Output from different explanation methods on the input: A 'German shepherd dog' that is occluded by paper
Output from different explanation methods on the input: A 'Dalmatian' that is occluded by a baby
Pixel importance from high to low by CET for explaining 'bus', with partial occlusion
Pixel importance from high to low by DeepCover for explaining 'bus', with partial occlusion
Anomaly Input Images:
'airship'
'malinois'
'flamingo'
'bobsled'
DeepCover Output:
CET Output
We plant occlusions (aka “photobombers”) into ImageNet images and we record these occlusion pixels so that we can measure the intersection of explanations with the occluded pixels. Examples (and the corresponding CET explanations) from the Photo Bombing dadaset are as follows.
The occlusions planted in the photo bombing images can be regarded as the groundtruth for the explanation not to overlap with. Thanks to this, we run experiments with different tools and confirm that the intersection between the occlusion and CET is the smallest among all eight tools evaluated. This is complemented by the explanation size measured (aka the portion of pixels of the original input image for restoring the original decision), which shows that the explanation size from CET is also consistently smaller than other tools. The results from other explanation tools are a bix mixing (please see below).
To use the Photo Bombing Data: download link
While CET targets explaining partially occluded images, it also maintains a high performance for normal images (without occlusions) explanations. We tested this by using the ``roaming panda'' data set from DeepCover, a set of ImageNet images with explanation groundtruth, and we recorded the percentage (the number in the parenthesis ) of groundtruth explanations that were successfully detected by each tool: RAP (91.0%) > DeepCover (76.7%) > CET (72.3%) > Extremal (70.7%) > RISE (55.8%) > LRP (53.8%) > GBP (20.8%) > IG (12.2%). In contrast to the explanations for partial-occlusion images, RAP delivers the best performance on the ``roaming panda'' data set. However, CET's results are still better than those by most other tools. We observe that with or without occlusion does impact the performance of explanation tools, and CET achieves an overall better performance than other tools that are validated using complementary metrics in the evaluation.
CET explanations on the `roaming panda', using VGG16 and MobileNet