no qualitative effects. Wells’s interpretation of the tactile results is
that the amplification effect of the vertical lobe is due to the addition of
further storage units to the learning system, which thus has a greater
chance of dominating other factors determining the sign of response.
In support of this he cites the survey of Muntz et al. (1962) of the effect’s
of vertical lobe removal in visual experiments. These authors point out
that the consequences of the operation are minimal in situations
(massed trials, simultaneous discriminations, series of trials without
rewards or punishments) where factors other than past experience of the
shapes to be distinguished are minimally liable to cause fluctuations in
the level of attack. At the moment there is little to choose between
the various views of the mode of action of the vertical lobe, which in
any case have much in common. This is an active field in which experimental results and anatomical findings are still rapidly accumulating.
111. ANNELIDS
Some of the earliest experiments on invertebrate learning were made
with tubiculous polychaete worms, because of their dramatic response
to passing shadows. A number of papers on the subject had appeared
by the end of that first decade of this century. Since then, interest in
worm learning has been intermittent, with most of the literature
concerned with T-maze learning by earthworms. Earthworms, since
they normally live underground in the dark, do not perform well
in open well-lit T-mazes, and the general impression created has
until recently been that annelids learn rather slowly. An apparent
exception was Copeland’s (1930) training experiment with Nereis
wirens Sars, which learned to reverse a normally negative response to
light, coming out of its tube to be fed after only five trials. After fifty
trials the worm was retrained to emerge in response to a light-off
signal in four trials, and in a succession of further reversals performance improved until one-trial reversals were achieved. Recent work
has confirmed that nereid worms, and N . wirens in particular, can sometimes learn quite rapidly. The exact conditions of the experiment are
critical, and one is left with the impression that a great deal of time and
effort has sometimes been wasted (particularly with earthworms) in
attempts to make annelids generate data under inappropriate conditions.
Y. J. WEmS
In an analysis of the effects of vertical and median superior frontal
removal on touch learning Wells (1965a) has shown that these operations
increase the number but do not alter the pattern of errors in tactile
discriminations, and concludes from a variety of training and retention
experiments that vertical lobe removal has only quantitative and
no qualitative effects. Wells’s interpretation of the tactile results is
that the amplification effect of the vertical lobe is due to the addition of
further storage units to the learning system, which thus has a greater
chance of dominating other factors determining the sign of response.
In support of this he cites the survey of Muntz et al. (1962) of the effect’s
of vertical lobe removal in visual experiments. These authors point out
that the consequences of the operation are minimal in situations
(massed trials, simultaneous discriminations, series of trials without
rewards or punishments) where factors other than past experience of the
shapes to be distinguished are minimally liable to cause fluctuations in
the level of attack. At the moment there is little to choose between
the various views of the mode of action of the vertical lobe, which in
any case have much in common. This is an active field in which experimental results and anatomical findings are still rapidly accumulating.
111. ANNELIDS
Some of the earliest experiments on invertebrate learning were made
with tubiculous polychaete worms, because of their dramatic response
to passing shadows. A number of papers on the subject had appeared
by the end of that first decade of this century. Since then, interest in
worm learning has been intermittent, with most of the literature
concerned with T-maze learning by earthworms. Earthworms, since
they normally live underground in the dark, do not perform well
in open well-lit T-mazes, and the general impression created has
until recently been that annelids learn rather slowly. An apparent
exception was Copeland’s (1930) training experiment with Nereis
wirens Sars, which learned to reverse a normally negative response to
light, coming out of its tube to be fed after only five trials. After fifty
trials the worm was retrained to emerge in response to a light-off
signal in four trials, and in a succession of further reversals performance improved until one-trial reversals were achieved. Recent work
has confirmed that nereid worms, and N . wirens in particular, can sometimes learn quite rapidly. The exact conditions of the experiment are
critical, and one is left with the impression that a great deal of time and
effort has sometimes been wasted (particularly with earthworms) in
attempts to make annelids generate data under inappropriate conditions.