When is there a more-credible effect?

Hoorens and Bruckmüller (2015) reported that people are more likely to judge comparison statements to be true when the comparison is framed as \textit{A is more than B} than when it is framed as \textit{B is less than A}. Skylark (2021) recently provided further evidence for this \textit{more-credible effect}, but found that it did not emerge for all stimulus sets. In particular, there was very little effect of comparative when participants evaluated the truth of statements comparing the amount of land required to produce certain foodstuffs. The present report describes two further pre-registered studies that probe the generality of the more-credible effect. Study 1 used the same land-use comparisons as Skylark (2021) but increased the masses of the foodstuffs from 1 kilo to 1000 tons (the idea being that 'less than' framing might only reduce credibility when the compared quantities are large). A manipulation check found that the change in stated mass increased the subjective size of the items, but there was still little effect of comparative on judgments of truth: more-than statements were judged true about 3\% more often than less-than statements, and the effect was not reliably different from zero. Study 2 asked people to judge the truth of statements comparing the CO2 production of pairs of countries selected from the most polluting countries in the world. A modest, 'significant' more-credible effect emerged, with more-than framing boosting perceived truth by approximately 5\%. Exploratory cross-study comparison indicated that the more-credible effect did not meaningfully differ between the two studies. The factors that determine when, and how far, more-than framing boosts the credibility of comparative statements remains an important topic for inquiry.