A new study published in The Journal of Neuroscience provides neural evidence regarding how environmental cues can bias human decision-making. The research demonstrates that stimuli associated with specific rewards can directly engage the brain’s premotor system to shape action selection, even before an opportunity to act arises. This finding suggests that external triggers in daily life, such as advertising or familiar branding, may influence behavior by pre-activating specific movement pathways in the brain.
“Neuroscience is advancing rapidly, yet decision making remains a domain with many open questions. Our interest stems from the need to understand how humans decide by integrating simple associative processes, such as stimulus-reward and action-reward learning, into coherent choices,” explained study author Luigi Albert Enrico Degni, a PhD student at the University of Bologna.
“While these learning processes are relatively well understood, how the brain combines them in real time is still fascinating and poorly explained. Building on recent work suggesting that decisions are strongly shaped by the environment, our study starts from the idea that the motor system, often viewed as an output of choice, may instead be an integral part of the decision-making process itself.”
Scientists have established that humans and animals typically make choices based on the value they assign to expected outcomes. However, learned associations between cues and rewards often exert a powerful, unconscious influence on these choices. This phenomenon is known as Pavlovian-to-instrumental transfer.
Pavlovian-to-instrumental transfer describes a situation where a stimulus previously paired with a reward prompts an action that earns that same reward. For example, hearing an ice cream truck music might trigger the action of reaching for a wallet. This process can be adaptive, promoting efficiency, but it can also become dysregulated in conditions like addiction.
There are two distinct forms of this transfer. General transfer occurs when a cue creates a non-specific state of excitement or motivation, causing an individual to work faster or harder for any reward. Specific transfer happens when a cue guides a choice toward the particular reward associated with that cue.
Prevailing scientific models assume that specific transfer relies on the brain retrieving detailed sensory information about the reward. Theories propose that this sensory recall subsequently triggers the motor plans necessary to obtain that specific reward. This implies a direct link between the motivational properties of a cue and the motor system.
Despite the acceptance of these theories, there has been a lack of objective physiological evidence in humans to confirm this mechanism. It remained unclear if reward-predictive cues actually reactivate specific instrumental actions in the brain’s motor cortex. The authors of the current study aimed to identify the neural signatures of this process.
They hypothesized that this reactivation would occur in the premotor system. To observe this, they focused on beta-band oscillations in the brain. These are electrical brain waves ranging from 12 to 30 Hz.
A decrease in the power of beta waves, known as desynchronization, is a well-documented marker of action selection and motor preparation. The researchers anticipated that if a cue triggered a specific action plan, they would see beta desynchronization in the hemisphere of the brain controlling that specific hand.
The study included 42 healthy adult participants. The sample consisted of 22 women and 20 men, with an average age of approximately 23 years. All participants had no history of neurological or psychiatric conditions.
The researchers utilized electroencephalography (EEG) to record brain activity. Participants wore a cap with electrodes that measured electrical signals from the scalp while they performed a computer-based task. The task was designed to simulate a slot machine interface.
The experiment progressed through several distinct phases. First, participants underwent a Pavlovian learning phase. They learned to associate four different colored squares with specific outcomes.
Three of the colors were paired with three distinct food snacks that the participant had previously rated as highly desirable. A fourth color was associated with no reward. This established the predictive value of the visual cues.
Next, the participants moved to an instrumental learning phase. During this stage, they learned to press a left button or a right button to earn rewards. Crucially, the left and right buttons earned two of the distinct snacks used in the previous phase.
This setup created a specific link between an action (pressing left or right) and a specific outcome (a particular snack). The third snack was never associated with a button press. This design allowed the researchers to test different types of transfer.
Finally, the participants entered the transfer phase. This was the critical testing period where the influence of the cues on action selection was measured. In each trial, one of the colored cues appeared on the screen for three seconds.
After this three-second delay, the two response buttons appeared. Participants were free to press either button. Importantly, this phase was conducted under nominal extinction. This means participants were told they were earning rewards, but the rewards were not displayed, preventing the immediate presence of food from affecting the results.
The three-second delay between the cue and the buttons was a key methodological feature. It allowed the researchers to separate the brain activity related to the decision process from the activity related to the actual movement. They examined the EEG data during this specific interval.
The behavioral results confirmed that the participants experienced both specific and general transfer. When a cue appeared that was associated with a specific snack, participants were significantly more likely to press the button that earned that same snack. This indicated specific transfer.
Additionally, participants reacted faster when they saw any cue associated with a reward compared to the cue associated with no reward. This general invigoration of behavior indicated general transfer. These findings validated that the experimental setup successfully induced the desired psychological effects.
The neural findings provided the core evidence for the study’s hypothesis. The EEG data revealed a distinct pattern of brain activity during the specific transfer trials. When a participant viewed a cue linked to a specific action, beta power decreased significantly.
This decrease was lateralized. The brain controls movement on the opposite side of the body. The researchers observed that beta power dropped more in the hemisphere contralateral to the hand associated with the reward. For example, if a cue predicted a snack earned by the right hand, beta power dropped in the left hemisphere.
This lateralized desynchronization began shortly after the cue appeared. It was maintained throughout the three-second waiting period before the buttons were even visible. This suggests the brain was selecting and preparing the specific motor response based solely on the visual cue.
In contrast, cues that promoted general transfer did not elicit this lateralized pattern. The cue associated with the third snack, which required no specific action, increased arousal but did not trigger the specific motor preparation signals. The neutral control cue also failed to produce this effect.
The analysis showed that this neural signature was specific to the beta frequency band. Alpha and theta frequencies did not show the same lateralized modulation during the specific transfer trials. This reinforces the link between beta waves and motor decision-making.
“One surprising aspect of our study was how pronounced the effect of reward-predictive cues was on motor system activity,” Degni told PsyPost. “Using electroencephalography, we measured beta oscillations, a type of brain rhythm linked to action preparation, and found that these subtle signals were strongly modulated by environmental cues. This highlights how sensitive the motor system is to predictive stimuli, showing that even fine-grained neural signals can be powerfully influenced by the environment in which decisions are made.”
These results provide the first neural evidence in humans favoring the theory that Pavlovian cues reactivate instrumental actions. The study corroborates the existence of two dissociable neural pathways. One pathway mediates specific transfer through the premotor system.
The other pathway appears to influence performance through general motivational arousal. This general pathway functions independently of the premotor activity seen in specific transfer. The separation of these mechanisms advances the understanding of how associative learning drives behavior.
“Many people have experienced starting to reach for a product in a supermarket as soon as they encounter a familiar cue associated with it, such as a song used in advertising, without fully evaluating alternative options,” Degni said. “Our study provides a neural explanation for this effect, showing that reward-predictive stimuli can directly engage the motor system and bias action selection toward specific rewards. In this way, the environment can shape behaviour by influencing how actions are selected, not just what we choose.”
As with all research, there are some limitations. The analysis focused only on trials where participants made the “congruent” choice, selecting the hand matching the cue. The researchers did not analyze trials where participants resisted the cue and chose the opposite hand.
The exclusion of these incongruent trials was necessary due to the low number of such responses. As a result, the study does not explain the neural mechanisms involved in overriding these automatic biases. It remains unknown if the same beta desynchronization occurs when a person ultimately decides to act against the cue.
The experimental setting was also highly controlled. “A potential caveat is that our experiments took place in a laboratory, which is simpler and more controlled than real-world settings,” Degni said. “At the same time, this could also highlight the potential impact of these effects outside the lab, where people are constantly exposed to cues that can influence the motor system and decision-making. If the effect is already strong in a controlled environment, it may be even more pronounced in the complex contexts of everyday life.”
Future research could investigate the mechanisms of resistance to these cues. Understanding how the brain overrides Pavlovian influences is important for studying self-control. The authors also suggest exploring how these processes might become maladaptive.
“Our research is part of a broader international project examining the role of the motor system in cue-guided decisions, with converging results from other imaging techniques, such as fMRI,” Degni explained. “Looking ahead, we plan to study maladaptive processes, focusing on situations where cues might steer decisions in unhelpful directions, interfering with motor system activity rather than facilitating it.”
“For a long time, decision-making was seen as a purely sequential, economic process in which each potential outcome has a value and we simply choose the best one. This perspective is limited, because many factors can bias our choices, sometimes helping us and sometimes leading to suboptimal decisions, often as a way to reduce cognitive load. The motor system may play an active role in this process, shaping which actions are more likely to be taken in a given context.”
“We hope that this emerging view, which treats decision-making as part of a complex and intertwined brain process rather than a linear computation, will continue to gain traction and inspire further research,” the researcher continued. “Our brain is highly intricate and non-sequential, and understanding how decisions arise from this complexity remains one of the most exciting challenges in neuroscience.”
The study, “Cortical Beta Power Reflects the Influence of Pavlovian Cues on Human Decision-Making,” was authored by Gianluca Finotti, Luigi A. E. Degni, Marco Badioli, Daniela Dalbagno, Francesca Starita, Lara Bardi, Yulong Huang, Junjie Wei, Angela Sirigu, Valeria Gazzola, Giuseppe di Pellegrino and Sara Garofalo.
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