Gaze Duration Statistics
The gaze duration statistics node computes some statistics regarding gazes on AOIs. Thus, it presupposes the existence of AOI data, or other enumerable columns.
Output
The output of the gaze duration statistics node are tables containing one row for each distinct value contained in the selected AOI column. The columns of the tables contain the following statistics:
- Total Gaze Duration
- How long was looked at the specific AOI in total.
- Normalized Gaze Duration
- A relative value of how long the specific AOI was looked at, normalized to 1.
- Average Gaze Duration
- How long was looked at the specific AOI in average.
- Maximum Gaze Duration
- The longest time someone looked at the specific AOI continuously.
- Minimum Gaze Duration
- The shortest time someone looked at the specific AOI continuously.
- Gaze Count
- How often was the specific AOI looked at.
- Time To First Fixation
- The time between the start of the data and the first time the participant looked at a specific AOI. Note that if you execute the gaze duration statistics on a marking, the time to first fixation is computed relative to the start of the marking.
Aggregation
The gaze duration statistics node allows aggregation. Depending on the selected aggregation, the output values will reflect the gaze duration statistics of not just one participant, but all selected participants and/or scenarios / data sets. In particular, the effects of aggregation are:
- Total Gaze Duration
- The sum of all aggregated total gaze durations.
- Normalized Gaze Duration
- The sum of all aggregated total gaze durations normalized via the sum of all aggregated gaze counts.
- Average Gaze Duration
- How long was looked at the specific AOI in average.
- Maximum Gaze Duration
- The longest time of all all aggregated maximum gaze durations.
- Minimum Gaze Duration
- The shortest time of all aggregated minimum gaze durations.
- Gaze Count
- The sum of all aggregated gaze counts.
- Time To First Fixation
- The shortest time of all aggregated time to first fixations.
Settings
- Time Column:
- The time column, used for the computation of durations. Only columns containing monotonically increasing numbers can be selected. Note that the resulting statistics are displayed in the same time unit as used in this column.
- AOI Column:
- The column for which the statistics are computed, i.e. normally the AOI column. Only enumerable columns can be selected.
- Used / Ignored Values:
Determines ignored values, and additionally the sequence of the used values in the output. Use drag & drop to change.
Note, that ignoring values does not simply remove them from the output as if the rows containing these values did not exist. Instead, if an ignored value exists between equal values, the computation assumes that the ignored value should be the same value as the value between which it exists. E.g. if a sequence AAXXAAA exists, and X is ignored, the computed statistics are equal to the sequence AAAAAAA. If an ignored value exists between two values that are different, the algorithm acts as if the ignored value does not exist, as it can not be decided to which of the two values the ignored value should belong. E.g. if a sequence AAXXBBB exists, and X is ignored, the computed statistics are equal to the sequence AABBB, except for the normalized gaze duration, as this uses the total length as reference, and thus sums to less than 1.0, if a value is ignored.
This behavior is intentional and can be used to correct small detection errors. It corresponds the ignore function in the Parallel Scan Path, and the result reflects what can be seen in this visualization, if the same value is ignored. If used excessively, ignoring values can lead to results that might create incorrect impressions. If in doubt, ignoring values should not be used.
- Output as TimeSpan:
- Decides whether computed times are output in a TimeSpan format (hh:mm:ss[.ffff]) or as a double. If Output as TimeSpan is enabled, the TimeToFirstFixation column is a string that looks like a TimeSpan. The reason is that a distinction between looking immediately at an AOI (time to first fixation = 0), and never looking at an AOI (time to first fixation = "[null]") is required. If you want to do further computations on the TimeToFirstFixation results, we recommend disabling Output as TimeSpan.
- Output Unit:
- The time unit that is used for the output, if Output as TimeSpan is false. Note that this can only result in the correct unit, if the unit of the Time Column is set in the source Data Node. If the Output Unit is set to "None", the result is output in the same unit as the Time Column.