From Nike to Google and Volkswagen, many leading brands have employed voice-over narration – in which information about a brand or product is conveyed by one or more off-screen voices – in television commercials and product launch videos. This practice has spilled over into the online realm as video platforms such as TikTok, YouTube and Instagram have spiked in popularity in the past few years.

However, despite the ubiquity of video marketing, there has been little research into the impact of the narrator voice on consumer persuasion. In our study, published in the Journal of Marketing Research, Hannah H. Chang, Anirban Mukherjee and I investigate whether the number of narrating voices in a video can play a role in helping companies capture the attention of consumers in today’s crowded and competitive marketplace.

Analysing Kickstarter videos

Video marketing typically visually depicts a featured product, with one or more off-screen narrators discussing its features and benefits. For instance, in Apple’s video introducing the AirPods Max, two narrators sequentially describe the product’s vast range of features. Another video by the brand that accompanied the launch of the MacBook Pro features a voice-over by just a single narrator.

Upon individuals’ initial exposure to such videos, does the number of narrating voices affect consumers’ attention and processing of the content and their subsequent behaviour? If so, is this effect disruptive or facilitative?

We examined these questions in a series of studies, including one that leveraged data composed of marketing videos found on the online crowdfunding platform Kickstarter – an important avenue to drive the adoption of new products. The platform is a self-contained marketplace, housing not only a comprehensive description of marketing communications messages directed at consumers but also a detailed account of consequential consumer behaviour.

On Kickstarter and other crowdfunding outlets, a video that features the product is among the first elements potential customers see on a project page, making it important for customer conversion. Indeed, prior studies note that the majority of Kickstarter projects (between 80 and 86 percent) include product videos.

Using machine learning, text mining and natural language processing, we analysed over 11,000 Kickstarter crowdfunding videos and more than 3.6 million customer transactions worth US$382 million in pledged funding.

Our results show that having more voices narrate a product message is associated with improved project outcomes. On average, the presence of an additional voice was associated with raising about US$12,795 more in project funding (a 39 percent increase), attaining the support of 118 more project backers (a 38 percent increase), and boosting the probability of funding success by 1.6 percent.

The voice numerosity effect

We suggest that during initial exposure to a marketing video, hearing different voices successively narrate a message can be more persuasive than when a single voice delivers that exact same message. When a new narrator’s voice carries on a persuasive message, the change in voice can help sustain consumers’ attention and their processing of the next piece of the spoken message, which might not be processed otherwise.

We call this phenomenon the voice numerosity effect. Prior studies have shown that a change in voice can involuntarily capture an individual’s attention, even if there are other visual or auditory tasks competing for their awareness. The human brain is naturally predisposed to attend to the human voice – babies can recognise this even before they understand language. It activates distinct regions in the brain, quickly draws attention and evokes immediate and greater processing.

However, certain factors can weaken this phenomenon. We found that the voice numerosity effect is mediated by consumers’ cognitive responses and bandwidth to process the content. Once a recipient’s attention is obtained, they must allocate processing resources for the attentional advantage to translate into greater persuasive impact.

Based on our findings, we suggest that the voice numerosity effect is more prominent when consumers have greater opportunity and ability to process the message, and weaker when competing factors prevent this from occurring. Examples include the narrator speaking too quickly or if the recipient must contend with other distractions.

Implications for video marketing

Our research has clear strategic potential and significant economic implications in today’s crowded marketing ecosystem, where video reigns supreme. Current industry practice prizes a clear speaking voice that conveys both authority and relatability. However, it has yet to consider how the number of narrating voices can boost the success of video-based marketing initiatives.

We recommend that entrepreneurs, marketing practitioners and product managers consider the number and type of voice-overs when designing communications. Beyond the realm of consumer marketing, these findings can also be applied to political advertising to persuade or sway potential voters.

For more difficult-to-comprehend product messages (e.g. those said at a relatively fast rate of three words per second), it may be more effective to use just one narrator. Otherwise, it may be worthwhile for the video to feature multiple narrators to leverage the voice numerosity effect. This can not only enhance the extent to which consumers are influenced by a message, but also their willingness to pay for the target product.