Birthday-number effect
First reported in 1997 by Japanese psychologists Shinobu Kitayama and Mayumi Karasawa, the birthday-number effect has been replicated in various countries.
One lab study revealed an increase in a favourable attitude towards prices when they were secretly manipulated to match subjects' birthday dates, thus resulting in a higher chance of purchase.
Some field research into the impact of the birthday-number effect on bigger life decisions (e.g. where to live) is controversial.
[13][14][15][16] In an online poll by Alex Bellos, a columnist for The Guardian, more than 30,000 people from all over the world submitted numbers, with 7 the most popular.
[17][B] Marketing researchers King and Janiszewski investigated number preference in a different way.
In 1985, Belgian psychologist Nuttin reported the unexpected finding that people tend to disproportionately prefer, unknowingly, the letters of their own name.
[21][22] In 1997, researchers Shinobu Kitayama and Mayumi Karasawa observed that studies repeatedly showed that Japanese people do not seek to maintain and enhance their self-esteem, unlike Europeans and Americans.
[28] Because by definition implicit self-esteem is not accessible to introspection, measures of it do not rely on direct self-reports but on the degree to which objects associated with the self generate positive versus negative thoughts.
Participants had to give ratings on a six-point scale, ranging from 1, if they disliked the number very much, to 6, if they liked it very much.
For each participant 50 relative liking scores were computed between the baseline of a number and the actual preference.
[37] Kitayama and Karasawa concluded that the patterns in the findings from both experiments were most consistent with the hypothesis that the preference is due to an attachment to the self.
These feelings leak out to stimuli that are closely associated with the self, not just names and birthdates, but also, implicitly, their constituent letters and numbers.
Zajonc found in his 1960s and 1980s lab studies that familiarity can strongly influence preference, and coined the term "mere exposure effect".
They speculated that the reason for this masking lies in the Japanese tendency to attend to negative, undesirable features by way of improving the self.
Blass, Schmitt, Jones, and O'Connell used US undergraduate students as participants to replicate the original study.
In their paper presented at the American Psychological Association's annual conference in Chicago, in August 1997, they reported the same result: a preference for birthday numbers.
When the researchers retested all seven implicit self-esteem measures, the birthday-number task was one of three that produced similar results.
The first group was asked to give quick, intuitive reactions stating preferences for the stimuli.
Earlier research by Koole, Smeets, van Knippenberg, and Dijksterhuis had already shown that the name-letter effect is influenced by a perceived threat.
[57] Falk, Heine, Takemura, Zhang and Hsu investigated the validity of implicit self-esteem measures to assess cultural differences.
In their meta-analysis of the name-letter effect, Stieger, Voracek, and Formann recommend using the ipsatized double-correction algorithm.
[66] The Number Preference Task has been used to measure implicit self-esteem in contexts as diverse as parenting[50] and mental habits.
A body of controversial research under the umbrella of implicit egotism, starting with Pelham, Mirenberg, and Jones, has investigated whether people unknowingly make life decisions based on their name letters or birthday numbers.
[72] Jones, Pelham, Carvallo and Mirenberg investigated the influence of number preference on interpersonal attraction.
The results showed that participants liked the profiles significantly more when the code matched their own birthday numbers.
[68] They also found that brides disproportionately chose their own birthday numbers and birth months as wedding dates.
Over 200 participants of an online survey were asked about an advertisement for a pasta dinner, where the price was secretly matched to the day of the month of their birthday.
The researchers found that matching numbers increased price liking and purchase intention.
They manipulated the prices in advertisements for pizza and a music streaming service to match the birthday (day, year) of the participants in their lab study.
Keller and Gierl concluded that there must be some prerequisites such as priming stimuli to trigger the effect, although they suggested it is possible that their participants, who all happened to have been born between 1990 and 1999, saw their birthyear as price so often in real life that it had become too common.
