Measures
Inactivity and floating
A floating mouse isn't searching. Measure it so you know.
Rats, said the original notes, "don't have the option to float". Mice do. Dr Roger Morris noticed that in probe trials many mice head for the side where they'll be lifted out, "where some float". Measuring inactivity helps you see whether a poor score is about memory or about giving up.
Why it matters
Floating time tells you whether a subject stopped moving, which helps explain slow or unusual results.
More detail
Inactivity is the percentage of trial time below a speed threshold, default 0.05 m/s (5 cm/s), and it is contextual: it helps interpret latency, path length and crossings. Poor spatial scores with low float time suggest genuine cognitive impairment; poor scores with high float time may point to motivation, mood or sensorimotor issues.
HVS Image smooths positions sampled at up to 60 Hz to one position per 100 ms and classes intervals below threshold as inactive (Inactivity technical note, doi:10.5281/zenodo.21797205). The measure is threshold-dependent and cannot separate causes without supporting evidence; rodent and human VR values should not be compared directly.
Inactivity or floating
Inactivity is the percentage of trial time spent moving below a speed threshold. High inactivity has several possible causes, so read it alongside latency, path length, crossings and Gallagher proximity.
More detail
The default threshold is 0.05 m/s (5 cm/s), which can be changed for the species, protocol or virtual environment. Long latency with little inactivity suggests active but inefficient navigation; with substantial inactivity it may reflect engagement or motor factors rather than navigation alone.
Method (HVS Image): positions sampled at up to 60 Hz are smoothed to one position per 100 ms; intervals below threshold are inactive; % = summed inactive duration / total trial duration. High inactivity with good proximity suggests retained knowledge despite slow movement. Rodent and human VR values should not be compared directly.
Questions people ask
What is percentage time floating or inactive?
Percentage time inactive (floating in the water maze) is the share of the trial in which the subject moved slower than a set speed, 5 cm/s by default. It gives context for other results, such as a long latency, rather than measuring learning directly.
More detail
Inactivity (floating or slow swim in rodents; inactivity or slow movement in VR) is the percentage of trial time spent below a speed threshold, default 0.05 m/s (5 cm/s), which can be changed for the species, protocol or virtual environment. It is contextual: it helps interpret latency, path length and crossings.
Going deeper
Method (HVS Image): positions sampled at up to 60 Hz are smoothed to one position per 100 ms; speed per interval = Euclidean distance between successive smoothed positions / elapsed time; intervals below threshold are inactive; % = summed inactive duration / total trial duration. Rodent and human VR values should not be compared directly. Ref: doi:10.5281/zenodo.21797205.
How should I interpret high inactivity?
High inactivity means the subject spent a lot of the trial floating or moving very slowly. It can come from tiredness, stress, low motivation, a drug effect, a movement problem or poor memory, so it is not a learning score on its own. 1) Compare it with latency and path length. 2) Check crossings, close encounters and Gallagher proximity. 3) Good proximity with high inactivity suggests the subject still knows where the target is.
More detail
Inactivity is the percentage of trial time spent moving below a speed threshold (default 0.05 m/s), so high inactivity means the subject spent much of the trial floating, pausing or moving very slowly. It has several possible causes: lower engagement, strategic pausing, fatigue, stress or anxiety, drug effects, motor impairment, confusion or impaired spatial memory. It can lengthen escape latency and reduce probe-trial crossings. Long latency with little inactivity suggests active but inefficient navigation; with substantial inactivity it may reflect engagement or motor factors rather than navigation alone.
Going deeper
Read it alongside escape latency and path length, average and active speed, crossings and close encounters, time near the platform and Gallagher proximity, heading angle, path efficiency, the corridor test, time slices and behaviour identification. High inactivity with good proximity suggests retained knowledge despite slow movement. The value depends on the threshold, and it cannot separate causes without supporting evidence. Ref: doi:10.5281/zenodo.21797205.
For how floating is detected from a track, see floating or inactivity in Morris water maze analysis.
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