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    The effects of group size on mock jury decision making : a thesis presented in partial fulfilment of the requirements for the degree of Master of Arts in Psychology, at Massey University
    (Massey University, 1993) Dunn, Karyn
    The present investigation was a partial replication and extension of Saks' (1977) study on the effects of group size on mock jury decision making. Mock juries of size 4, 6, and 12 were formed by randomly assigning 232 student volunteer subjects to one of 30 groups, or to the condition where subjects worked alone (N=12 individuals). The case used was a written transcript adapted from Saks (1977). After reading the transcript, groups deliberated until they reached a verdict. Overall, it was found that groups of 12 came to the correct verdict more often and deliberated the longest, groups of 6, unexpectedly, produced the most hung juries, and the individuals recalled the least amount of the testimony. Groups of 4 perceived their group as being the most fair and were also the most satisfied with their group's decision. They also rated their influence on the decisions made by other members of the group as the highest. In all groups, there was a shift in the pre- and post-deliberation guilt ratings toward the group verdict, indicating an effect of group polarisation, and discussion also increased individuals' confidence in their rating of guilt, providing some support for the model of group influence proposed by Myers and Lamm (1976). In general, the results support previous findings and add to the growing literature which suggests that the effect of jury size is a complex phenomenon requiring more investigation.
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    Exploring the effect of group polarisation on perceived invulnerability in general aviation pilots : a thesis presented in partial fulfilment of the requirements for the degree of Master of Aviation at Massey University
    (Massey University, 2008) Lee, Seung Yong
    Although both perceived invulnerability and group polarisation are well known psychological phenomena, there has not been any research conducted to examine the effect of group polarisation on the level of perceived invulnerability amongst general aviation pilots. Two studies were conducted to measure the level of perceived invulnerability amongst general aviation pilots and to test whether the level of perceived invulnerability was affected due to group polarisation. The first study tested 34 pilots. Although the majority of the pilots exhibited perceived invulnerability, there was no evidence suggesting that low level group interaction induced group polarisation leading to an increase in individual's level of perceived invulnerability. The second study examined 78 pilots. Although the majority of the participants displayed perceived invulnerability, there was no evidence suggesting that high level group interaction resulted in group polarisation leading to an increase in individual's level of perceived invulnerability. There was no evidence that the two experimental manipulations (low group interaction and high group interaction) differed in effectiveness, as the effect size between studies I and II did not significantly differ. Although it is of some concern to general aviation safety that the majority of the pilots in both studies exhibited perceived invulnerability, the level of perceived invulnerability does not appear to be increased by a group polarisation effect. The latter finding is consistent with safe operations, having found no evidence that multi-crew operations lead to increased levels of perceived invulnerability. In addition to the implication of the current findings, limitations of the present study, possible areas for further research and recommendations are presented.