Strategies in landmark use by orangutans and human children.

Landmark use has been demonstrated in a variety of organisms, yet the manner in which landmarks are encoded and subsequently used appears to vary between and sometimes within species, even when faced with identical landmark arrays. In the present experiments, orangutans and human children were shown a square array of identical landmarks and were trained to locate a hidden goal in the centre of the array. In Experiments 1 and 2, the search space appeared to be discrete, with white gridlines dividing up the space, and in Experiments 3a and 3b, the search space was uniformly coloured, making it appear continuous. In all experiments, following training, subjects were given a single expansion test, to determine their landmark strategy use, based on peak search activity. The orangutans appeared to use absolute directional vectors from individual landmarks, with peak search activities on the inner corners of the square array, and they used this strategy persistently. In contrast, human children showed two landmark-based strategies, absolute directional vectors and a relational or "middle" strategy, with the majority of children starting their search in the middle region. Although some children, especially young children, persistently used one strategy like the orangutans, many changed strategies when the original one failed to yield the hidden goal.