Jörn Alexander Quent 05 May 2021
Version: 1.8
License: GPL-2
URL: https://github.com/JAQuent/nBack
Contact: alex.quent (at) mrc-cbu.cam.ac.uk
Please recognise this work by citing it.
I generally followed the approach described by Jaeggi and colleagues (2010; see section 2.2.1.1). Non-verbal stimuli - eight 8-points shapes (number 14, 15, 17, 18, 20, 22, 23, and 27) and two 12-points shapes (number 20 and 24) taken from Vanderplas and Garvin (1959) - are presented to subjects in sequence who are prompted to press the right control key if a stimulus is identical to the stimulus presented n-times back. No key press is required if the stimulus is a non-target. The black stimuli are presented on a white screen for a duration of 500 msec with an interstimulus interval (ISI) of 2500 msec. Therefore the subjects maximally have 3000 msec to give their response. The test levels increases from 2-back to 4-back; each level comprises three blocks, which amounts to nine blocks in total. Each block includes six targets and 14 + n non-targets. I ensure that the same stimulus is not repeated more than three times in a row. Reaction times, hits, false alarms, misses, correct rejections are recorded.
I am sorry that the instructions of the task are in German.
- Import the data:
data <- read.table("results/nBack_example.dat",
header= FALSE)
names(data) <- c('subjectNumber', 'date', 'time', 'trialNumber', 'stimulus', 'level', 'block', 'corrAnswer', 'response', 'correctness', 'RT', 'StimulusOnsetTime1','StimulusEndTime1', 'trialTime')
head(data)## subjectNumber date time trialNumber stimulus level block
## 1 1 20171109 150556 1 8 1 1
## 2 1 20171109 150556 2 8 1 1
## 3 1 20171109 150556 3 5 1 1
## 4 1 20171109 150556 4 5 1 1
## 5 1 20171109 150556 5 3 1 1
## 6 1 20171109 150556 6 1 1 1
## corrAnswer response correctness RT StimulusOnsetTime1
## 1 0 0 4 -99.0000 14.68156
## 2 1 1 1 634.4812 16.71541
## 3 0 0 4 -99.0000 16.43049
## 4 1 1 1 953.1878 16.28229
## 5 0 0 4 -99.0000 17.17728
## 6 0 0 4 -99.0000 16.60908
## StimulusEndTime1 trialTime
## 1 3048.1452 5548.211
## 2 667.8344 3167.889
## 3 3047.9408 5548.004
## 4 985.9618 3486.016
## 5 3034.7877 5534.839
## 6 3033.4444 5533.497
An 1 in column correctness means hit, a 2 means false alarm, a 3 means miss and a 4 means correct rejection. Based on this, we can calculate the error rate
data$errorRate <- 0
data$errorRate[which(data$correctness == 2 | data$correctness == 3)] <- 1and aggregate it across the levels.
library(plyr)
rates <- ddply(data, c('level'), summarise, errorRate = mean(errorRate))Then, we can display the error rate as the function of n-back level.
library(ggplot2)
ggplot(rates, aes(x = level, y = errorRate)) +geom_line() + labs(x = 'n-back level', y = 'Error rate', title = 'Example data')
In Versions < 1.8, there was a bug so that the ISI was larger than it was supposed to be when no response is given.
Samuel D McDougle, Ian C Ballard, Beth Baribault, Sonia J Bishop, Anne G E Collins, Executive Function Assigns Value to Novel Goal-Congruent Outcomes, Cerebral Cortex, 2021;, bhab205, https://doi.org/10.1093/cercor/bhab205
Lei, H., Mochizuki, Y., Chen, C. et al. Sex difference in the weighting of expected uncertainty under chronic stress. Sci Rep 11, 8700 (2021). https://doi.org/10.1038/s41598-021-88155-1
Nakagawa T, Koan I, Chen C, Matsubara T, Hagiwara K, Lei H, Hirotsu M, Yamagata H, Nakagawa S. Regular Moderate- to Vigorous-Intensity Physical Activity Rather Than Walking Is Associated with Enhanced Cognitive Functions and Mental Health in Young Adults. Int J Environ Res Public Health. 2020 Jan 18;17(2):614. https://doi.org/110.3390/ijerph17020614
Jaeggi, S. M., Studer-Luethi, B., Buschkuehl, M., Su, Y.-F., Jonides, J., & Perrig, W. J. (2010). The relationship between n-back performance and matrix reasoning - implications for training and transfer. Intelligence, 38(6), 625-635. https://doi.org/10.1016/j.intell.2010.09.001
Vanderplas, J. M., & Garvin, E. A. (1959). The association value of random shapes. Journal of Experimental Psychology, 57(3), 147-154. https://doi.org/10.1037/h0048723
n-back task.
Copyright (C) 2017 Jörn Alexander Quent
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