People are more likely to judge the performance of a group based on member's that are labelled as first or number one than they are on any other member, according to new research led by Cass Business School academic Dr Janina Steinmetz.

Dr Steinmetz and her colleagues, Maferima Touré-Tillery of Northwestern University and Ayelet Fishbach from the University of Chicago, used seven separate studies to confirm that the performance of a group's first member can significantly influence people's decisions about the rest of the group.

One implication from this research can be found in supermarkets or retailers where numbered cash registers are in use - specifically on registers labelled with the numeral one.

Because the number one on a register labels its cashier as the group's first member, even though in reality it is an arbitrary number, a person who has a bad experience with the cashier at register number one will judge the whole store more harshly than if they had a bad experience at cashier number three, five or any other number.

Conversely, a pleasant experience at register number one will result in greater positivity about the store than it would at any other register.

"If the first group member to do something is bad then the whole group is seen as bad, if the first group member to do something is great then the whole group is seen as great, and this is much less the case if the middle or the last member does something," Dr Steinmetz said.

This is because, in people's experience, the first group member is often influential for the group -- a company's first employee shapes its culture much more than later employees, for example -- and people then apply this logic to first members in general.

In one research study, participants were presented with a scenario where five international cancer researchers are granted temporary work visas with a potential for extension.

When the participants were told that the scientist whose visa was approved first made a grave mistake they were more likely to judge the whole group of scientists as incompetent and less likely to support extending their work visas.

"When the first one makes the big mistake, people are more likely to say that all these scientists are terrible and we don't want them in the country," Dr Steinmetz said.

"People are more forgiving when the mistake is made by the scientist who receives their visa in the middle or last in the group and don't make such a harsh judgment."

This effect occurred although there was no reason to believe that the first researcher was special in any way, or that the group was actually incompetent. Instead, people were ready to deport the scientists because the bad apple in their group happened to be first in some arbitrary way when receiving the visa.

Other studies conducted during the research found the effect is replicated in judging students, athletes, and even racehorses.

"If the first horse of a group that are trained together runs very slowly in its race then other members of its group are expected to be slow as well and people would be less likely to bet on them," Dr Steinmetz said.

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The paper The First-Member Heuristic: Group Members Labelled "First" Influence Judgment and Treatment of Groups is published in the Journal of Personality and Social Psychology.