Monday, 30 April 2012
Paul Rodway and his colleagues showed 100 participants (65 women) a questionnaire consisting of 17 questions, wherein each question featured five different pictures of the same item or type of item (e.g. five scenic views or five border terriers). Each set of five pictures was arranged in a horizontal row and the task for participants, depending on the question, was either to pick their most preferred or least preferred item. When picking out their favourite, the participants showed a clear preference for the central items; by contrast, no position bias was found when selecting their least favoured items.
The size of the preferential bias for central items was statistically significant but relatively modest in percentage terms. Central items were selected approximately 23 per cent of the time compared with the 20 per cent you'd expect if choices were random. The selection rate for items in other locations averaged below 20 per cent.
A second study was similar to the first, but this time each array of five items was arranged vertically - once again there was a bias for the central item. A final study used real objects - five pairs of identical white socks - pinned in a vertical array on a large piece of cardboard. Again, participants were asked to pick out their preferred option and again they showed a bias for the middle choice. Additionally, they showed a bias against picking the lower two options. The fact that the Centre Stage effect occurred for vertical arrays argues against explanations for the effect related to the brain's hemispheres biasing attention either to the left or right. Perhaps the cause has to do with cultural beliefs linking importance or prestige with being centrally located.
Rodway's team pondered the real-world implications of their findings. '"If item location influences preference during the millions of purchasing choices that occur every day, it will be exerting a substantial influence on consumer behaviour," they said. "Moreover, choices from a range of options are made in many other contexts (e.g. legal and occupational), and it remains to be investigated whether the central preference remains with other formats and whether it extends to other types of decision."
The new findings build on previous research showing that observers tended to overestimate the performance of quiz show contestants located in central positions, and tended to favour job candidates located centrally in a photograph.
Complicating matters, other research that's looked at items presented in a sequence or one at a time, has found that people show a bias towards items located in extreme positions in the sequence. For example, Wandi de Bruin in a 2005 study found that ice-skating competitors and Eurovision singers tended to receive higher scores if they performed later. On the other hand, if a choice array is perceived as a continuum - as in a questionnaire rating scale - there's evidence for a left-ward bias, perhaps caused by the dominance of the right hemisphere, which directs attention to the left-hand side of space.
Rodway, P., Schepman, A., and Lambert, J. (2012). Preferring the One in the Middle: Further Evidence for the Centre-stage Effect. Applied Cognitive Psychology, 26 (2), 215-222 DOI: 10.1002/acp.1812
Post written by Christian Jarrett for the BPS Research Digest.