Our bias for the left-hand side of space could be distorting large-scale surveys. Past research has shown that when people are asked to bisect a horizontal line down the centre, most will cross the line too far to the left. This leftward bias is thought to stem from the right hemisphere – it plays a dominant role in allocating our attention and is also responsible for processing the left-hand side of space. It may also be related to a cultural tendency to read from left to right. Now Andrea Loftus and colleagues have reported this spatial bias could be distorting survey results.
The researchers presented two groups of students with the same questionnaire statements about their experience at university (e.g. “My course has been enjoyable”), except that one group answered using a 5-item Likert scale that ranged left-to-right, from ‘definitely disagree’ to ‘definitely agree’, whereas the other group answered using a scale that ranged left-to-right across the page, from ‘definitely agree’ to ‘definitely disagree’. The positive questionnaire statements were the same as those used by the Higher Education Funding Council for England (HEFCE) in its survey of 250,000 students.
In the current study, the students’ natural bias for the left meant those answering using the Likert scale that started on the left with ‘definitely agree’, responded with that answer to 27 per cent more statements than did the other group of students – that is, their views came out as more positive. By contrast, those students who answered using the scale that began on the left with ‘definitely disagree’ responded more often with ‘mostly disagree’, meaning their views came out overall as more negative.
The observation has profound implications for surveys, such as that conducted by the HEFCE, that seek respondents’ agreement, or not, with consistently positive or negative statements, and which use the same Likert scale for answers throughout. The researchers said one solution in the future is for the Likert scale direction to be reversed for half of the survey sample.
Nicholls, M.E.R., Orr, C.A., Okubo, M., and Loftus, A. (2006). Satisfaction Guaranteed. The Effect of Spatial Biases on Responses to Likert Scales. Psychological Science, 17, 1027-1028.