Using genetic programming to discover nonlinear variable interactions

Psychology has to deal with many interacting variables. The analyses usually used to uncover such relationships have many constraints that limit their utility. We briefly discuss these and describe recent work that uses genetic programming to evolve equations to combine variables in nonlinear ways in a number of different domains. We focus on four studies of interactions from lexical access experiments and psychometric problems. In all cases, genetic programming described nonlinear combinations of items in a manner that was subsequently independently verified. We discuss the general implications of genetic programming and related computational methods for multivariate problems in psychology.     

Exploring issues of personality measurement and structure through the development of a short form of the Eysenck Personality Profiler

In this article, we develop a revised short form of the original Eysenck Personality Profiler (EPP; H. J. Eysenck & Wilson, 1991). In addition, we address topics of broad theoretical importance such as the recurrent empirical finding of correlations between conceptually orthogonal personality dimensions and the possibility that gender differences in these dimensions are partly spurious. In Study 1 (N = 227), we demonstrate that the existing short form of the EPP (EPP-SF; H. J. Eysenck, Wilson, & Jackson, 1996) provides a poor fit to the data and we develop a revised well-fitting version. In Study 2, we retest this version on an independent new sample (N = 3,374) where it is again found to fit the data well. We show that most of the structural and measurement parameters of the revised EPP-SF are invariant across genders. Structured means analysis indicated a significant gender difference in Psychoticism, with men scoring higher than women, but no differences in Extraversion or Neuroticism. Our discussion focuses on issues concerning personality measurement and structure, including an examination of the role of confirmatory factor analysis in personality research.     

Semantics and semantic errors: implicit access to semantic information from words and nonwords in deep dyslexia

In this paper we describe dissociations of implicit versus explicit access to semantic information in a patient with deep dyslexia. This acquired reading disorder is characterized by the production of morphological (e.g., SLEEP read as SLEEPING) and semantic errors (e.g., HEART read as BLOOD) and consequently provides a potential window into the operation of both aspects of the language system. The deep dyslexic patient in this study (JO) demonstrated implicit semantic access to items in a number of tasks despite the fact that she was unable to correctly read these items aloud. The findings from this study are consistent with a model of lexical deficits that distinguishes between explicit and implicit access to lexical representations on the basis of inhibitory processes.     

Are infant attachment patterns continuously or categorically distributed? A taxometric analysis of strange situation behavior

Contemporary attachment research is based on the assumption that at least three types of infant attachment patterns exist: secure, avoidant, and resistant. It is not known, however, whether individual differences in attachment organization are more consistent with a continuous or a categorical model. The authors addressed this issue by applying P. E. Meehl's (1973, 1992) taxometric techniques for distinguishing latent types (i.e., classes, natural kinds) from latent continua (i.e., dimensions) to Strange Situation data on 1,139 fifteen-month-old children from the NICHD Study of Early Child Care. The results indicate that variation in attachment patterns is largely continuous, not categorical. The discussion focuses on the implications of dimensional models of individual differences for attachment theory and research.     

The sanctity of life: The role of purity in attitudes towards abortion and euthanasia

Although abortion and euthanasia are highly contested issues at the heart of the culture war, the moral foundations underlying ideological differences on these issues are mostly unknown. Given that much of the extant debate is framed around the sanctity of life, we argued that the moral foundation of purity/sanctity—a core moral belief that emphasises adherence to the “natural order”—would mediate the negative relationship between conservatism and support for abortion and euthanasia. As hypothesised, results from a nation-wide random sample of adults in New Zealand (N = 3360) revealed that purity/sanctity mediated the relationship between conservatism and opposition to both policies. These results demonstrate that, rather than being motivated by a desire to reduce harm, conservative opposition to pro-choice and end-of-life decisions is (partly) based on the view that ending a life, even if it is one's own, violates God's natural design and, thus, stains one's spiritual purity.     

Examining the between- and within-person effects of relative deprivation: Results from a 7-year longitudinal panel sample

Despite the extensive literature on relative deprivation theory, few studies have examined the longitudinal effects of individual- and group-based relative deprivation (IRD and GRD, respectively) on individual- and group-based outcomes, nor has research investigated the between-person and within-person effects of these constructs. Using two random intercept cross-lagged panel models, we address these oversights by estimating the between-person and average annual within-person associations IRD and GRD have with psychological distress and collective action support in a nation-wide longitudinal panel sample (N = 64,607). As expected, IRD and GRD were more strongly associated with psychological distress and collective action support, respectively, at the between-person level and contemporaneously at the within-person level. However, contrary to expectations, temporary departures in IRD and GRD predicted within-person increases in collective action support and psychological distress, respectively. These results raise questions about how and when people respond to inequality and provide the foundations for future longitudinal research.     

Voting in Ignorance: The Politics of Smooth-Sounding Names

The purpose of this experiment was to determine whether the attractiveness of political candidates' names would influence voter preferences, both when only the names were known and when politically relevant information was provided. The names and platforms of candidates in an actual election in which victory was attributed to a name effect were used in a straw poll of undergraduate subjects. Results showed a clear name effect when only names were presented. However, abstention was also quite common in this condition. When candidates' issue positions were also described, the name effect faded to nonsignificance. The results highlight the efficacy of relevant information in overcoming spurious influences on decisions.     

Sex typing: Construct and measurement issues

This study examined the relationships among commonly used measures of sex typing. A sample of 101 children, three to five years of age, were each seen on three occasions and administered six different measures of sex typing. The results showed that relations among the various measures of sex typing were quite modest for girls and only moderate for boys. Gender constancy scores did not mediate the relationships among measures for either girls or boys. The results are interpreted as supporting a multidimensional view of children's sex typing and as urging caution in generalizing results based on single measures of sex typing.     

Innovative uses of existing software in the teaching of psychodiagnostics

Too frequently, current, adaptable software programs are not used to their full potential for educational and clinical applications. Graduate psychology students often become familiar with computers and various programs for word processing and research applications, and now these students, using the same systems, can utilize and adapt database software to assist in psychodiagnostic decision-making. This paper discusses the development of one such system.