New research may explain why we sometimes overvalue items we've acquired—to an irrational degree—irrespective of their market or sentimental value. This phenomenon is called the endowment effect, and researchers have long puzzled over why it occurs, and why the size of the effect can vary so much across items when it does. It's important to understand, however, because the endowment effect can lead us to make unpredictable economic decisions, and it has far-reaching implications […]

In many social species, including humans, even if large group sizes provide competitive advantages over smaller neighboring groups, the preponderant role of adult males in territoriality has often been put forward, most likely biased by an anthropocentric perspective.

Few species develop as slowly as humans, both in terms of developing adult skills and brain development. Human infants are born so underdeveloped that they cannot survive without adult care and feeding for some years after birth. Children still need to learn fundamental skills such as walking, eating, talking, using tools and much more. The timing of these developmental milestones is used by doctors to determine if a child and the child's brain are developing normally. However, we know little […]

If someone around you yawns, the chances are that you too will soon yawn. In orangutans it has now been found that scratching is very contagious. This is what cognitive psychologists from Leiden discovered at Apenheul Primate Park. Publication in American Journal of Primatology.

One of the most promising theories for the evolution of human speech has finally received support from chimpanzee communication, in a study conducted by a group of researchers led by the University of Warwick.