Relationship between relaxation by guided imagery and performance of working memory.

This study tested the hypothesis that relaxation by guided imagery improves working-memory performance of healthy participants. 30 volunteers (both sexes, ages 17-56 years) were randomly assigned to one of three groups and administered the WAIS-III Letter-Number Sequencing Test before and after 10-min. treatment with guided imagery or popular music. The control group received no treatment. Groups' test scores were not different before treatment. The mean increased after relaxation by guided imagery but not after music or no treatment. This result supports the hypothesis that working-memory scores on the test are enhanced by guided imagery and implies that human information processing may be enhanced by prior relaxation.

Overconfidence: It Depends on How, What, and Whom You Ask.

Many studies have reported that the confidence people have in their judgments exceeds their accuracy and that overconfidence increases with the difficulty of the task. However, some common analyses confound systematic psychological effects with statistical effects that are inevitable if judgments are imperfect. We present three experiments using new methods to separate systematic effects from the statistically inevitable. We still find systematic differences between confidence and accuracy, including an overall bias toward overconfidence. However, these effects vary greatly with the type of judgment. There is little general overconfidence with two-choice questions and pronounced overconfidence with subjective confidence intervals. Over- and underconfidence also vary systematically with the domain of questions asked, but not as a function of difficulty. We also find stable individual differences. Determining why some people, some domains, and some types of judgments are more prone to overconfidence will be important to understanding how confidence judgments are made. Copyright 1999 Academic Press.

Debias the environment instead of the judge: an alternative approach to reducing error in diagnostic (and other) judgment.

Questions about how to improve human judgment and reasoning are of theoretical and practical interest, notwithstanding the continuing controversy over whether people are "rational". Improving judgment may involve modifying people's processes to fit their environments better, or vice versa. We illustrate the latter approach in a study of diagnostic reasoning in which subjects learned to distinguish two fictitious diseases. Prior findings suggest that people may judge the likelihood of a diagnostic category on the presence or absence of features that are typical of, rather than diagnostic of, the category. We varied the structure of the information provided to subjects without attempting to modify their judgmental processes. In an "independent" format, subjects learned about each disease separately; in a "contrastive" format, information about the two diseases was juxtaposed to highlight distinctive features. Subjects in the two conditions formed different disease concepts. Diagnoses following contrastive training were much closer to the statistically prescribed judgments based on likelihood ratios. Interventions that modify the environment may provide an alternative approach where it is difficult to modify people's processes. Effective design of such interventions is one motivation for directing research toward understanding how task characteristics affect the use of and the outcomes of judgment and reasoning processes.

Information selection and use in hypothesis testing: what is a good question, and what is a good answer?

The process of hypothesis testing entails both information selection (asking questions) and information use (drawing inferences from the answers to those questions). We demonstrate that although subjects may be sensitive to diagnosticity in choosing which questions to ask, they are insufficiently sensitive to the fact that different answers to the same question can have very different diagnosticities. This can lead subjects to overestimate or underestimate the information in the answers they receive. This phenomenon is demonstrated in two experiments using different kinds of inferences (category membership of individuals and composition of sampled populations). In combination with certain information-gathering tendencies, demonstrated in a third experiment, insensitivity to answer diagnosticity can contribute to a tendency toward preservation of the initial hypothesis. Results such as these illustrate the importance of viewing hypothesis-testing behavior as an interactive, multistage process that includes selecting questions, interpreting data, and drawing inferences.

Newborn body compositon and its relationship to linear growth.

Anthropometric measurements were made on 4,952 newborns from a Peruvian urgan population. Newborns characterized by high subcutaneous fat and high muscle had significantly greater birth weights and recumbent lengths when compared to their counterparts with low subcutaneous fat and muscle. Similarly, newborns characterized by high muscle and low fat had significantly greater birth weights and recumbent lengths that newborns characterized by low muscle and high fat. It is postulated that an increase in newborn protein and calorie reserves results in a greater increase in birth weight and recumbent length than an increase in calorie reserves alone. Evaluations of maternal antropometric characteristics indicate that variations in birth weight and recumbent length of the newborn are affected more by maternal nutritional status than by maternal stature.

Influence of maternal nutritional status on prenatal growth in a Peruvian urban population.

Anthropometric measurements were made on 4,952 mothers and their neonates from a Peruvian urban population. Based on age-specific percentiles, the mothers were separated into categories of short and tall stature, high and low fat, and high and low muscle. The study indicates that: (1) tall and short mothers characterized by similar subcutaneous fat and upper arm muscle area (whether high or low) had newborns with similar birth weight and recumbent length; (2) mothers characterized by high subcutaneous fat had heavier and fatter, but not longer, newborns than mothers with low subcutaneous fat; (3) mothers characterized by high upper arm muscle area had heavier, leaner and longer newborns than mothers with low upper arm muscle area; (4) mothers characterized by high muscle and high fat had heavier and longer newborns than mothers with high muscle and low fat; but (5) mothers characterized by high muscle and low fat had heavier and longer newborns than mothers with low muscle and high fat. Considering that subcutaneous fat and arm muscle area reflect calorie and protein reserves respectively, it is concluded that an increase in maternal calorie reserves results in increased infant fatness, but a lesser increase in linear growth. In contrast, an increase in maternal protein reserves does enhance both birth weight and prenatal linear growth.

PIP: Anthropometic measurements were made on 4952 mothers and their neonates from a Peruvian urban population in an effort to determine the effects of maternal nutritional status during pregnancy on prenatal growth. Measurements of height, pre-partum weight, upper arm circumference and triceps skinfolds were obtained using standard procedures as were measurements of birth weight, recumbent length, head circumference, thorax circumference, upper arm circumference and triceps skinfold thickness. On the basis of age-specific percentiles, the mothers were separated into categories of short and tall stature, high and low fat, and high and low muscle. The following were included among the findings: 1) tall and short mothers had newborns with similar birth weight and recumbent length; 2) mothers characterized by high subcutaneous fat had heavier and fatter, but not longer, newborns than mothers with low subcutaneous fat; 3) mothers characterized by high upper arm muscle area had heavier, leaner and longer newborns tha mothers with low upper arm muscle area; 4) mothers characterized by high muscle and high fat had heavier and longer newborns than mothers with high muscle and low fat; and 5) mothers characterized by high muscle and low fat had heavier and longer newborns than mothers with low muscle and high fat. On the basis that subcutaneous fat and arm muscle area reflect calorie and protein reserves respectively, it is concluded that an increase in maternal calorie reserves results in increased infant fatness but a lesser increase in linear growth. Increase in maternal protein reserves enhances both birth weight and prenatal linear growth.

A-B-O and Rh affinities between highland and lowland Quechua-speaking Peruvian populations.

According to the accounts of the Spanish chronicles and various historical analyses the Quechua-speaking population inhabiting the Province of Lamas in the Eastern Tropical Lowlands of Peru are descendants of the Chanca Tribes that migrated from the highlands about 500 years ago. The results of the present study indicate that in terms of the A-B-O and Rh systems the lowland Quechua-speaking population from the Province of Lamas and the highland Quechua population from the Province of Junin are more similar to each other than to other tropical tribes. Therefore, it is quite possible that the present lowland Quechua-speaking population from the Province of Lamas may be descendants of Andean populations.