How Social Psychology Shapes the Way We Measure Brand Trust
As part of a series on how psychology shapes the discipline of marketing research, I want to focus on something we are regularly asked to measure: trust. In marketing, we often focus on the message itself-is it clear, credible, believable? But social psychology points to something more fundamental. Trust often begins with the messenger.
Decades of research-including Source Credibility Theory developed by Carl Hovland and his colleagues-show that people evaluate information based on who is delivering it before they fully engage with the content itself. In practice, credibility is often established or lost before the message has a chance to do its work. People are not neutral processors of information. They interpret what they hear through the lens of who is speaking.
Who Is Saying It Matters as Much as What They Say
Trust is shaped by context, identity, and experience.
One of the most consistent findings in social psychology, including work grounded in Social Identity Theory, is that people are more likely to trust those they see as part of their in-group. This goes well beyond demographics. Our “tribes” reflect shared experiences, shared values, and a sense that the person speaking actually understands our world.
The same spokesperson can be highly trusted by one audience and far less trusted by another. Trust is not universal-it is contextual.
Credentials Open the Door. Trustworthiness Gets You In.
Social psychology draws an important distinction between expertise and trustworthiness. A healthcare professional brings expertise, signaling knowledge, training, and authority. Trustworthiness is something else. It is about whether people believe that person understands them and has their best interests in mind.
When someone feels that a system has not treated them fairly, they may not experience healthcare professionals as people who understand their situation. Expertise alone does not bridge that gap.
In those situations, people often turn to voices that feel more relatable-“someone like me”-because those voices reflect lived experience and practical understanding, not just credentials.
The Right Messenger Depends on the Job
Once you start looking at trust this way, it becomes much more actionable.
Healthcare professionals tend to be most effective when the goal is to explain something complex, reduce uncertainty, or establish credibility. Peers. or “someone like me,” are often more effective when the goal is to show how something works in real life, reduce hesitation, or make a behavior feel achievable. Community leaders and nonprofits may carry particular weight when trust is tied to local relevance or shared purpose.
In healthcare, for example, a doctor may be the most credible source to explain why a treatment works. But that explanation alone may not be enough to move someone to act. A patient story can make the message real by showing what the experience actually looks like day to day. One provides the explanation; the other provides proof in real life.
Persuasion Is a Team Sport
Agreeing with information is one thing. Reconsidering a belief or taking a new action is something very different.
When people are being asked to change their minds, a single messenger is often not enough. An expert can lay the groundwork for reconsideration by explaining why something is true. A peer can make that change feel possible by showing how it works in practice.
Pairing messengers addresses both sides of how people make decisions. The expert establishes credibility. The peer makes it real.
Past Experience Rewires How People Hear You
Experience plays a critical role in shaping how people respond to different messengers.
When someone has had positive, consistent experiences with a system, authority and expertise tend to reinforce trust. When experiences have been inconsistent or negative, people are more likely to question intent-and to rely more heavily on voices that feel relatable.
The COVID-19 pandemic is a clear example. Trust in public health officials eroded significantly for large segments of the population. Recommendations shifted as evidence evolved, which is how science works, but many people experienced those changes as inconsistency rather than rigor. Messaging came from multiple competing sources simultaneously, and the cumulative effect was confusion about who to believe. For some audiences, that erosion has not fully recovered.
In situations like this, pairing expert guidance with voices that feel more relatable or locally grounded can help bridge the gap between credibility and real-world relevance.
Measuring Trust Means Measuring Roles, Not Just Rankings
If trust is contextual, then identifying the right spokesperson requires more than a single question. Asking “Who do you trust most?” gives you a ranking, but it does not tell you how trust actually functions.
To make this actionable, research needs to separate the roles that different spokespeople play. Who do people trust to explain something clearly? Who do they trust to help them decide what to do? Who do they trust to understand their situation? These are not the same questions, and they often produce different answers.
Anchoring trust to real situations matters, too. Someone may trust a healthcare professional to explain a condition but turn to “someone like me” when deciding whether they can realistically act on that advice. And when it comes to changing minds, the distinction becomes even more important: who would someone listen to if they had to reconsider their current view? Who would make them feel comfortable changing their mind?
These questions begin to surface not just trust, but influence. The goal is not to identify a single “most trusted” spokesperson. It is to understand how different voices work together-because in most cases, the most effective approach combines both.
The Takeaway
Trust is not built by refining a message in isolation. It is built by matching the right voice to the right moment for the right audience. Get the messenger wrong, and even the most credible, well-crafted message will not land. Get it right, and the message almost takes care of itself.
Kirsty Nunez is the President and Chief Research Strategist at Q2 Insights, a research and innovation consulting firm with international reach and offices in San Diego. She holds graduate degrees in psychology and biostatistics and has spent over 30 years in marketing research, applying behavioral science to real-world decision-making. Q2 Insights specializes in a range of research and predictive analytics solutions and actively uses AI to enhance the speed and quality of insights delivery, while continuing to rely on human expertise and experience. AI is applied only to respondent data.
