That's right. The authors operationalized "highly aesthetic quality" and grounded it in composition, lighting, color and contrast, subject and background, and

That's right. The authors operationalized "highly aesthetic quality" and grounded it in composition, lighting, color and contrast, subject and background, and "additional subjective assessments." There's zero citations in this section related to accessing artistic quality, operationalization, or grounding. A LOT of programmers are going to hate this, but if you're doing soft-sciences work(which this is), you should be knowledgeable in that area and cite some sources that indicate you've at least considered what you're doing. The lack of citations in this area is an unknowing admittance of that ignorance. I don't care if they cite a paper just to disagree with it, but to not know that they don't know is simply unacceptable. This is basic undergrad material in other relevant fields.