据我所知，问题出在你的数据上，而不是你的代码上，你发布的示例数据每个参与者/条件最多只有一行;参与者988没有FA_3或FA_4。如果您的真实的数据没有足够的数据用于参与者和条件的每个组合，那么sdTrim看起来只是参与者的平均值。
我对React时间数据不熟悉，但是您可能能够使用group_by and summarize from dplyr来完成您正在寻找的内容。
下面是一个基于示例数据的较大数据集的示例。

library(trimr)
set.seed(123)
participant <- c(rep("1", 100), rep("2", 100), rep("3", 100))
accuracy <- sample(x = c("1", "0"), size = 300, replace = TRUE, prob = c(.9, .1))
condition <- sample(x = c("hit_1", "FA_1", "hit_2", "FA_2", "hit_3", "FA_3", "FA_4", "hit_4", "hit_1", "FA_1", "hit_2", "FA_2", "hit_3", "hit_4"), size = 300, replace = TRUE)
rt <- sample(x = 250:625, size = 300)
new_data <- data.frame(participant, accuracy, condition, rt)

trimmedData <- sdTrim(data = new_data, 
                      minRT = 150, 
                      sd = 2, 
                      pptVar = "participant", 
                      condVar = "condition", 
                      rtVar = "rt", 
                      accVar = "accuracy", 
                      perParticipant = TRUE, 
                      returnType = "mean")

print(trimmedData)
  participant    FA_1   hit_1  hit_3   hit_2    FA_4    FA_2  FA_3   hit_4
1           1 439.800 477.250 433.85 440.375 426.286 439.500 508.8 457.429
2           2 477.067 489.933 466.50 360.000 405.000 387.533 427.2 428.364
3           3 398.333 446.500 438.00 362.077 445.000 432.333 419.2 497.125