Measures
Escape latency: time to find the platform
The oldest water maze measure, and still the first one people look at.
Escape latency is simply how long the animal takes to reach the platform. In his 1999 probe-trial essay, Dr Roger Morris describes the time falling from an initial maximum (for example 90 seconds for the trial) to a base level where there is no significant improvement each day, generally around 10 to 25 seconds depending on the size of the pool and platform.
Why it matters
Latency is the time to reach the platform, a simple first sign of whether learning is happening.
More detail
In repeated hidden-platform trials, a consistent fall in latency indicates learning of the platform location. In cued (visible platform) trials, latency that does not improve could point to visual or sensorimotor impairments, lack of motivation or general cognitive issues, which is why cued trials are a useful control.
Latency does not reveal strategy, is affected by motor speed, start point and start-goal distance, and is subject to floor and ceiling effects, so it should not be used in isolation. Morris (1984) described developments of the hidden-platform water maze procedure. Read latency with path ratio, heading angle and Gallagher proximity.
Escape latency
Latency is the time to reach the platform, in seconds. Shorter is usually better, but it doesn't show strategy and is affected by speed and start distance, so read it with path ratio, heading and Gallagher measures.
More detail
HVS starts timing when you click as the subject enters, and ends it by platform detection, after a dwell time, or manually. Latency is useful in cued, hidden, reversal and probe phases, and the suffix sc means seconds.
Because latency is affected by speed, start distance and floor or ceiling effects, a fall in latency on its own does not prove spatial learning; check that average speed is similar between groups and look at path ratio and heading before drawing conclusions.
Questions people ask
What are the limitations of escape latency?
Escape latency is the time the subject takes to reach the platform. Latency doesn't show strategy and is affected by speed, start distance and floor or ceiling effects, so read it with path ratio, heading, Gallagher measures and behaviour identification. HVS starts timing when you click as the subject enters, and ends it by platform detection, after a dwell time, or manually.
More detail
Escape latency is the time from release until the subject reaches the platform. Its limitations: it does not show which strategy was used; it is affected by swimming speed and by how far the start is from the platform; and differences are compressed by a ceiling at the maximum trial time and by a floor in well-trained groups. HVS Image starts timing when you click as the subject enters and ends it by platform detection, after a dwell time, or manually. Linking the start to release and detecting arrival objectively avoids premature starts and subjective arrival times. Latency is useful in cued, hidden, reversal and probe phases. Read latency with path ratio, heading angle, Gallagher measures and behaviour identification.
Going deeper
Because latency mixes speed, strategy and motivation, two subjects with the same latency can have searched very differently: one swimming directly but slowly, another fast but circling. Ceiling effects at the maximum trial time and floor effects in well-trained groups both compress differences, so report path ratio and Gallagher measures alongside latency.
HVS Image has a page on latency in Morris water maze analysis.
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