The halo effect is a commonly cited reason to pay attention to aesthetics. This refers to people’s tendency to assume that when things are good in one way, they must also be good in other ways (for instance, that attractive people are smarter). Even if you discount the notion that attractive things work better, there is still good reason to make websites and products beautiful, because beautiful presentation in a sense rubs off on everything else connected with it.
We also use visuals to convey other favorable impressions, such as credibility. And this often pays off — after all, in a choice between a clearly amateur website and one that looks professionally designed, more people are going to feel comfortable trusting the better designed site. More trust means greater message acceptance and more sales.
Most of the time.
Researchers have identified certain circumstances where a credible-seeming source can actually harm the persuasive value of messaging. This finding underscores the importance of having strong copy even before considering presentation.