Taking account of time lags in causal models.

Although it takes time for a cause to exert an effect, causal models often fail to allow adequately for time lags. In particular, causal models that contain cross-sectional relations (i.e., relations between values of 2 variables at the same time) are unsatisfactory because they omit the values of variables at prior times, they omit effects that variables can have on themselves, and they fail to specify the length of the causal interval that is being studied. These omissions can produce severe biases in estimates of the size of causal effects. Longitudinal models also can fail to take account of time lags properly, and this too can lead to severely biased estimates. The discussion illustrates the biases that can occur in both cross-sectional and longitudinal models, introduces the latent longitudinal approach to causal modeling, and shows how latent longitudinal models can be used to reduce bias by taking account of time lags even when data are available for only 1 point in time.

Quantitative assessment of brain lesions.

The availability of precisely measurable dependent variables such as neurochemical activity, homeostatic changes, and behavioral patterns calls for more precise methods of measuring the independent variables of brain lesion research. In this study a method of measuring volumes of internal brain lesions and estimating amounts of damage to specific nuclei is described. Enlarged pictures of histologic sections through the lesion area are used. The structures to be measured are cut out of the pictures and weighed, and a weight-volume conversion formula is applied to yield the volumes of the structures. Two variations of this volumetric method are compared and evaluated. Various applications and advantages of quantified lesion data are discussed and appropriate statistical procedures are described.

Comparison of social judgments of creativity and intelligence.

Social judgment of creativity and intelligence was investigated by having subjects give trait ratings for stimulus profiles of actual art students based on abilities information alone, based on personality information alone, based on biographical information alone, and finally, based on the total set of all three types of cue information. Regression equations differed depending upon whether intelligence or creativity judgments were being predicted. For all types of information, there was a significant amount of variation unique to creativity judgments which could not be accounted for by intelligence judgments, and vice versa. However, the proposition of variation unique to each type of trait judgment was smallest when subjects had only abilities information available and was approximately four times larger when judgments were based on the total set of three types of cue information. Implications of this finding for the study of creativity are discussed.

An adding result in impression formation.

Ss were presented with a highly polarized piece of information, followed by a same-signed moderately polarized piece of information, and were asked whether the second piece of information led them to like the person describedmore, less, or just the same. The obtained percentage ofadding responses was 65%; that is, most of the responses indicated that Ss impression of the person described became more polarized following addition of moderately polarized information (p <.001). More adding was obtained for negatively than for positively evaluated adjectives (p <.05).