Hamburg - Next time you kiss your car when it starts on a cold day, or you curse your computer when it crashes - you may be relieved to know that it is only human nature to regard inanimate objects as sentient beings like yourself.

Scientists in Germany say our minds are hard-wired to interact with other human beings to such a degree that our minds just work better when we subconsciously think of objects in our environment as having human minds of their own.

To study how people perceive humanoid machines and attribute mental qualities to them, a team led by Soeren Krach from the RWTH Aachen University, in Germany, in cooperation with the Department of "Social Robotics" (Bielefeld University) and the Neuroimage Nord (Hamburg), observed the brain activity of a group of 20 subjects while they played a computer game against increasingly human-like machines - a regular computer notebook, a Lego-robot and a humanoid robot - and finally, against another person.

The results showed that neural activity in two areas of the brain related to mental attribution increased in parallel to how closely the gaming partner resembled a person.

The subjects also reported they enjoyed the game most when their opponent looked most like humans - and they thought those gaming partners were the most intelligent, too.

The results clearly demonstrated that neural activity in the medial prefrontal cortex as well as in the right temporo-parietal junction linearly increased with the degree of "human-likeness" of interaction partners.

In other words, the more the respective game partners exhibited human-like features, the more the participants engaged cortical regions associated with mental state attribution/mentalizing.

Further, in a debriefing questionnaire, participants stated having enjoyed the interactions most when their respective interaction partners displayed the most human features and accordingly evaluated their opponents as being more intelligent.

This study is the first ever to investigate the neuronal basics of direct human-robot interaction on a higher cognitive level such as mentalizing.

The findings, reported in the journal Public Library of Science, quoted the researchers as saying they expect the results of the study to impact long-lasting psychological and philosophical debates regarding human-machine interactions and especially the question of what causes humans to be perceived as human. (dpa)