By administering an online experiment, this study examined how source and journalistic domains affect the perceived objectivity, message credibility, medium credibility, bias, and overall journalistic quality of news stories among an adult sample (N = 370) recruited using Amazon’s Mechanical Turk (MTurk) service. Within the framework of the cognitive authority theory, the study found auto-written news stories were rated as more objective, credible (both message and medium credibility), and less biased. However, significant difference was found between a combined assessment condition (news stories with source and author information) and a message only assessment condition (news stories without source and author information) in the ratings of objectivity and credibility, but not bias. Moreover, significant differences were found in the objectivity and credibility ratings of auto-written and human-written news stories in the journalistic domains of politics, finance and sports news stories. In auto-written news stories, sports news stories were rated more objective and credible, while financial news stories were rated as more biased. In human-written stories, financial news stories were rated as more objective and credible. However, political news stories were rated as more biased among human-written news stories, and in cases where auto-written and human-written stories were combined.