Honeybees drink nectar from flowers. This, on first sight, seems a simple task: find flower, drink nectar, and return to nest. In reality the task is more complicated. Each flower species has different amounts of nectar, and they bloom at different times of day. To make the most of a foraging trip,honeybees need to make a series of complex decisions. Shaowu Zhang and his German colleague Juergen Tautz have demonstrated for the first time that honeybees can make two choices simultaneously, which greatly improves their chances of foraging successfully(p. 4420).
But before Zhang could begin offering the insects interesting choices, he taught them to perform a simple decision-making operation. Training the insects to follow a defined path through a maze to the feeder and allowing them to return to their hive through a specific entrance, both entrances having been marked with a distinctive visual cue, Zhang tested to see if bees would choose cues they had been trained to recognise when they were offered a variety of routes to both the maze and hive. They did. Having established the basic technique, Zhang set about using different factors to influence the insects' decisions about which routes to take.
First the team decided to test whether the bees could make decisions based on the time of day that they were foraging. By rewarding the bees with access to food and the hive, Zhang trained the bees to recognise one pattern in the morning, with another pattern used in the afternoon. When the bees were tested by offering them the choice of both patterns throughout the day, the honeybees clearly preferred the pattern they had been trained to recognise early in the day when tested in the morning and switched to the other pattern in the afternoon, demonstrating that they chose according to the time of day.
In their second test, the honeybees had to choose between visual cues depending on whether they had learned to recognise the cue when they were foraging or returning to the hive. Zhang marked the path to the feeder with a yellow cue so the honeybees associated this colour with foraging, while the unrewarded maze entrance was marked with a blue cue. At the hive these colours were reversed, so the open entrance had a blue cue to signify a return trip. When tested the honeybees continued to choose the cues they associated with rewards, showing that they made one choice to get to the feeder, but the opposite choice to get to the hive.
Neither of these results were a surprise to Zhang and his colleagues, who have studied honeybee cognition for many years. But both tests were designed to lead up to something far more complicated: whether honeybees can make two decisions simultaneously. In this case, can they choose cues depending on whether they were foraging or heading for the hive, as well as making those choices according to the time of day? This time access to the feeder was marked in the morning with one pattern that the insects should associate with foraging at the maze, and a different pattern at the hive entrance associated with homing. In the afternoon, these patterns swapped over. Impressively,during the test when the honeybees were offered a variety of routes through maze and home, the honeybees continued to choose the patterns that led to rewards during training, and definitely switched their preference between morning and afternoon. `We're seeing a time schedule', explains Zhang,`honeybees plan their activities in time and space'.
Honeybees may be small, but these results could have a big impact.`Honeybees perform many cognitive tasks similar to bigger animals and humans',says Zhang. This makes the simpler honeybee brain a good model for cognitive processes in general. Understanding this model may have implications for technology too. Robots can see, hear and touch, but making decisions based on these sensations is far more difficult to engineer. The next generation of robots may learn a lot from the simple honeybee.
