Miller, Jelbert et al. Young children do not require perceptual-motor feedback to solve Aesop's Fable tasks

Aesop’s
Fable tasks – in which subjects drop objects into a water-filled tube to raise
the water level and obtain out-of-reach floating rewards – have been used to
test for causal understanding of water displacement in both young children and
non-human animals. However, a number of alternative explanations for success on
these tasks have yet to be ruled out. One hypothesis is that subjects may
respond to perceptual-motor feedback: repeating those actions that bring the
reward incrementally closer. Here, we devised a novel, forced-choice version of
the Aesop’s Fable task to assess whether subjects can solve water displacement
tasks when visual feedback is removed. Subjects
had to select only one set of objects, or one type of tube, into which all
objects were dropped at once, and the effect the
objects had on the water level was visually concealed. In the current
experiment, fifty-five 5-9 year old children were tested in six different
conditions in which we either varied object properties (floating vs. sinking,
hollow vs. solid, large vs. small and too large vs. small objects), the water
level (high vs. low) and/or the tube size (narrow vs. wide). We found that
children aged 8-9 years old were able to solve most of the water displacement
tasks on their first trial, without any opportunity for feedback, suggesting
that they mentally simulated the results of their actions before making a
choice. Children aged 5-7 years solved two conditions on their first trial (large
vs. small objects and high- vs. low-water levels), and learnt to solve most of
the remaining conditions over five trials. The developmental pattern shown here
is comparable to previous studies using the standard Aesop’s Fable task, where
8 year olds are typically successful from their first trial and 5-7 year olds
learn to pass over five trials. Thus, our results indicate that children do not
depend on visual feedback to solve these water displacement tasks. The forced-choice
paradigm we describe could be used comparatively to test whether non-human
animals require visual feedback to solve water displacement tasks.