As a regular item in NeedToKnow: Trade Marks, I highlight a scientific or psychological study on consumer behaviour that has caught my attention.

There is no doubt that our ability to process, recognise and associate human faces is “hard-wired” into us. These skills are shown in babies, and obviously serve important social and survival needs (such as the need to recognise friends from enemies, and to discern emotions and communication cues).

But what effect does the image of a face in advertising or on packaging have on our buying behaviour? Can the presence of a face, or of a particular face, unconsciously drive us to make certain buying decisions?

If you think that we cannot possibly be so easily influenced by a mere photo, then let’s look first at the classic “lost wallet” study of Professor Richard Wiseman . In that study, researchers left wallets on the streets of Edinburgh and monitored how many were returned. The wallets either contained no photos or contained one of four photos - of a baby, a puppy, a family or an elderly couple. While only 15% of those wallets with no photo were returned, the highest returns were for the wallet with the baby photo (88%), followed by the puppy (53%), family (48%) and elderly couple (28%). Clearly, the image of the baby unconsciously triggered feelings of caring, altruism and generosity, which the finders acted upon.

This simple study suggests that, with an appropriately targeted photograph of a face, advertisers can similarly manipulate our feelings and buying behaviour. However, the two following studies show that you cannot just assume that any cute or attractive face will increase sales in all situations.

In the first study , researchers worked with a bank to send out 53,000 direct mail flyers announcing loan offers at different interest rates. The flyers were carefully manipulated to differ only in certain elements, such how they were worded, presented and what people’s faces were included (including men’s and women’s of different races). The researchers showed that the take-up of the offers was highly influenced by the manipulations. The face manipulations produced an interesting result: the inclusion of a photo of a woman (of any race) boosted the response rate from men, who were prepared to take up loan offers on high interest rates; the same effect was not seen on women, in their responses to either photos of men or women on the flyers. When targeting male banking customers, could it be the case that images of women, rather than of men, should be used in advertisements?

In the second study , researchers showed women a variety of neutral images, in dispersed with one of 20 images of a male or female face (which had been previously ranked on attractiveness). The women were asked to estimate how long each image (neutral or face) appeared on the screen. The women shown the attractive male face completely overestimated the duration that it appeared – suggesting that unconscious or autonomic brain processes were triggered, which made “time stand still”. Interestingly, no such effect was found for the any of the female faces shown. When targeting women’s fashion customers, could it be the case that images of attractive men, rather than of women, should be used in advertisements?

Unfortunately for marketers, and fortunately for us consumers, there is no “magical” face type that appeals to every type of consumer in every buying situation. Before the full-scale launch of any advertisement or packaging featuring a face, marketers need to conduct careful preliminary testing – as when it comes to face-selection, nothing can be assumed.