The capacity for abstract thinking does not belong to humans alone, as studies of other vertebrates, such as primates, pigeons and dolphins, have shown. Now new research indicates that invertebrates, too, possess higher cognitive functions. According to a report in the current issue of the journal Nature, the humble honeybee can form "sameness" and "difference" concepts¿an ability that may help them in their daily foraging activities.

To probe the honeybee's mental prowess, Martin Giurfa of the Free University of Berlin in Germany and his colleagues first trained the insects to associate certain stimuli with a reward: sugar. For example, in one experiment bees saw the color blue at the entrance to a so-called Y-maze. The entrance led to a decision chamber, where the bees could choose between two paths: one carried a blue target, the other carried yellow. The bees received a reward only if they chose blue, the same color as that seen at the entrance.

The team then tested whether the bees could apply what they had learned to a new situation. Blue and yellow patches were replaced with black and white patterns of vertical and horizontal bars. The bees passed with flying colors, heading straight for the pattern that matched what they saw at the entrance. Moreover, other experiments revealed that the insects could even transfer their knowledge across the senses: bees that learned about sameness through olfactory training were able to apply that concept to situations involving visual stimuli.

These results, the authors conclude, demonstrate that "higher cognitive functions are not a privilege of the vertebrates." Moreover, because the honeybee nervous system is relatively simple, they write, "there is a realistic chance of uncovering the neural mechanisms that underlie this capacity."