A study co-authored by Junior Professor Benedikt Ehinger from the Stuttgart Center for Simulation Science (SimTech) has revealed that certain neural signals previously thought to represent evidence accumulation during decision-making may, in fact, be artefacts. The research, titled "Common Neural Choice Signals Can Emerge Artefactually Amid Multiple Distinct Value Signals", and published in Nature Human Behaviour, challenges long-standing assumptions about the brain's role in value-based choices.
The study, led by Romy Frömer and including contributions from Benedikt Ehinger, Matthew R. Nassar, and Amitai Shenhav, used electroencephalography (EEG) to explore the neural processes behind decision-making.
The team set out to test whether neural signatures of decision-making can be temporally separated from other value-related neural signals that are independent of the choice process itself. Their analysis revealed that neural signals reflecting automatic, affective reactions to choose options, such as how much a person likes a set of options, emerge early in the decision process, locked to the moment the stimuli are presented. In contrast, signals related to choose difficulty appeared closer to the moment of deciding, but surprisingly, neither set of signals matched the expected profile for evidence accumulation - where the brain gradually gathers evidence in favor of one option until a choice is made.
One of the most significant findings of the study was that specific brain activity signatures, which many researchers had previously interpreted as neural evidence accumulation was, in fact, an artefact. This artefact arose due to overlap between neural signals that are locked to the presentation of stimuli and those locked to the response, particularly when choices are made quickly. By employing new analytical methods to separate these overlapping signals, the researchers were able to show that the previously observed "ramping" neural activity, often interpreted as evidence accumulation, disappeared once these artefacts were accounted for.
By re-analyzing data from four prior studies, and simulating a broad set of new conditions, the team further demonstrated that this phenomenon was not limited to their own experimental setup. Across both value-based and perceptual decision-making tasks, the researchers found that evidence accumulation signals vanished when properly controlling for the overlap between stimulus- and response-locked neural activity. This calls into question many previous interpretations of neural data in decision-making research.
Junior Professor Benedikt Ehinger, a key contributor to the study, emphasized the broader implications of the findings. "Our research highlights the complexity of interpreting neural data. What we believed were clear signatures of decision-making processes might, in fact, be more reflective of automatic responses to the options presented. This finding underscores the need for sophisticated methods in neuroscience to avoid such misinterpretations."
The study's findings are expected to significantly impact how future research approaches the neural correlates of decision-making. Understanding how the brain evaluates options and makes choices is not only crucial for neuroscience but also has broader applications in areas such as psychology, artificial intelligence, and even consumer behavior.
Title: Common Neural Choice Signals Can Emerge Artefactually Amid Multiple Distinct Value Signals
Authors: Romy Frömer, Benedikt Ehinger, Matthew R. Nassar, Amitai Shenhav
Published: 6 September 2024 in Nature Human Behaviour
DOI: https://doi.org/10.1038/s41562-024-01971-z