Animals in areas with objects showed increased locomotion compared to animals in arenas without objects. These tests can also have objects in the area to promote exploratory behaviors. As the tests go on, the number of head dipping decreases because the animal has now gotten used to the arena. To observe neophilia and learning behavior, the test is typically done multiple times. Increased dose of anxiolytics leads to sedation. Another animal that has been injected with an anxiolytic agent is then placed in the apparatus and then observed. To examine anxiety a single animal is placed in the apparatus for five minutes where it is observed and then removed. The procedure of this experiment can be modified depending on the behavior being measured. On the other hand, if the animal doesn’t show these behaviors, then it is more anxious.
These three behaviors are exploratory and the more they occur, the less anxious the animal is.
If the animal moves into the central area it is as separate observation because the central area is the most threatening to animals. Locomotion is the animal moving to a different area with all four paws. Rearing is when the animal stands on its hind legs. Head dipping is commonly defined as when the animal puts his head into the hole until its ears are level with the floor or in modern devices when it breaks the infrared beam.
The three common activities are head dipping, rearing, and locomotion. Modern devices are now monitored by computer and have infrared beams. Over the years the HBT apparatus has become more complex. The floor of the area is covered with holes. The HBT apparatus is an area with walls around it to prevent escape. The OFT also doesn’t differentiate between locomotion and exploration. Exploratory behavior requires a choice to be made to explore, but since the OFT is just simply a brightly lit area, the animal doesn’t have a choice. The HBT was designed in the 1970s to mitigate the flaws of the open field test (OFT), another animal model that measures anxiety and exploratory behavior.