Humans use two separate processes to determine the subtle distinctions between true and false in their daily lives, according to a new report from team of Portuguese and Italian researchers from the Universities of Lisbon and Vita-Salute, Milan.
Writing about their neuroimaging study, titled 'June Cortex', the researchers point out that deciding whether a statement is true involves memory, and that determining whether one is false relies on reasoning and problem-solving processes.
Using a feature verification task and functional Magnetic Resonance Imaging (fMRI), the researchers examined the impact of true and false sentences on brain activity.
They asked the participants to read simple sentences composed of a concept-feature pair-like 'the plane lands'-and to decide whether the sentence was true or false.
The researcher revealed that true and false statements were equated in terms of ambiguity, and exactly the same concepts and features were used across the two types of sentences.
They observed that false statements differentially activated the right fronto-polar cortex in areas that have been previously related to reasoning tasks.
The activations related to true statements involved the left inferior parietal cortex and the caudate nucleus bilaterally. The former activation may be hypothesized to reflect continued thematic semantic analysis and a more extended memory search.
The caudate activation may also reflect this search and matching processes as well as the fact that recognizing a sentence as true is in itself a positive reward for the subject, as this area is also involved in processing reward-related information.
Considering the results from the present experiment and from previous studies, the researchers say that it seems that when the differences between truth and falsehoods are clear-cut, people behave like relativists, and use similar processes to arrive at a decision.
However, when differences are more subtle, people adhere to a categorical distinction and use qualitatively different processes to decide what is true from false.