Christensen L, Miller J, Johnson D
Department of Psychology, Texas A&M University, College Station 77843.
J Gen Psychol. 1991 Jan;118(1):5-12. doi: 10.1080/00221309.1991.9711128.
The study investigated the independent and interactive effects of caffeine and expectancy on caffeine-related symptoms. High- and low-caffeine consumers were randomly assigned to either an expectancy or nonexpectancy instructional set and one of four caffeine doses. Subjects were administered the State-Trait Anxiety Inventory, (Spielberger & Gorsuch, 1970) and a Symptom Questionnaire (Christensen, White, Krietsch, & Steele, 1990) prior to and 45 min following consumption of one of the four caffeine doses. An analysis of covariance identified a significant main effect for the State-Trait Anxiety Inventory scores and significant main and interaction effects for four Symptom Questionnaire items. However, when the alpha levels were corrected for the increased probability of Type I error, using the Bonferroni procedure, these effects failed to achieve significance. These results suggest that previous reports of subjective caffeine effects are also suspect because of their failure to control for the increased probability of Type I error.
该研究调查了咖啡因和预期对与咖啡因相关症状的独立及交互作用。高咖啡因消费者和低咖啡因消费者被随机分配到预期或非预期指导组，以及四种咖啡因剂量之一。在摄入四种咖啡因剂量之一之前和之后45分钟，对受试者进行状态-特质焦虑量表（斯皮尔伯格和戈尔苏奇，1970年）和症状问卷（克里斯滕森、怀特、克里奇和斯蒂尔，1990年）测试。协方差分析确定状态-特质焦虑量表得分有显著主效应，症状问卷四个项目有显著主效应和交互效应。然而，当使用邦费罗尼程序对I型错误概率增加进行校正时，这些效应未达到显著水平。这些结果表明，之前关于咖啡因主观效应的报告也值得怀疑，因为它们未能控制I型错误概率增加的问题。
