# Evaluation of Effective Cognition for the QGIS Processing Modeler
## 4 Evaluation of Processing Modeler
### Evaluation by Eye-Tracking Measurements
In these models, the response time was longer than the previously presented models and tasks. The average time of fixation was also longer. It verifies the necessity of reading labels by users. The solution of semantic transparency by text label consume more time for comprehension. The longer times confirms the hypothesis H2 about negative influences of insufficiencies to effective comprehension. Both of the experiments mentioned above (about source library and the comparison of the data type of input and output data) verified that Semantic Transparency was low in the Processing Modeler. The results about the number of correct and incorrect answers in all tasks presented in this section report that some insufficiencies adversely affect the cognition as it is stated in hypothesis H1. From eye-tracking testing, we received not only cross-validation of results by Physics of Notations but other new information. The interesting information was finding the reading patterns and influence of flow orientation to the respondent reading directions. To find the reading pattern of users, gazes were aggregated. A comparison of the same diagram from the free viewing section and a section  
Figure 16: The model with different source libraries of operations in a diagonal arrangement. Figure 15: Attention heat map for the task to find the ‘Fixed Distance Buffer’ operation. with tasks is given in Figure 17. Aggregations in both cases revealed that the orientation of data flow expressed by connector lines had a significant influence. Reading began in the middle of the stimulus according to the middle fixation cross in the previous stimulus. Gazes were attracted to the upper left corner and continued horizontally to the right. People's habits of reading lines of text were very strong, especially in free viewing (Figure 17a). The lower part of Figure 17b also depicts strongly followed lines. Only a small number of gazes skips between two main horizontal workflow lines. Free viewing was not as systematic as task-oriented gaze aggregations. Two models tested the effect of _symbol alignment in the model_. This finding can be linked to the principle of _Cognitive Interaction_. The first model had aligned symbols; the second model had no aligned symbols. The functionality was the same. The question was the same for both models: _\"How many functions are in the model?\"_ (task A8, A9). It was enough to count only the white rectangles in large models. The number of the expected correct answers was eight. The first aligned model recorded two incorrect answers and the second recorded seven. The average task time was much shorter in the first tasks. The non-parametrical Kruskal-Wallis test was used for eye-tracking metrics due to non-parametrical distribution of measured values. It tested if medians of groups are equal means they have the same distribution [35]. The significance level for all Kruskal-Wallis tests was set to p-value 0.05. The test was run three times for several fixations, scanpath lengths and number of fixations per second. The test compared tree measured values for the aligned and non-aligned model (A8 and A9). Kruskal-Wallis test found statistically significant differences for all metrics: the number of fixations, scanpath lengths, and number of fixations per second. The model where the symbols were unaligned showed much worse values for all metrics (task A9). Therefore, aligning the symbols in the model made it easier to read and understand the model. This eye-tracking evaluation supports the recommendation for the new function of the automatic alignment of symbols in this graphical editor. Figure 17: Aggregate directions of scanpaths of respondents in the model during free-oriented reading (**a**) and task-oriented reading (**b**). Three groups of models with the same functionality were prepared to test _the orientation of flow_ and find if any orientation is better for users. The models in each group differed only by orientation. Three orientations were tested: vertical, horizontal, and diagonal.