Electronic Supplementary Material (Whiten et al.)
2. ‘Honey dip’ Child Study
Method
Participants
Twelve 3- and 4-year-old children (range 36-55 months), four boys and eight girls
(Table 1, main paper), were recruited from a nursery school in Central Scotland.
Materials
Participants were presented with the ‘honey-dip’ box used by Marshall-Pescini and
Whiten (2008), modified for use with children (see techniques below), together with a
tool which could be used to perform either a ‘dipping’ technique or a more complex
‘probe-and-lever’ technique yielding more rewards (Fig. 6). The box was 9 x 6 x 6 cm
in size, was completely opaque, and was fixed to a wooden table at a height suitable for
young children to work on it.
Techniques applied
Participants witnessed two techniques applied to the box, simulating those used in the
Marshall-Pescini and Whiten study.
a) Dipping-technique. In the chimpanzee study this involved dipping a stick-tool into
honey inside the box. This was not hygienic for child subjects. Instead, the box was
filled with numerous coloured metallic stars and bracelet beads. To demonstrate dipping
for stars, echoing honey-dipping for the chimpanzees, the adult model used the index
finger of her left hand to slide open a small trapdoor (1 cm square) on top of the box.
Whilst holding this trap door open, the model used her right hand to insert a magnetic
stick-tool into the hole. Some stars would stick to this, so the tool could be withdrawn
and the stars easily pulled off it. The beads could not be removed in this way because
they were not metallic.
b) Probe-and-lever-technique. In the chimpanzee study, this involved inserting the
stick-tool into a hole on the side of the box, thus pushing in a rod holding the box lid
down. The stick could then be inserted in the top hole and the whole lid levered open so
that the entire contents of honey and nuts could be obtained. Pilot work confirmed this
was too easy for 3-4 year-old children to discover by themselves, so an additional,
spring-loaded sliding panel was added, covering the hole on the side of the box (Fig. 6).
In the present study, the model used the index finger of her left hand in order to
slide open the sprung panel on the side of the box. Whilst holding this open, the model
pushed the stick-tool into the hole thus revealed. This pushed in a small bolt that was
holding the lid of the box closed. After having poked the bolt, the model released the
sprung panel, allowing it to cover the bolt once more. The model then employed a
variation of the dipping technique, opening the trap door, inserting the tool, and using it
as a lever to open the hinged lid, making all of the box contents available. The
incorporation of the dipping technique variation into this procedure, meant that the latter
was built cumulatively on the already mastered dipping technique.
As in the chimpanzee study this more complex technique allowed all the
contents of the box to be obtained, including larger bracelet charms evidently highly
attractive to the children. The dipping technique did not allow the participants to obtain
these larger non-metallic rewards. Many insertions were required to obtain all the stars.
In contrast the probing technique allowed rapid access to all the stars and charms.
Procedure
The procedure began with a no-model baseline phase, followed by two experimental
phases. These involved first the dipping technique, and then if this was mastered by the
child, a second phase in which the probe-and-lever technique was modeled.
Baseline phase
In the baseline phase each participant was allowed to explore the box individually.
Upon entering the testing room participants were seated in front of the box and asked
‘What do you think you do with this?’ The child was then allowed to interact with the
box for two minutes, or earlier if they indicated they did not wish to continue. One
participant discovered the dipping technique individually in this phase, and was
accordingly progressed to Experimental phase 2, described further below.
Experimental phase 1: The dipping technique
This experimental phase began on completion of the baseline phase. The experimenter
sat to one side of the child and presented four consecutive task demonstrations of the
dipping technique, removing the stars from the tool after each withdrawal. After four
task demonstrations the experimenter said ‘Now it’s your turn’ Each child was allowed
up to three dips. The number of stars retrieved was counted and traded for an equal
number of child-friendly small beads that the children could place on a bracelet string.
Experimental phase 2: The probing technique
Upon completion of the dipping phase, which was successfully achieved by all
participants, they were exposed to four consecutive demonstrations of the probe-andlever technique. The experimenter again said ‘Now it’s your turn’ If the child was
successful in opening the box they were allowed to choose one large bracelet charm to
place on their bracelet string.
Statistical Analyses
As noted above, all children successfully dipped in Phase 1. There was thus significant
evidence for social learning in this phase, since only one child was successful in the
baseline phase (McNemar Test, p < 0.006).
In Phase 2, eight children successfully mastered the more complex technique, three
completed part of it by pushing back the sliding panel but failed to insert the stick-tool
to push the bolt (Table 1) and just one child persisted in using only the dipping
technique, as all chimpanzees had done in the earlier study. Significantly more of the
children thus showed evidence of cumulative social learning than had the chimpanzees
(Fisher Test, p < 0.03).