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PubMed2003

Carryover effects of feeling socially transparent or impenetrable on strategic self-presentation.

The authors proposed that social orientations, such as feeling transparent or impenetrable, that are created in one context can carry over and interact with elements in a different context to influence strategic self-presentation. Participants in 2 experiments wrote narratives that made them feel transparent or impenetrable. Later, they believed they would discuss problems from a social intelligence test with other group members and believed they could do well or poorly on the problems on the basis of practice test feedback. Self-presentations of social intelligence revealed the hypothesized interactions. When transparent, participants adjusted their self-presentations to how well or poorly they expected to perform, but when impenetrable, they presented themselves positively regardless of performance expectations. These results mimic effects obtained when performance is actually made publicly accessible or inaccessible, broaden the conceptualization of strategic self-presentation, and call into question long-held assumptions surrounding public versus private manipulations.

Adolescent↗
PubMed2004

Heart strings and purse strings: Carryover effects of emotions on economic decisions.

We examined the impact of specific emotions on the endowment effect, the tendency for selling prices to exceed buying or "choice" prices for the same object. As predicted by appraisal-tendency theory, disgust induced by a prior, irrelevant situation carried over to normatively unrelated economic decisions, reducing selling and choice prices and eliminating the endowment effect. Sadness also carried over, reducing selling prices but increasing choice prices--producing a "reverse endowment effect" in which choice prices exceeded selling prices. The results demonstrate that incidental emotions can influence decisions even when real money is at stake, and that emotions of the same valence can have opposing effects on such decisions.

Adolescent↗
PubMed2002

Development of a new medium useful for the recovery of dermatophytes from clinical specimens by minimizing the carryover effect of antifungal agents.

Two surface-active compounds, egg lecithin and polysorbate 80, usually used as the deactivators of various preservatives were tested whether they also counteract either or all of the three major topical antifungal drugs, bifonazole (BFZ), lanoconazole (LCZ) and terbinafine (TBF). Both egg lecithin and polysorbate 80, when added to culture media up to final concentrations of 1.0 and 0.7%, respectively, antagonized the anti-dermatophytic activity of the three drugs in a concentration-dependent manner. A greater extent of antagonistic action was exerted when the two deactivators combined at their maximal levels tested were added; MIC's of BFZ were increased more than 30-fold and those of LCZ and TBF more than 200-fold compared with the values obtained in the absence of the deactivators. Using the agar medium supplemented with the combined deactivators, culture studies were carried out with skin tissues specimens taken from guinea pigs whose feet were infected with dermatophytes and subsequently treated with 1% topical preparations of the three antifungal drugs. The experimental data from this animal study demonstrated that the combined deactivators-supplemented medium yielded increased numbers of fungi compared with the basal medium. It looks, therefore, likely that the fungal recovery on the former medium more correctly reflects to actual fungal burden in the infected lesions than the latter. All these results suggest that the combined deactivators-supplemented medium is more useful for mycological evaluation of therapeutic efficacy of imidazole and allylamine drugs against dermatophytoses in both preclinical and clinical studies.

Administration, Topical↗
PubMedDate not supplied

Crossover studies with continuous variables: power analysis.

The crossover design is a sensitive means of determining the efficacy of new drugs because it eliminates between-subject variability. However, if the response in the first period carries on into the second (carryover effect) or if time factors cannot be kept constant in a lengthy crossover (time effects), its statistical power may be jeopardized. This may be equally true if a negative correlation exists between treatment responses. We recently demonstrated that the crossover design with binary variables is a powerful method even if correlation between treatment responses is negative. Power analysis of crossover trials with continuous variables has not been explicitly studied. Using the Scheffé model for the assessment of treatment effect, carryover effect, and time effect, we drew power curves of hypothesized crossover studies with different levels of correlation between drug response. We demonstrate that the sensitivity of testing is largely dependent on the levels of correlation between drug response. When positive, we have a great deal of sensitivity with which to test treatment effect and little sensitivity to test carryover or time effect. When negative, the opposite is observed. The correlation level in a crossover comparison is a major determinant of the sensitivity of testing. Treatments from one class with one mode of action frequently have a positive correlation and should be particularly considered for crossover comparisons. With treatment comparisons of totally different classes of drugs/modes of action, the opposite is true. It is hoped that this work affects the design of future crossover trials.

Algorithms↗
PubMed2002

Randomized, placebo-controlled, parallel group versus crossover study designs for the study of dementia in Parkinson's disease.

In studies of dementia, crossover designs are controversial, reflecting concerns about temporal stability of disease, confounding of treatment effects with period by treatment interactions and/or carryover effects. Carryover effects are differences in the lingering effect of treatments (placebo) into subsequent periods. In the context of a trial to study the effect of donepezil on dementia in patients with Parkinson's disease, we examine two-sequence crossover studies with two or four periods, and a four-sequence design with two periods. We quantify bias in estimated treatment effects due to carryover effects and explore the use of biased estimators in hypothesis testing. For hypothesis testing, type I error rates are valid if (1) repeated administration of treatment alters the outcome only for effective treatments and (2) carryover effects due to placebo following treatment periods are nonzero only for effective treatments. For crossover and parallel group designs, sample sizes are adjusted for reduced statistical power due to carryover effects and temporal changes in variance. For the proposed clinical study, we estimate that a single-period parallel group design with baselines would require 104 patients and take about 23 months to complete. A two-sequence, four-period parallel group design with baselines would require about 80 patients and about 20 months to complete. We conservatively assume a carryover effect of 50% of the treatment effect for a two-sequence four-period crossover design. The estimated treatment effect for this model may underestimate the true treatment effect by up to 13%. The sample size/study length requirements are 28 patients or 12.4 months, respectively, a substantial saving over either parallel group design. The cost of allowing for carryover in the sample size calculation is about 1.2 months of study time.

Bias↗
PubMed1994

Statistical considerations for design and analysis of a multiperiod crossover study to compare two treatments for migraine headache.

The purpose of this paper is to discuss a long-term, multiperiod crossover study to compare two treatments for migraine headache. Principal attention is given to the analysis of an example in which patients randomly received a treatment sequence with test drug for three migraine headaches and placebo for one. An issue that requires attention for this example is the influence of a carryover effect for test drug that was greater when placebo was the subsequent treatment than when test drug was the subsequent treatment. A way to address this issue without excessive loss of power is to consider tests of "total treatment effects," which are weighted averages across headaches of differences between average response to test drug and average response to placebo. Since these weighted averages are linear combinations of treatment effects and carryover effects, their use requires an argument that carryover effects are at least partly a further form of treatment effects. For the example in this paper, this argument is realistic because the test drug could have provided much better relief to migraine headache than other treatment patients might have previously used. A second purpose of the paper is to present some alternative designs for situations like that represented by the example. The structure of variances for alternative specifications for treatment comparison is provided for models of interest for these designs.

Cross-Over Studies↗
PubMed1994

Evaluation of alternative statistical models for crossover studies to demonstrate caffeine adjuvancy in the treatment of tension headache.

This paper discusses alternative statistical models for the analysis of six crossover studies to determine whether better relief of tension headache occurs from treatment with an analgesic plus caffeine (C) than with the analgesic alone (A) or with placebo (P). Each patient in these crossover studies randomly received a pair of distinct medications in such a way as to treat the first two of four headaches with the initial medication in the pair and to treat the third and fourth headaches with the last medication in the pair. In order to have greater power for the C versus A comparison, three times as many patients were randomly assigned to the A:C and C:A sequence groups as to the A:P, C:P, P:A, and P:C sequence groups. An issue of statistical interest for these crossover studies is the extent to which the possibility of unequal carryover effects of the three medications influences the roles of alternative models for data analysis and the interpretation of results. When carryover effects for all three medications are equal, univariate analysis of variance for the difference scores between the average response for the first two headaches and the average response for the third and fourth headaches for each patient provides nearly the same power for pairwise treatment comparisons as more comprehensive multivariate methods for all four headaches. However, for comparisons concerning carryover effects and for treatment comparisons with adjustment for carryover effects, multivariate methods encompassing all four headaches jointly can provide greater power than univariate analysis for difference scores, particularly when there is low intraclass correlation for responses within the same patient. Another noteworthy role for multivariate methods in situations with potentially unequal carryover effects is their capacity to clarify whether multiple types of carryover effects occur across the second, third, and fourth headaches in the respective sequence groups. Multivariate models with alternative specifications of carryover effects are fit to the data from the six crossover studies to compare C, A, and P by weighted least squares. The role of potential variation among centers is addressed in these analyses by the use of stratified proportional means over centers, means of center means, and means ignoring centers. The primary focus of attention in the respective analyses is the evaluation of treatment comparisons with and without adjustment for potential differences among carryover effects of the treatments.(ABSTRACT TRUNCATED AT 400 WORDS)

Caffeine↗
PubMed1985

A Bayesian analysis of the two-period crossover design for clinical trials.

Statisticians have been critical of the use of the two-period crossover designs for clinical trials because the estimate of the treatment difference is biased when the carryover effects of the two treatments are not equal. In the standard approach, if the null hypothesis of equal carryover effects is not rejected, data from both periods are used to estimate and test for treatment differences; if the null hypothesis is rejected, data from the first period alone are used. A Bayesian analysis based on the Bayes factor against unequal carryover effects is given. Although this Bayesian approach avoids the "all-or-nothing" decision inherent in the standard approach, it recognizes that with small trials it is difficult to provide unequivocal evidence that the carryover effects of the two treatments are equal, and thus that the interpretation of the difference between treatment effects is highly dependent on a subjective assessment of the reality or not of equal carryover effects.

Analysis of Variance↗
PubMed2006

Within- word prosodic constraint on coarticulation in Japanese.

The present study addresses the question of how within-word prosodic constituent boundaries constrain V-to-V coarticulation in Japanese. The smallest prosodic unit that might affect V-to-V coarticulation is the bimoraic foot. The effect of the foot boundary is observed in the present study: the bimoraic foot constrains the extent of V-to-V coarticulation in both left-to-right and right-to-left directions. For the target vowel /a/, anticipatory V-to-V effects are stronger than carryover effects for both within-foot and across-foot conditions. Also, the foot constraint works more strongly on anticipatory than on carryover effects. Some idiosyncratic variation is observed across speakers; however, even some deviant behavior can partly be explained as the result of the interaction of C-to-V and V-to-V effects and speech rate. Coarticulation is observed to be the product of a complex process of constraint interaction.

Adult↗
PubMed2006

Carryover aquatic effects on survival of metamorphic frogs during pond emigration.

In organisms with complex life cycles, physiological stressors during early life stages may have fitness-level impacts that are delayed into later stages or habitats. We tested the hypothesis that body size and date of metamorphosis, which are highly responsive to aquatic stressors, influence post-metamorphic survival and movement patterns in the terrestrial phase of an ephemeral pond-breeding frog by examining these traits in two populations of northern red-legged frogs (Rana aurora aurora). To increase variation of body size at metamorphosis, we manipulated food availability for 314 of 1045 uniquely marked tadpoles and estimated the probability that frogs survived and emigrated using concentric rings of drift fencing surrounding ponds and Bayesian capture-recapture modeling. The odds of surviving and emigrating from the ponds to the innermost drift fences, approximately 12 m, increased by factors of 2.20 (95% credibility intervals 1.39-4.23) and 2.54 (0.94-4.91) with each millimeter increase in snout-vent length and decreased by factors of 0.91 (0.85-0.96) and 0.89 (0.80-1.00) with each day's delay in metamorphosis for the two ponds. The odds of surviving and moving to the next ring of fencing, 12 m to approximately 40 m from the ponds, increased by a factor of 1.20 (0.45-4.06) with each millimeter increase in size. Our results demonstrated that body size and timing of metamorphosis relate strongly to the performance of newly metamorphosed frogs during their initial transition into terrestrial habitat. Carryover effects of aquatic stressors that reduce size and delay metamorphosis may have population-level impacts that are not expressed until terrestrial stages. Since changes in both aquatic and terrestrial systems are implicated in many amphibian declines, quantifying both immediate and delayed effects of stressors on demographic rates is critical to sound management.

Age Factors↗
PubMed1991

Studies of women eating diets with different fatty acid composition. II. Urinary eicosanoids and sodium, and blood pressure.

Dietary fatty acid composition is known to affect various aspects of eicosanoid metabolism. This research was conducted to evaluate effects of a diet similar to the US average consumption in 1974 (40 en% fat, polyunsaturated to saturated fatty acid ratio, P/S = 0.3) or a diet modified to contain 30 en% fat, P/S = 1.0, on eicosanoid metabolism in young women. Following a period on self-selected diets, women in Nebraska and Iowa were fed the diets for 28-day periods in a crossover design. Urinary eicosanoids, sodium (Na) excretion, and blood pressure were determined. Diet effects were confounded by carryover effects. For urinary eicosanoids the sequence of higher saturated fat (SFA) followed by lower SFA resulted in significantly greater excretion, whereas the reverse order of diets did not cause significant changes. Diastolic blood pressure was not affected by diet, but systolic pressure was lower with the modified diet in the lower to higher-SFA sequence. The change from self-selected to experimental diets does not seem to account for the carryover effects. The interpretation is that linoleate is depleted from tissues more slowly than it is repleted. Effects upon Na excretion were related to SFA more than to linoleate in the diet.

Adult↗
PubMed2005

Enactment enhances integration between verb and noun, but not relational processing, in episodic memory.

Improved recall has consistently been demonstrated following motor activation at encoding (SPT), compared to traditional verbal learning (VT). Enhancements of item-specific processing and relational processing have been proposed as possible mechanisms to account for this SPT effect. There is ample evidence supporting the notion of enhanced item-specific processing, however it is still unclear whether enhancement of relational processing contributes to improved recall. In the present study, 2 experiments were designed to address this issue. In Experiment 1, memory under 2 encoding conditions (VT vs. SPT) and 3 recall conditions (free recall vs. category-cued recall vs. verb-cued recall) were studied in 3 large samples (N= 500-600). Experiment 2 replicated the findings of Experiment 1, and controlled for the use of actual objects, short-term memory effects, and carryover effects, in Experiment 1. The results in both experiments showed an interaction between type of encoding and type of recall. Verb-cued recall was affected differently by SPT encoding, as compared to category-cued recall and free recall. The results indicate that enhanced integration between verb and noun is an effect of SPT encoding, whereas enhanced relational processing is not.

Adult↗
PubMed1984

Vowel-to-vowel coarticulation in Catalan VCV sequences.

Electropalatographic and acoustical data on vowel-to-vowel (V-to-V) coarticulatory effects were obtained for Catalan VCV sequences, with the consonants representing different degrees of tongue-dorsum contact (dorsopalatal approximant [j], alveolo-palatal nasal [eta], alveolo-palatal lateral [lambda], and alveolar nasal [n]). Results show that the degree of V-to-V coarticulation in linguopalatal fronting and F2 frequency varies monotonically and inversely with the degree of tongue-dorsum contact, carryover effects being larger than anticipatory effects. The temporal extent of coarticulation also varies with the degree of tongue-dorsum contact, much more so for anticipatory effects than for carryover effects. Overall, results indicate that V-to-V coarticulation in VCV sequences is dependent on the mechanical constraints imposed on the tongue dorsum to achieve dorsopalatal closure during the production of the intervening consonant. Moreover, anticipatory effects, but not carryover effects, involve articulatory preprogramming.

Alveolar Process↗
PubMed2001

Effects of dietary fat on growth performance and carcass characteristics of growing-finishing pigs reared in a commercial environment.

We conducted two experiments to evaluate the effects of added choice white grease on performance and carcass merit of barrows and gilts reared under commercial conditions. Pigs were housed either 20 (Exp. 1) or 25 (Exp. 2) per pen and were provided 0.67 m2 of pen space per pig. Diets were based on corn and soybean meal and fed in a meal form. The proportion of soybean meal was increased in diets with added fat to maintain the same calorie:lysine ratio in all diets within a weight phase. In Exp. 1, 480 pigs were fed diets with 0, 2, 4, or 6% fat. Total lysine contents of the control diets were 1.21, 0.88, and 0.66% during the weight phases 36 to 59, 59 to 93, and 93 to 120 kg, respectively. Gain:feed was increased linearly (P < 0.01) due to fat addition in all weight intervals and over the total experiment. The effect of added fat on ADG was not consistent among the weight phases; a linear (P < 0.01) improvement was found from 36 to 59 kg, but no effect was found during the heavier weight phases. Over the total experiment, however, ADG was improved (P < 0.01) linearly. Carcass traits were not affected by treatment. Experiment 2 used 900 pigs to evaluate possible carryover effects on performance and carcass merit from feeding 6% fat. The experiment was divided into four phases: 25 to 45, 45 to 70, 70 to 90, and 90 to 115 kg; lysine contents of the control diets fed in each phase were 1.23, 1.05, 0.81, and 0.63%, respectively. The six treatments consisted of no added fat throughout the experiment or 6% added fat fed from 25 to 45 kg, 25 to 70 kg, 25 to 90 kg, 25 to 115 kg, or 45 to 70 and 90 to 115 kg. Carryover effects for ADG and G:F (P < 0.07) were found for the 90- to 115-kg interval and for ADFI and ME intake (P < 0.05) for the 45- to 70- and 70-to 90-kg intervals. When fat was added in the previous weight interval, ADG and G:F were improved and ADFI and ME intake were decreased in the subsequent weight interval. Pigs fed fat from 25 to 115 kg had more (P < 0.05) backfat and lower (P < 0.05) carcass leanness than pigs on the other treatments. These data suggest that fat can be added or removed from diets of growing-finishing pigs without any detrimental carryover effects. In fact, the positive carryover effect on ADG and G:F from 95 to 115 kg suggests that feeding fat from 25 to 95 kg will maximize performance over the total growing-finishing period but minimize any detrimental effects of added fat on carcass leanness.

Animal Feed↗
PubMed2006

Exposure, postexposure, and density-mediated effects of atrazine on amphibians: breaking down net effects into their parts.

Most toxicology studies focus on effects of contaminants during exposure. This is disconcerting because subsequent survival may be affected. For instance, contaminant-induced mortality can be later ameliorated by reduced competition among the survivors, a concept we refer to as "density-mediated compensation." Alternatively, it can be exacerbated by toxicant effects that persist or appear after exposure, a phenomenon we term "carryover effects." We developed a laboratory framework for testing the contribution of exposure, density-mediated, and carryover effects to net survival, by exposing embryos and larvae of the streamside salamander (Ambystoma barbouri) to atrazine (0, 4, 40, 400 ppb; 3 ppb is the U.S. drinking water maximum) and quantifying survival during and 14 months after exposure. Atrazine is the most commonly used herbicide in the United States and a documented endocrine disruptor. We show that atrazine-induced mortality during exposure was ameliorated by density-dependent survival after exposure, but complete density-mediated compensation was precluded by significant carryover effects of atrazine. Consequently, salamanders exposed to >or=4 ppb of atrazine had significantly lower survival than did control animals 14 months postexposure. The greatest change in survival occurred at low exposure concentrations. These nonlinear, long-term, postexposure effects of atrazine have similarities to effects of early development exposure to other endocrine disruptors. Together with evidence of low levels of atrazine impairing amphibian gonadal development, the results here raise concerns about the role of atrazine in amphibian declines and highlight the importance of considering persistent, postexposure effects when evaluating the impact of xenobiotics on environmental health.

Animals↗
PubMed2001

The effect of wearing a back belt on spine kinematics during asymmetric lifting of large and small boxes.

STUDY DESIGN: A crossover design was used to evaluate kinematic measurements collected with an infrared-based motion measurement system. OBJECTIVES: To evaluate belt effects on spine kinematics during asymmetric lifting of large and small boxes and to test for carryover effects between trials from belts. SUMMARY OF BACKGROUND DATA: Conflicting evidence in the literature exists regarding whether belts are beneficial or detrimental to manual material handlers. Studies have not examined belt effects when lifting different sized boxes, nor carryover effects from belts. METHODS: Twenty-eight subjects with manual-handling experience (17 male and 11 female) were randomly assigned to lift either a large or small box (weighing 9.4 kg), from a sagittally symmetric origin at pallet height to a 79 cm height, 60 degrees to the right. Spine flexion, lateral bending and twisting, hip and knee flexion, and angular velocity measurements of the torso with respect to the pelvis were collected for each of three lifting periods, 50 lifts each at 3 lifts per minute, with 18-minute breaks between periods. RESULTS: Belts significantly reduced maximum spine flexion, spine flexion and extension angular velocities, and torso left lateral bending angular velocity, and increased hip and knee flexion, regardless of box size. When lifting large boxes, belts significantly reduced torso right lateral bending and torso left twisting. No significant differential carryover effects were detected from belts. CONCLUSIONS: Subjects with belts lifted more slowly and used more of a squat-lift technique, regardless of box size. Belts reduced more torso motions while lifting large boxes.

Adolescent↗
PubMed1993

Interaction in cardiovascular crossover studies: the standard and the clinical analysis.

The crossover trial, which is considered the most powerful means of determining the efficacy of cardiovascular drugs, is frequently biased by treatment-by-period interactions. A second problem is that the standard analysis (Hills-Armitage analysis) for these biases is unreliable because of a low sensitivity. The author recently introduced an alternative method for the detection of interaction bias entitled the clinical analysis, because it looks at the clinical performance of the separate treatment groups in a trial and not, as in the standard analysis, at the means of the groups. In a mathematical model this analysis was capable of detecting interaction at a 30% lower level than the standard analysis. The present study was undertaken to show not only that the clinical analysis performs better than the standard but also that it enables the investigator to differentiate among different types of interactions, eg, physical carryover effect, rebound phenomenon, and psychological carryover effect.

Bias↗