swimming in the pool before reaching the platform. Over the years, many different versions of this test have been performed with a large amount of variables. For example, neuroscientists examine the effect of differences of sex, weight, strength, stress levels, age, and strain of species. The results vary dramatically, so researchers cannot draw conclusions unless these variables are kept constant. Many different size pools have been used throughout the history of this task, but it has been shown that this does not have a significant impact on the results of the test. In early versions of the task, researchers only timed latency to escape, however video tracking devices are now routinely used to measure the path to escape, time spent in each quadrant, and distance traveled in the pool. Original experiment In Morris' first experiment, the apparatus was a large circular pool, 1.30 m across and 0.60 m high. The purpose of the original experiment was to show that spatial learning does not require the presence of local cues, meaning that rats can learn to locate an object without any auditory, visual, or olfactory cues. Analysis The earliest measure of learning is escape latency, which is the time it takes to find the platform. However, this measure is confounded by swimming speed, not necessarily a cognitive factor, and path length between point of origin and platform is a parameter more closely related to spatial learning. Further parameters are the Gallagher measure, the average distance to the platform, and the Whishaw corridor test, which measures time and path in a strip directly leading from swim-start to platform. Other parameters are measured during probe trials: the escape platform is removed and the mice or rats are allowed to search for it for a fixed time (often 60 seconds). Variables measured are time and path length in quadrants, time near platform, and platform crossings. Comparison to maze tasks Like other spatial tasks, such as the T-maze and radial arm maze, the Morris water navigation task is supposed to measure spatial memory, movement control, and cognitive mapping. The T-maze and radial arm maze are much more structured in comparison. The T-maze, for instance, only requires the rat or mouse to make a binary decision, choose left or right (or East or West). In the Morris water navigation task, on the other hand, the animal needs to decide continually where to go. Another reason this