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Geoffrey Keppel

Bio: Geoffrey Keppel is an academic researcher from University of California, Berkeley. The author has contributed to research in topic(s): Free recall & Recall. The author has an hindex of 23, co-authored 55 publication(s) receiving 10853 citation(s).
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01 Jan 1991

1,036 citations

Journal ArticleDOI

266 citations

Journal ArticleDOI
Abstract: \"Data Analysis for Research Designs\" covers the analytical techniques for the analysis of variance (ANOVA) and multiple regression/correlation (MRC), emphasizing single-degree-of-freedom comparisons so that students focus on clear research planning. This text is designed for advanced undergraduates and graduate students of the behavioral and social sciences who have an understanding of algebra and statistics.

342 citations

01 Jan 1989

245 citations

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Journal ArticleDOI
Zhijun Wei1, Jun Shan1, Reinhard Well, Xiaoyuan Yan1  +1 moreInstitutions (1)
01 Feb 2022-Geoderma
Abstract: In this study, soil-borne N2, NO, and N2O emissions induced by land use conversion and water management were investigated in intact soil cores under a helium/oxygen atmosphere by a robotized incubation system in combination with the N2O 15N site preference signature and molecular-based microbial analysis. The experiment consisted of five treatments: i) paddy-flooded (PF); ii) orchard-wet (OW, 70% WFPS); iii) orchard-dry (OD, 43% WFPS); iv) vegetable-wet (VW, 70% WFPS); and v) vegetable-dry (VD, 43% WFPS). The vessels of each treatment received 200 mg urea-nitrogen (N) (equivalent to 210 kg of urea-N ha−1), and soil moisture in the OW and VW treatments was adjusted to a higher constant moisture to simulate a scenario after irrigation or rainfall. The results showed that total gaseous N losses during the incubation period were 25.33 ± 0.33 kg N ha−1 in the PF treatment, whereas smaller losses were recorded in the OD and VD treatments (4.28 ± 2.04 and 9.75 ± 3.75 kg N ha−1, respectively). The potential contribution of bacterial denitrification to N2O emissions in the OD and VD treatments was 11.1% and 15.4% higher, respectively, than that in the PF treatment (58.8% ± 0.5%). Furthermore, the corresponding N2O/(N2O + N2) ratio in the OD and VD treatments decreased by 50% and 73.8%, respectively, relative to the ratio in the PF treatment (0.42 ± 0.01). Such changes indicated the crucial role of altered soil properties caused by land use conversion in regulating the production and consumption of N2O. Relative to the normal moisture (dry) condition, enhanced soil moisture increased total gaseous N losses in the orchard and vegetable soils by 386.9% and 67.4%, accompanied by a higher N2O/(N2O + N2) product ratio, but decreased the share of bacterial N2O by 11.1% and 15.4%, respectively. The changes in the abundance and community composition of soil denitrifiers caused by land use conversion from rice paddies to orchards and vegetable fields could partly explain the differences in gaseous N loss therein. These findings highlight the influence of land use conversion on soil gaseous N emissions and demonstrate that increased moisture in upland soils reduced the dominance of bacterial denitrification in N2O production.

Journal ArticleDOI
Yosef Sokol1, Yosef Sokol2, Chayim Rosensweig2, Chayim Rosensweig3  +3 moreInstitutions (4)
Abstract: Background Previous studies found that psychopathology is associated with distinct self-perceptions over time. Euthymic individuals report experiencing a self-enhancement bias, with self-appraisal increasing over time. In contrast, depressed individuals report viewing a personal decline from past to present and anticipated self-improvement from present to future. This study examined the association between the singular presence of anxiety and temporal self-appraisal. Methods Using the Depression Anxiety and Stress Scale, this study examined a depressed (n = 142), anxious (n = 95), comorbid depressed and anxious (n = 335), and euthymic group (non-depressed and non-anxious, n = 535), on a validated task of temporal self-appraisal. Results Anxiety has a unique association with temporal self-appraisal that differs from the other disorders examined in this study. Specifically, individuals with anxiety had a similar positive trend of self-view to the euthymic group; however, their overall trend was lower at each temporal point. Individuals with depression had a stable past-to-present self-view and an improving present-to-future self-view. Limitations The use of an online self-report sample without longitudinal assessment of variables, while sufficient for the intent of the present study, limits the potential extrapolation from this sample, as well as prevents the determination of the direction of causality. Conclusions While individuals with anxiety demonstrate a positive sense of improvement over time, their psychopathology is associated with a negative bias in their perception of their past, present, and future selves. These findings have important implications for clinicians regarding potential interventions and treatment for anxiety and depression.

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Lelia Samson1, Moniek Buijzen2Institutions (2)
01 Dec 2021-Appetite
Abstract: Research suggests that depictions of social groups can improve the processing of pronutritional media promoting healthy foods. Drawing on a framework of motivational processing, which regulates the automatic emotional and attentional responses to stimuli with adaptive significance to the organism (Cacioppo, Gardner, & Berntson, 1999; Compton, 2003; Ito, Cacioppo, & Lang, 1998), two mixed-factorial experiments examined how adolescents process pronutritional media depicting various social versus alone eating contexts. Based on motivational theories of information processing and emotional contagion, we predicted that pronutritional media depicting social eating contexts capture attention, emotion, and memory formation, indicative of appetitive motivational processing. Study 1 (N = 58; aged 12–18; 54% female) examined how the depicted social eating contexts improve the processing of pronutritional media by increasing their attentional selection, attentional processing, the emotional affect, and arousal responses to them. As the models' faces—which automatically attract priority processing—are oriented towards the foods in the social eating contexts, the pronutritional images depicting social eating contexts were predicted to attract greater attention and mental resources, and to further direct them to the foods. Study 2 (N = 165; aged 12–18; 53% female) investigated how the depicted social eating contexts further improve the processing of the healthy foods in the pronutritional media, by directing the visual attentional focus to the foods and attracting memory formation for them. Visual attentional focus was assessed through eye-tracking and memory was operationalized via visual recognition. As hypothesized, healthy foods became noticeable, highly-arousing, and memorable stimuli with adaptive significance to the organism when promoted through depictions of shared meals in social groups. The findings illustrate how healthy foods can be promoted more effectively through depictions of social eating contexts, and how the appetitive motivational processing explicates their greater effectiveness.

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Abstract: A challenge of large-scale oral communication assessments is to feasibly assess a broad construct that includes interactional competence. One possible approach in addressing this challenge is to use a spoken dialog system (SDS), with the computer acting as a peer to elicit a ratable speech sample. With this aim, an SDS was built and four trained human raters assessed the discourse elicited from 40 test takers that completed a paired oral task with both a human and a computer partner. The test takers were evaluated based on the analytic operational oral communication rating scales which included interactional competence, fluency, pronunciation, and grammar/vocabulary. Repeated-measures ANOVA indicated that fluency, pronunciation, and grammar and vocabulary were scored similarly across the two conditions, while interactional competence was scored substantially higher in the human partner condition. A g-study indicated that the computer partner was more reliable in assessing interactional competence, and rater questionnaire and interview data suggested the computer provided a more standardized assessment. Conversely, raters generally favored the human partner, in part because of its perceived authenticity and naturalness.

2 citations

Journal ArticleDOI
12 Nov 2021-Sleep
Abstract: STUDY OBJECTIVES Insufficient sleep is believed to promote positive energy balance (EB) and weight gain. Increasing weekend sleep duration to "recover" from weekday sleep loss is common, yet little is known regarding how weekend recovery sleep influences EB. We conducted a randomized controlled trial to assess how: (1) 2 days and 8 days of insufficient sleep and (2) ad libitum weekend recovery sleep impact EB (energy intake [EI] - energy expenditure [EE]). METHODS Following ten baseline days with 9 h per night sleep opportunities, participants completed one of three 10-day experimental protocols with ad libitum EI: control (9 h sleep opportunities; n = 8; 23 ± 5 years [mean ± SD]); sleep restriction (SR; 5 h sleep opportunities; n = 14; 25 ± 5 years); sleep restriction with weekend recovery sleep (SR + WR; 5 days insufficient sleep, 2 days ad libitum weekend recovery sleep, 3 days recurrent insufficient sleep; n = 14; 27 ± 4 years). RESULTS Twenty-four hour EB increased (p < 0.001; main effect) by an average of 797.7 ± 96.7 (±SEM) kcal during the 10-day experimental protocol versus baseline with no significant differences between groups. Percent change from baseline in 24 h-EE was higher (p < 0.05) on day 2 of insufficient sleep (SR and SR + WR groups; 10 ± 1%) versus adequate sleep (control group; 4 ± 3%). CONCLUSIONS In this between-group study, the effects of adequate sleep and insufficient sleep, with or without or weekend recovery sleep, on 24 h-EB were similar. Examining EB and body weight changes using within-subject cross-over designs and "free-living" conditions outside the laboratory (e.g. sleep extension) are needed to advance our understanding of the links between insufficient sleep, weekend recovery sleep and weight-gain.

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Author's H-index: 23

No. of papers from the Author in previous years