HauN et al. (2014)

This study has two components. You should learn study one.

Aim(s)

To directly compare human and nonhuman tendencies to adjust their behaviour to that of their peers in a single, comparable scenario.

Specifically, to compare 2-year-old children’s, chimpanzees’, and orangutans’ tendencies to abandon an individually acquired behavioural strategy after being exposed to a majority of peers demonstrating an equally effective alternative strategy.

Procedure

Sample: sample of 18 children (Homo sapiens; 9 female, 9 male; mean age = 28 months), 12 chimpanzees (Pan troglodytes; 7 female, 5 male; mean age = 121 months), and 12 orangutans (Pongo pygmaeus; 6 female, 6 male; mean age = 102 months). The planned goal of 18 participants per species was not met because of a lack of available animals.

The experiment consisted of a box with three sections, each was a different colour. The sections were arranged horizontally; the two outer sections were the same height; the middle section was shorter. In the top of each section was a hole.

The box was attached to a steel mesh observation room in the case of the chimpanzees and orangutans, and it was placed on the ground for human children. When a ball was dropped in one of the holes, a reward was dispensed from the bottom of that box. The rewards were controlled. Rewards were highly desirable to participants, with peanuts for chimpanzees and orangutans, and chocolate drops for human children.

Initial phase

Participants learned that balls could be put in all boxes, but only one would give rewards. They dropped balls in the sections until they used the assigned coloured section (rewarding box) in 8 out of 10 consecutive trials. They were then taken approximately 2 meters from the box, and watched while three familiar nonspecific peers (demonstrators) interact with the box one after the other. All participants could observe the actions of the demonstrator and the dispensing of rewards.

The three demonstrators all used the same section, different from the participant’s preference, twice and received one reward in return for every ball. After the six demonstrations, the testing period began.

Testing phase

Participants were given three balls, one at a time, and could put each ball into whichever section they chose. All three of choices were rewarded. The choices were coded twice by two coders, as either; switch, switching to match the majority response stay, staying with the participant’s own preference other, neither the demonstrated nor the individually preferred one.

Results

To calculate tendencies to switch to match peers, the number of stay responses was subtracted from the number of switch responses, resulting in difference scores between −3 and +3. Negative scores indicated a preference to stay and positive scores indicated a preference to switch to peer group choice.