Research has repeatedly demonstrated
that the shape of a container can affect how people perceive its volume. One study published in the Journal of Consumer Research found that package shape can bias judgments about how much product a container holds. Containers that attract more visual attention can sometimes be perceived as containing more product than equivalent containers with less attention-grabbing shapes. The researchers found that this effect could persist across different container types and contexts. Familiarity with the unusual shape could reduce the effect, suggesting that experience can improve estimates.
Other research has examined the importance of height when people estimate volume. Consumers can rely heavily on a container’s vertical dimension when comparing packages, even though actual volume depends on several dimensions simultaneously. A tall package may therefore create a different impression from a shorter, wider package containing an equal amount. This kind of visual bias has been studied for decades in marketing and
consumer research. The important point is not that consumers are incapable of reading measurements. It is that visual impressions can influence judgment before those measurements are carefully considered.
The effect can continue even when the volume is printed directly on the package. Research involving bottles and cans found that elongated containers could be perceived as holding more than less elongated alternatives, despite the presence of quantity information. Experience with the product category could reduce this effect, but it did not necessarily eliminate visual bias completely. The research also found connections between perceived package volume and purchasing decisions under certain conditions. That demonstrates why package shape can matter commercially as well as aesthetically. A bottle is therefore communicating more than its written label alone.
Package dimensions can also influence consumers’ judgments of flexible packaging. Research on sachets found that dimensions and product weight affected impressions of size and product appeal. The
authors concluded that consumers can be susceptible to visual illusions when estimating package size. This does not establish that any particular commercial package is deceptive. It does show that appearance and actual quantity are separate pieces of information that consumers may process differently.
Larger packages can also influence expectations about serving and consumption. Studies summarized in academic research have found that package size can affect estimates of appropriate portions and subsequent food choices. Visual biases concerning package and portion size have therefore attracted attention not only from marketers but also from researchers studying nutrition and consumer behavior. These findings again demonstrate that physical presentation can shape perception. The effect depends on the product, consumer, context, and specific design rather than operating identically in every situation.
