Open Field Test (OFT) is a simple apparatus used in the assessment of locomotion, exploration, and anxiety. The open field task explores the innate responses of the subject to open spaces apart from their explorative drive. Thigmotaxis is often seen in animals such as rats and mice. This behavior of avoiding brightly lit open spaces is believed to be an evolutionary adaptive behavior that can be observed in many species. The Open-Field test exploits this fear in species to evaluate the different aspects of anxiety-related behaviors. Animals with a decreased level of anxiety are more likely to explore the central area of the open arena than animals with high levels of anxiety. Animals with high levels of anxiety will display reduced locomotion and exploration, with a preference to stay close to the walls of the open field arena. However, despite the fear, animals have also been known to explore threatening stimulus as part of their exploratory drive.
The apparatus was developed in the early 1930s by Calvin S. Hall to observe rat behavior in an open arena (Hall & Ballechey 1932). Hall and Ballachey’s experiment used a square arena that was marked into a grid. The experiment involved the observation of the rats to food stimulus placed within a barrier in the center of the arena. This experiment allowed observation of the influence of a positive stimulus on thigmotaxic behaviors of the rats and their emotionality. Though the apparatus is useful in the assessment of anxiety and explorative behaviors, it is debated that the task does not provide a specific measure of anxiety. To overcome these shortcomings, the 3-D Open Field apparatus can be used to allow a more precise measure of anxiety and fear-related behaviors.
The Open Field Test is usually used alongside other mazes that measure anxiety, such as the Elevated Plus Maze, Elevated Zero Maze, and Elevated Y-Maze(see also T-Maze), following anxiolytic and anxiogenic drug treatments. The Ziggurat task is a variation of the Open Field apparatus that uses ziggurats in the open space to create a complex environment. Another task that uses a similar apparatus to the Open-Field task is the Novel Object Recognition task used to evaluate the subject’s responses to novel objects.
The Open Field apparatus has a simple construct. Usually, a square arena that is surrounded by high walls to prevent escaping is used, though circular areas are also used. These walls can be transparent to allow the subject to view any visual stimuli placed around or can be opaque to limit observation to behaviors in response to brightly lit open spaces. The floors are often marked with square grid crossings, and the center of the arena is marked with a square. In addition, the apparatus can have additions and modifications to test different behaviors and responses.
- Open field test was developed by C. S. Hall in the early 1930s.
- Open Field task is used in the assessment of locomotion, exploratory and anxiety-related
- Open field task explores the innate thigmotaxic responses and exploratory drive.
- Hall’s used the rate of defecation and urination as a measure of emotionality.
- Open field test is a simple and easily modifiable apparatus with a wide range of research applications including aging, drug effects, and lesions.
- Open field task may not provide a specific measure of anxiety. Hence, it should be used in conjunction with other behavioral batteries.
- Open field task may also not satisfactorily differentiate anxiety from fear.