Date of Award

2015

Degree Type

Thesis

Degree Name

Doctor of Philosophy

School

School of Psychology and Social Science

Faculty

Faculty of Health, Engineering and Science

First Advisor

Dr Greg Dear

Second Advisor

Dr Maria (Ricks) Allan

Abstract

A reliable and valid instrument for the direct measurement of the relative strength of psychological needs is currently lacking. In response to this shortcoming, a new ipsative instrument, the Psychogenic Need Scale (PNS), is currently being developed; this is a 190-item forced-choice self-report measure that is based upon Murray’s psychogenic needs. For the development of a valid forced-choice instrument, it is critical to minimise the confounding effects of social desirability (the tendency for respondents to describe oneself in the most favourable light). Whilst other measures typically use specifically designed scales to detect social desirability confounds, this approach is unsuitable for forced-choice measures that require respondents to choose between paired statements. Instead, a preferable approach is to reduce or, ideally, eliminate social desirability confounds by ensuring that the two alternative statements in each item pair are equally desirable. However, because the PNS is in the preliminary stages of development, the statements’ relative social desirability levels had not yet been systematically investigated. Thus, it was not known whether or not the statements were equally desirable. Accordingly, I attempted this stage of the test's construction. Two main objectives were addressed. The first was to examine the test statements in order to determine whether or not they shared sufficiently equal levels of social desirability. The second was to equalise any differences (should they be detected) by rewording problematic statements to either reduce or increase their social desirability as needed. Upon initial investigation (Phase One of Study One), it was confirmed that there were differences among the statements. Thus, several attempts were made to equalise the relative social desirability levels. After a series of four studies, whereby statements with markedly high or low levels were repeatedly reworded and reexamined, some of the differences were effectively reduced. However, despite these reductions, the overall results demonstrate that problematic differences still exist. It was concluded that some statements in the PNS are likely to be inherently confounded with high or low social desirability and, thus, cannot be sufficiently adjusted without disrupting the validity of the constructs that they are supposed to measure. On that basis, it is likely that a valid forced-choice measure of Murray’s psychogenic needs is not achievable.

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