LEARNING BY MARINE INVERTEBRATES
26
Nereis pelagica responds to shadows, to sudden changes in light
intensity, and to mechanical shock, by a sudden contraction of the
body, whether inside its tube or partially emerged from it. With
trials at one minute intervals it rapidly habituates to any of these
stimuli (Fig. 15). The number of trials required varies with the stimulus
and increases with the interval between trials. Savings in retraining
experiments indicate that the rate of decay of habituation depends more
on the frequency and number of stimuli given than on the nature of the
stimulus; with trials at 3-min intervals the effect of training not to
7
5
-
Trials a1 1 min intervols
FIG 15. Latent habituation in Nerek pelagica. 0 shows the decline in response to a
sudden increase in light intensity from 0.08 to 33.9 ft candles. Trials a t 1-min
intervals, light on for 12 sec at each trial. T h e worms were dark adapted for 2 h
before the start of the experiment.
plots the results of a similar experiment
immediately following sixty trials (not shown here) a t which no response was
evoked by an increase in light intensity from 0.08 to 4.7 ft candles. The experiment
plotted 0 was done first, on worms not previously used for any habituation
experiment ; 0 follows 2 days later, with the same twelve worms. Points show the
average percentage reaction per group of five consecutive trials. (From Clark, 1960a.)
respond to sudden decreases in light intensity had disappeared in 17 h,
about three times as long as following similar training at 30-sec intervals
(Clark, 1960a, b).
Clark (1960a) also studied the effect of habituation to one class of
stimuli on habituation to a second. Habituation to mechanical shock,
a sudden decrease in light intensity or to a moving shadow appeared to
be independent, since the worms learned each at a different rate,
but when the matter was examined in more detail complex interactions
appeared between the various forms of light stimulus. It was found,
for example, that habituation to a sudden decrease in light intensity
26
Nereis pelagica responds to shadows, to sudden changes in light
intensity, and to mechanical shock, by a sudden contraction of the
body, whether inside its tube or partially emerged from it. With
trials at one minute intervals it rapidly habituates to any of these
stimuli (Fig. 15). The number of trials required varies with the stimulus
and increases with the interval between trials. Savings in retraining
experiments indicate that the rate of decay of habituation depends more
on the frequency and number of stimuli given than on the nature of the
stimulus; with trials at 3-min intervals the effect of training not to
7
5
-
Trials a1 1 min intervols
FIG 15. Latent habituation in Nerek pelagica. 0 shows the decline in response to a
sudden increase in light intensity from 0.08 to 33.9 ft candles. Trials a t 1-min
intervals, light on for 12 sec at each trial. T h e worms were dark adapted for 2 h
before the start of the experiment.
plots the results of a similar experiment
immediately following sixty trials (not shown here) a t which no response was
evoked by an increase in light intensity from 0.08 to 4.7 ft candles. The experiment
plotted 0 was done first, on worms not previously used for any habituation
experiment ; 0 follows 2 days later, with the same twelve worms. Points show the
average percentage reaction per group of five consecutive trials. (From Clark, 1960a.)
respond to sudden decreases in light intensity had disappeared in 17 h,
about three times as long as following similar training at 30-sec intervals
(Clark, 1960a, b).
Clark (1960a) also studied the effect of habituation to one class of
stimuli on habituation to a second. Habituation to mechanical shock,
a sudden decrease in light intensity or to a moving shadow appeared to
be independent, since the worms learned each at a different rate,
but when the matter was examined in more detail complex interactions
appeared between the various forms of light stimulus. It was found,
for example, that habituation to a sudden decrease in light intensity