Department of Physics, Chemistry and Biology (IFM)

Lateral biases for single behaviors, both at the individual and at the population-level, have been reported in a variety of vertebrates, including fish, amphibians, reptiles, birds, and mammals. However, evidence for handedness at the population-level in nonhuman animals is inconclusive and thus the evolutionary origins of human handedness are still not entirely understood.

Although laterality has been studied in many species, most studies have focused on nonhuman primates because they are biologically close to humans and are known for their great dexterity. To date, most studies of lateralized behavior in nonhuman primates have focused on our closest relatives, the Great Apes. In contrast, only few studies have reported on lateralized behavior in the Lesser Apes, that is, the gibbons.

All studies on lateralized behavior in gibbons so far included only a limited number of animals or combined data of different species of gibbons. Furthermore, in all previous studies only one or, at best, a couple of different behaviors were included, which prevents any conclusions regarding consistency of hand use across motor patterns.

Therefore it was the aim of the present study:

• to assess lateralized behavior in 15 white-handed gibbons for a variety of motor patterns that are part of their natural behavioral repertoire.
• to assess lateralized behavior of the same animals in a manual tube task that is not part of their natural behavioral repertoire.
• to assess consistency of the preferred hand across tasks per individual.
• to compare the data on spontaneously occurring lateralized behavior to those in a task-related lateralized behavior (tube task).
• to assess whether the gibbons display hand preferences at the population-level.