Fig 1.
Examples of extrinsic and intrinsic bivariate encoding of geographic variables.
EN1: extrinsic (separable) encoding of variables according to size and color lightness; EN2: mental representation of extrinsic visualization (all the possibilities); IN: intrinsic (inseparable) encoding of variables according to hue and lightness.
Fig 2.
Examples of extrinsic visualization (left) and intrinsic visualization (right) used in the study. Legends for both extrinsic and intrinsic visualization are also given. Areas with identical values are depicted with two different encoding systems to enable a visual comparison of the differences between each visualization.
Fig 3.
Example of an intrinsic visualization item (subtest A–part A.1.).
The task was to select the area which contained “medium soil depth”; the correct answer was area No. 1.
Fig 4.
Example of an extrinsic visualization item (subtest B—part B.2).
The task was to select the area which best satisfied the conditions of “low soil depth” and “medium soil moisture”; the correct answer was area No. 3.
Fig 5.
Between-subject experimental design (subtests A and B; parts A.1, A.2, B.1 and B.2).
Both independent experimental groups, Intrinsic and Extrinsic, performed the test in exactly the same manner. The order of all items was constant for both groups, and all participants.
Fig 6.
Response correctness for the entire test.
Correctness was calculated as a ratio of the number of correct answers to the number of all answers.
Fig 7.
INT–red/yellow, EXT–blue. Particular attention was given to items with a significant difference between the two visualizations (1, 2, 9, 21, 28). The error rate was calculated as a percentage of incorrect answers of all answers.
Fig 8.
Mean response time per extrinsic/intrinsic visualizations (calculated from the response times to all extrinsic/intrinsic items for all participants).
Table 1.
Response times for the individual subtest parts (ms).
Fig 9.
Mean response time (ms) per item (calculated for the individual subtest levels).
Fig 10.
Mean response times (ms) per individual items for extrinsic and intrinsic visualization (all items).
Table 2.
Summary of AOI dwell times (ms).
Fig 11.
Mean AOI dwell time per extrinsic/intrinsic group (ms).
Fig 12.
Dwell time on AOI (%) for the extrinsic visualization (top) and intrinsic visualization (bottom). Extrinsic visualization–proportion of dwell time at AOI in single items; (top); Intrinsic visualization–proportion of dwell time at AOI in single items (bottom).
Fig 13.
Ratio of the direct map-to-legend/legend-to-map saccades to the total number of direct saccades (%) between the defined AOI (instructions, legend, map, button bar).