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README.md

iatgen (1.2.7)

iatgen (pronounced “I A T gen”) is an R package and Shiny App that builds and analyzes Qualtrics surveys that contain IATs (Implicit Association Tests; Greenwald et al., 1998) following a procedure developed by Carpenter et al. (2018; preprint available at https://psyarxiv.com/hgy3z/).

Specifically, Carpenter et al. developed procedures for “survey-software” IATs. These are IATs constructed out of modified survey elements that have been edited by adding custom JavaScript and HTML code. The R “iatgen” package was developed as a tool for customizing and pasting this code into Qualtrics so that functional IAT surveys can be rapidly built and analyzed.

What Exactly Does iatgen Do?

Several frequently asked questions about survey-software IATs and iatgen can be found at www.iatgen.wordpress.com. We recommend that people take a look at that web page if questions are not answered here.

First, iatgen is not a software tool for running IATs.

Iatgen does not run IATs. Qualtrics does! Instead, iatgen implements the survey-software IAT method automatically. That is, it configures code files (HTML, JavaScript) based on your input, copies that code into a Qualtrics survey template, and outputs a Qualtrics survey containing your desired IAT–all in just a few seconds. However, importantly, iatgen is not a ‘software tool’ for running the IAT. It is simply a method for implementing the survey-software IAT method. Qualtrics is the software tool that runs the IAT. It would, in theory, be possible for researchers to skip iatgen and configure Qualtrics IATs manually…but that would be laborious and prone to error (e.g., typos when coding).

Another benefit of iatgen is that it provides a suite of data analysis tools for processing the resulting data.

Please note that the iatgen R package is licensed only for non-commercial (e.g., academic) use under a Creative Commons (CC BY-NC 4.0) license. More details are provided under Licsense, below.

Please note that iatgen is not “official” IAT software; that is, it is neither produced nor endorsed by the IAT creators. Although we have painstakingly read the IAT literature and faithfully followed those procedures with our code, the official IAT software remains any software endorsed by the IAT’s creators. Although the use of Qualtrics as an IAT tool has been validated by Carpenter et al. (2018), this procedure and its code were generated by Carpenter et al. and were not provided or endorsed by the IAT’s creators.

Getting Started

The purpose of this tutorial is to walk you through how to use the iatgen package to build and analyze IATs.

Installation

iatgen can be installed on your computer using the devtools package. You first need to install this package if you do not have it. In addition, iatgen will use commands from the stringr package, so this should be installed as well.

install.packages("devtools")
install.packages("stringr")

Next, iatgen can be installed using the install_github() command from the devtools package:

devtools::install_github("iatgen/iatgen")

Loading iatgen

iatgen can be loaded as normal with library():

library(iatgen)

Getting Help

That the primary functions in iatgen have built-in help documentation. For example, detailed information on writeIATfull() can be obtained with ?writeIATfull().

Shiny App

Users who do not wish to use the R package can use our Shiny web app, which has the same features, at https://applibs.shinyapps.io/iatui2/.

Building an IAT

A brief vignette and summary of IAT build features is provided. Please read our methods paper (https://psyarxiv.com/hgy3z/) for more information.

Words-Only Example

All iatgen IATs run in Qualtrics. To build an IAT in Qualtrics, users must (1) configure JavaScript and HTML files, (2) copy them into Qualtrics, and (3) configure the Qualtrics files. This is all done automatically by iatgen, via the writeIATfull() function. An example looks like this.

writeIATfull(IATname="flowins",
             posname="Pleasant", 
             negname="Unpleasant",
             Aname="Flowers",
             Bname="Insects",
             catType="words",
             poswords = c("Gentle", "Enjoy", "Heaven", "Cheer", "Happy", "Love", "Friend"),
             negwords = c("Poison", "Evil", "Gloom", "Damage", "Vomit", "Ugly", "Hurt"),
             tgtType="words",
             Awords = c("Orchid", "Tulip", "Rose", "Daffodil", "Daisy", "Lilac", "Lily"),
             Bwords = c("Wasp", "Flea", "Roach", "Centipede", "Moth", "Bedbug", "Gnat"),
             
             #advanced options with recommended IAT settings
             n=c(20, 20, 20, 40, 40, 20, 40),
             qsf=TRUE, 
             note=TRUE,
             correct.error=TRUE,
             pause=250, 
             errorpause=300, #not used if correct.error=TRUE
             tgtCol="black",
             catCol="green",
             norepeat=FALSE
)

I walk through each argument here. More detailed information can be obtained with ?writeIATfull().

  • First, the user specifies IATname, which becomes part of the file names for the HTML and JavaScript files that are created. Because this is used for file names and folder names, it should be short and avoid any special characters.

  • Next, we specify the labels that appear on the screen (in the upper corners of the IAT). The positive category is named with the posname argument; the negative category is named with the negname argument; Target A is named with Aname; and Target B is named with Bname. Note that, for our purposes, we assume a “compatible” association is Target A + Positive, Target B + Negative. In other words, we assume Target A will be more associated with the positive category and Target B will be more associated with the negative category. At the end of the day a positive IAT D-score means that one was faster in the Target A + Positive, Target B + Negative (compatible) configuration.

  • Next, we need to tell R whether either (or both) categories and targets use text or image stimuli. This is done with the catType and tgtType arguments, which should be set to either images or words. If we set them to images (see below), we will specify the stimuli differently than if we set them to words.

  • Next, we set the stimuli. If words, we use the arguments poswords, negwords, Awords, and Bwords as appropriate. Those should be vectors of words or strings of text. If we use images, we instead specify posimgs/negimgs and/or Aimgs/Bimgs (as appropriate), which would be vectors of image URLs. This is illustrated below, so don’t worry about this now. This is all you need to set the basic information for the IAT.

  • Next, we enter “advanced” options. These are set by default, but it’s good to know what your script is doing, so let’s discuss them. First, we set n=c(20, 20, 20, 40, 40, 20, 40). This is the number of trials per block, a numeric vector of length seven. This means we have 20 trials in the first block, 20 in the second block, 20 in the third block, 40 in the fourth block (critical combined block), 40 in the fifth block (washout block with direction reversed; see Nosek et al., 2005 for rationale for setting this to 40), 20 in the sixth block, and 40 in the seventh block.

  • The qsf=TRUE argument is set (as it is by default) to tell R to build a Qualtrics Survey File *.QSF. If you don’t want this, set it to FALSE and R will instead create the JavaScript and HTML files manually for you in the user’s working directory (saved as .txt files).

  • The note=TRUE includes a note telling users what the keys are during the task. Some researchers use this to remind users that the task uses the “E” and “I” keys. Some people prefer these not on the screen.

  • The correct.error=TRUE tells R to write the code such that the timer continues until participants enter the correct response. Under this common IAT variant, errors will result in an error message on the screen that persists until the correct response is entered. If set to FALSE, then R will record whichever answer the user enters and display an error message that flashes on the screen only for as long as specified by errorpause (by default, errorpause=300 milliseconds).

  • The pause=250 argument tells R to make the duration between trials to be 250 milliseconds, or a quarter of a second.

  • The colors of the text stimuli and labels can be set. Typically, in an IAT, they are different for targets and categories (to reduce confusion). By default, they are set with tgtCol="black" and catCol="green" but can be set to any CSS color name.

  • The norepeat=FALSE option uses a random order of presentation of trials within each block. Please note that stimuli are selected for inclusion in the IAT by randomly sampling without replacement from stimuli pools (meaning that stimuli will not be selected more than once into a set of trials until ALL stimuli from that category have been sampled). However, in terms of the order in which those stimuli are displayed, setting this to TRUE will keep stimuli in the order sampled, meaning that a participant will also not see a duplicate until all other stimuli from that category have veen displayed.

Image-Based IATs

Targets, categories, or both can use images. Images should be sized 250 x 250 pixels in PNG format and hosted via the user’s Qualtrics account (tutorial at https://osf.io/ntd97/).

Then, tgtType and/or catType arguments are set to “images” (as appropriate), and poswords/negwords are replaced with posimgs/negimgs and/or Awords/Bwords are replaced with Aimgs/Bimgs (as appropriate). The only difference between the word stimuli vectors and the image vectors is that the image vectors are vectors of image URLs. For stability reasons and on the basis of our own testing, we strongly recommend users of images only host images on their own Qualtrics accounts and follow the guidelines found in the tutorial referenced above.

Because URLs are long, we recommend specifying vectors of images URLs in advance and referencing them in the function call:

goodjpg <- c("www.website.com/gentle.jpg",
             "www.website.com/enjoy.jpg",
             "www.website.com/Heaven.jpg",
             "www.website.com/Cheer.jpg")

badjpg <- c("www.website.com/Poison.jpg",
            "www.website.com/Evil.jpg.",
            "www.website.com/Vomit.jpg",
            "www.website.com/Ugly.jpg")

Ajpg <- c("www.website.com/Orchid.jpg",
             "www.website.com/Tulip.jpg",
             "www.website.com/Rose.jpg",
             "www.website.com/Daisy.jpg")

Bjpg <- c("www.website.com/Wasp.jpg",
            "www.website.com/Flea.jpg",
            "www.website.com/Moth.jpg",
            "www.website.com/Bedbug.jpg")

writeIATfull(IATname="flowins",
             posname="Pleasant", 
             negname="Unpleasant",
             Aname="Flowers",
             Bname="Insects",
             catType="images",
             posimgs = goodjpg,
             negimgs = badjpg,
             tgtType="images",
             Aimgs = Ajpg,
             Bimgs = Bjpg,
             
             #advanced options with recommended IAT settings
             n=c(20, 20, 20, 40, 40, 20, 40),
             qsf=TRUE, 
             note=TRUE,
             correct.error=TRUE,
             pause=250, 
             errorpause=300, #not used if correct.error=TRUE
             tgtCol="black",
             catCol="green"
)

The Qualtrics Survey

Detailed information about this Qualtrics survey is beyond the scope of this document and is discussed in depth in the Carpenter et al. (2018) preprint found at https://psyarxiv.com/hgy3z/.

Of note, however, is that (1) each IAT block is one question and (2) there are four permutations of the IAT exist, counterbalancing the left/right starting position for both Target A and the positive category. Because each IAT consists of 7 blocks, these occupy 28 survey questions (7 blocks x 4 permutations). These questions are named using both the question number (Q1-Q28) and a 3-digit code identifying which IAT permutation it comes from, based on the starting position of Target A (RP = Target A starts right, initially paired with positive; RN = starts left with negative; LP = starts left with positive; LN = starts left with negative). Thus, “Q9 RN2” is the second block in the IAT where Target A starts on the right side, initially paired with negative (i.e., incompatible block comes first). Researchers should carefully consult our manuscript prior to use.

Analysis

Once data are collected, iatgen can process the resultant data. Several data-analysis scripts and a user tutorial are provided via https://osf.io/ntd97/. However, a brief analysis vignette is provided here.

In this vignette, users were not asked to correct errors and therefore the “D600” algorithm is used. Note that you need to know how the IAT was conducted with respect to errors in order to select the correct analysis procedure. (This is one great reasons to build using an R script, where you can save a copy or even share your build script on a repository with materials, data, code, etc.).

Note too that data must be in the legacy Qualtrics CSV format. For data loaded to R, the row containing detailed question information is also deleted (per usual, when working with Qualtrics data).

First, the data are loaded:

#### LOAD THE IATGEN PACKAGE ####
library(iatgen)

#### READ YOUR DATA HERE AND SAVE IN R AS "DAT" ####
dat <- read.csv("IAT Flowers Insects.csv", header=T)

To analyse the IAT, the data must be collapsed into four variables representing practice/critical versions of the compatible and incompatible blocks. At present, these are scattered across four hard-coded permutations of the IAT representing left/right counterbalancing of the starting positions (naming of these variables is discussed above and in our manuscript at https://psyarxiv.com/hgy3z/). The next step in the analysis is to collapse this down using combineIATfourblocks():

### Collapse  IAT data down ####
dat$compatible.crit <- combineIATfourblocks(dat$Q4.RP4, dat$Q18.LP4, dat$Q14.RN7, dat$Q28.LN7)
dat$incompatible.crit <- combineIATfourblocks(dat$Q7.RP7, dat$Q21.LP7, dat$Q11.RN4, dat$Q25.LN4)

### Collapse  IAT practice blocks ####
dat$compatible.prac<- combineIATfourblocks(dat$Q3.RP3, dat$Q17.LP3, dat$Q13.RN6, dat$Q27.LN6)
dat$incompatible.prac <- combineIATfourblocks(dat$Q6.RP6, dat$Q20.LP6, dat$Q10.RN3, dat$Q24.LN3)

Following this, the researcher runs cleanIAT(). In this case, the researcher is careful to set an error.penalty=TRUE and error.penalty.ms=600 milliseconds, given that participants were not forced to correct errors (making this the D600 algorithm; had participants been forced to correct errors, this would have been error.penalty=FALSE, making it the D-built.in.error.penalty algorithm). This command is done and the result saved to an object for further use, typically named clean.

### Clean the IAT ### 
clean <- cleanIAT(prac1=dat$compatible.prac, 
                  crit1=dat$compatible.crit, 
                  prac2=dat$incompatible.prac, 
                  crit2=dat$incompatible.crit, 
                  
                  timeout.drop=TRUE, 
                  timeout.ms=10000, 
                  
                  fasttrial.drop=FALSE, 
                  
                  fastprt.drop=TRUE, 
                  fastprt.percent=.10, 
                  fastprt.ms=300, 
                  
                  error.penalty=TRUE, 
                  error.penalty.ms=600)

There are a few things to note in the cleanIAT().

  • First, the first four arguments (prac1, crit1, prac2, and crit2) represent the practice and critical versions of the compatible and incompatible blocks, respectively (see above).

  • In addition, following Greenwald et al. (2003)’s D-score algorithm, we have set a timeout such that trials above 10,000 ms are removed (timeout.drop=TRUE, timeout.ms=10000).

  • We have not set individual fast trials to be removed in the same manner (fasttrial.drop=FALSE) and instead follow the Greenwald et al. (2003) procedure of removing all data from participants who have more than 10% of responses under 300 ms (fastprt.drop=TRUE, fastprt.percent=.10, fastprt.ms=300). Note, however, that you could opt to remove fast trials instead of fast participants. In our experience, fast participants tend to have very high error rates (think: a participant pressing buttons randomly and quickly to skip the IAT). Thus, dropping fast participants seems to make sense in most contexts.

  • Finally, as noted above, we are adding an error penalty in analysis of 600 ms because participants were not required to correct errors (error.penalty=TRUE, error.penalty.ms=600). Note that the error.penalty argument is special in that it’s smart. Greenwald et al. (2003) suggested researchers could use two standard deviations instead of a fixed penalty. We have added that as an option with error.penalty="2SD". If you want to disable it (e.g., if participants corrected errors), then set it to error.penalty=FALSE).

The clean object is a list containing many things For detailed information see the built-in help file (?cleanIAT()). We focus on a few here.

First, the number of participants who completed the IAT using $skipped, a logical vector indicating whether each person completed an IAT or not:

### NUMBER OF PARTICIPANTS WHO COMPLETED THE IAT ###
sum(!clean$skipped)

## [1] 201

We see here that 201 people (which was the sample size) submitted a completed IAT for analysis.

Next, we can see the proportion of trials dropped due to exceeding 10,000 ms (as specified in our function call, above) with $timeout.rate:

### TIMEOUT DROP RATE (% of TRIALS) ###
clean$timeout.rate

## [1] 0.001285347

As we see here, it is 1/10 of 1% of trials…a very small amount.

Next, we can get diagnostics on the number of participants dropped due to overly fast responses with $fastprt.count and $fastprt.rate:

### FAST PARTICIPANT 'BUTTON MASHER' DROP COUNT AND RATE (% of SAMPLE) ###
clean$fastprt.count

## [1] 13

clean$fastprt.rate

## [1] 0.06467662

We see this is 13 participants, or approximately 6% of the sample.

If you wanted to know whether individual participants were dropped or not, simply request clean$drop.participant which returns a logical vector. This can be used, for example, to inspect those responses in greater detail.

clean$drop.participant

##     1     2     3     4     5     6     7     8     9    10    11    12 
##  TRUE  TRUE  TRUE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE FALSE FALSE 
##    13    14    15    16    17    18    19    20    21    22    23    24 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    25    26    27    28    29    30    31    32    33    34    35    36 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    37    38    39    40    41    42    43    44    45    46    47    48 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    49    50    51    52    53    54    55    56    57    58    59    60 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    61    62    63    64    65    66    67    68    69    70    71    72 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    73    74    75    76    77    78    79    80    81    82    83    84 
## FALSE FALSE FALSE FALSE FALSE  TRUE  TRUE FALSE FALSE FALSE FALSE FALSE 
##    85    86    87    88    89    90    91    92    93    94    95    96 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##    97    98    99   100   101   102   103   104   105   106   107   108 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##   109   110   111   112   113   114   115   116   117   118   119   120 
##  TRUE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE FALSE FALSE 
##   121   122   123   124   125   126   127   128   129   130   131   132 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE FALSE FALSE  TRUE 
##   133   134   135   136   137   138   139   140   141   142   143   144 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##   145   146   147   148   149   150   151   152   153   154   155   156 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##   157   158   159   160   161   162   163   164   165   166   167   168 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE 
##   169   170   171   172   173   174   175   176   177   178   179   180 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE  TRUE FALSE  TRUE FALSE 
##   181   182   183   184   185   186   187   188   189   190   191   192 
## FALSE FALSE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE FALSE FALSE FALSE 
##   193   194   195   196   197   198   199   200   201 
## FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE

It’s easy to index in this way. For example, imagine we wanted age statistics on these people:

dat$age[clean$drop.participant]

##  [1] 27 29 28 19 39 26 23 28 23 23 26 28 28

Next, How accurate were our retained participants? This is given with $error.rate:

### ERROR RATE ###
clean$error.rate

## [1] 0.07467388

We are less than 10%, which is considered typical for an IAT. The error rates of individual participants can also be viewed with:

clean$error.rate.prt

##           1           2           3           4           5           6 
##          NA          NA          NA 0.016666667 0.025000000          NA 
##           7           8           9          10          11          12 
## 0.075000000 0.150000000 0.058333333 0.166666667 0.050000000 0.033333333 
##          13          14          15          16          17          18 
## 0.288135593 0.033333333 0.025000000 0.133333333 0.091666667 0.041666667 
##          19          20          21          22          23          24 
## 0.133333333 0.058333333 0.041666667 0.025000000 0.008333333 0.068965517 
##          25          26          27          28          29          30 
## 0.050000000 0.016666667 0.091666667 0.050000000 0.091666667 0.050000000 
##          31          32          33          34          35          36 
## 0.058333333 0.025000000 0.066666667 0.141666667 0.116666667 0.016666667 
##          37          38          39          40          41          42 
## 0.183333333 0.050000000 0.041666667 0.041666667 0.091666667 0.116666667 
##          43          44          45          46          47          48 
## 0.066666667 0.066666667 0.175000000 0.166666667 0.183333333 0.050000000 
##          49          50          51          52          53          54 
## 0.041666667 0.066666667 0.168067227 0.066666667 0.050000000 0.041666667 
##          55          56          57          58          59          60 
## 0.116666667 0.058333333 0.033333333 0.058333333 0.050000000 0.041666667 
##          61          62          63          64          65          66 
## 0.125000000 0.000000000 0.083333333 0.275000000 0.125000000 0.041666667 
##          67          68          69          70          71          72 
## 0.075000000 0.058333333 0.033333333 0.058333333 0.100000000 0.000000000 
##          73          74          75          76          77          78 
## 0.116666667 0.041666667 0.041666667 0.058333333 0.025000000          NA 
##          79          80          81          82          83          84 
##          NA 0.067226891 0.200000000 0.091666667 0.016666667 0.158333333 
##          85          86          87          88          89          90 
## 0.158333333 0.008333333 0.100000000 0.116666667 0.041666667 0.216666667 
##          91          92          93          94          95          96 
## 0.116666667 0.041666667 0.025000000 0.066666667 0.091666667 0.083333333 
##          97          98          99         100         101         102 
## 0.025000000 0.116666667 0.041666667 0.050000000 0.100000000 0.050420168 
##         103         104         105         106         107         108 
## 0.033333333 0.133333333 0.058333333 0.008333333 0.008333333 0.033333333 
##         109         110         111         112         113         114 
##          NA 0.041666667 0.158333333 0.025000000 0.041666667 0.109243697 
##         115         116         117         118         119         120 
## 0.025210084 0.033333333 0.083333333          NA 0.083333333 0.091666667 
##         121         122         123         124         125         126 
## 0.058333333 0.042735043 0.075000000 0.066666667 0.141666667 0.075000000 
##         127         128         129         130         131         132 
## 0.025000000 0.083333333          NA 0.158333333 0.066666667          NA 
##         133         134         135         136         137         138 
## 0.075000000 0.133333333 0.000000000 0.091666667 0.058333333 0.066666667 
##         139         140         141         142         143         144 
## 0.066666667 0.058333333 0.208333333 0.075000000 0.141666667 0.008333333 
##         145         146         147         148         149         150 
## 0.025000000 0.175000000 0.116666667 0.200000000 0.050000000 0.000000000 
##         151         152         153         154         155         156 
## 0.116666667 0.116666667 0.116666667 0.066666667 0.016666667 0.066666667 
##         157         158         159         160         161         162 
## 0.085470085 0.041666667 0.016666667 0.041666667 0.041666667 0.025000000 
##         163         164         165         166         167         168 
## 0.075000000 0.100000000 0.025000000 0.108333333 0.133333333 0.016666667 
##         169         170         171         172         173         174 
## 0.016666667 0.066666667 0.083333333 0.058333333 0.050000000 0.041666667 
##         175         176         177         178         179         180 
## 0.058333333 0.058333333          NA 0.100000000          NA 0.025000000 
##         181         182         183         184         185         186 
## 0.066666667 0.050000000 0.033333333 0.041666667 0.050000000          NA 
##         187         188         189         190         191         192 
## 0.100000000 0.050000000 0.041666667 0.050000000 0.119658120 0.033333333 
##         193         194         195         196         197         198 
## 0.100000000 0.194915254 0.025000000 0.066666667 0.066666667 0.116666667 
##         199         200         201 
## 0.025000000 0.058333333 0.108333333

We can see here that dropped participants have an NA. However, if you wanted to know the error rate of dropped participants, you could re-run cleanIAT() without dropping (e.g., saved as clean.nodrop) and then request the error rates from that (e.g.,clean.nodrop$error.rate.prt[clean$drop.participant]).

You can also view the error rate for each of the four combined blocks with clean$error.rate.prac1, clean$error.rate.crit1, clean$error.rate.prac2 and clean$error.rate.crit2:

clean$error.rate.prac1

## [1] 0.05111821

clean$error.rate.crit1

## [1] 0.05004659

clean$error.rate.prac2

## [1] 0.115016

clean$error.rate.crit2

## [1] 0.09090909

Although not the primary means of analysis for the IAT, you see here just how many errors there are in the prac2 and crit2 blocks–the incompatible block. There are many other elements in this clean object. Take a look at the help file ?cleanIAT() to see what you can get. Or, look at the names():

names(clean)

##  [1] "skipped"                     "raw.latencies.prac1"        
##  [3] "raw.latencies.crit1"         "raw.latencies.prac2"        
##  [5] "raw.latencies.crit2"         "raw.stim.number.prac1"      
##  [7] "raw.stim.number.crit1"       "raw.stim.number.prac2"      
##  [9] "raw.stim.number.crit2"       "raw.correct.prac1"          
## [11] "raw.correct.crit1"           "raw.correct.prac2"          
## [13] "raw.correct.crit2"           "timeout.drop"               
## [15] "timeout.ms"                  "num.timeout.removed"        
## [17] "timeout.rate"                "num.timeout.removed.prac1"  
## [19] "num.timeout.removed.crit1"   "num.timeout.removed.prac2"  
## [21] "num.timeout.removed.crit2"   "fasttrial.drop"             
## [23] "fasttrial.ms"                "num.fasttrial.removed"      
## [25] "fasttrial.rate"              "num.fasttrial.removed.prac1"
## [27] "num.fasttrial.removed.crit1" "num.fasttrial.removed.prac2"
## [29] "num.fasttrial.removed.crit2" "fastprt.drop"               
## [31] "fastprt.ms"                  "fastprt.percent"            
## [33] "drop.participant"            "fastprt.count"              
## [35] "fastprt.rate"                "error.penalty"              
## [37] "error.num.prt"               "error.rate.prt"             
## [39] "error.rate"                  "error.rate.prac1"           
## [41] "error.rate.crit1"            "error.rate.prac2"           
## [43] "error.rate.crit2"            "clean.latencies.prac1"      
## [45] "clean.latencies.crit1"       "clean.latencies.prac2"      
## [47] "clean.latencies.crit2"       "clean.stim.number.prac1"    
## [49] "clean.stim.number.crit1"     "clean.stim.number.prac2"    
## [51] "clean.stim.number.crit2"     "clean.correct.prac1"        
## [53] "clean.correct.crit1"         "clean.correct.prac2"        
## [55] "clean.correct.crit2"         "clean.means.prac1"          
## [57] "clean.means.crit1"           "clean.means.prac2"          
## [59] "clean.means.crit2"           "diff.prac"                  
## [61] "diff.crit"                   "inclulsive.sd.prac"         
## [63] "inclusive.sd.crit"           "D"

As you can see, there is a lot here (some of it is simply the arguments you specified as inputs, which is nice to have in the final object in case you can’t remember what you specified).

We can estimate internal consistency using a procedure described in the Carpenter et al. (2016) manuscript and De Houwer and De Bruycker (2007) using the IATreliability() command. This returns a number of things, including $reliability which is a split-half reliability estimate:

### RELIABILITY ANALYSIS ###
IATreliability(clean)$reliability

## [1] 0.8058219

We see this IAT is estimated at .80, which is great for an IAT.

The method above is somewhat sophisticated, involving sorting trials into similar groups, then taking alternating trials, scoring the IAT separately for each half, correlating them, and using a split-half correction. Please see the De Houwer and De Bruycker (2007) paper for more information. One advantage to this method is that it analyzes the reliability of the IAT D-score. In other words, it is actually scoring the IAT. A variant of Cronbach’s alpha can also be used, which simply lines up pairs of trials (1st trial, 2nd trial, 3rd trial) from the incompatible and compatible blocks, takes the difference, and uses those differencde scores in Conbach’s alpha (see Schnabel, Asendorpf, & Greenwald, 2008). We have built this into our tool as well.

IATalpha(clean)$alpha.total

## Some items ( V2 V3 V4 V5 V7 V8 V9 V10 V14 V15 V16 V17 V21 V34 V37 ) were negatively correlated with the total scale and 
## probably should be reversed.  
## To do this, run the function again with the 'check.keys=TRUE' optionSome items ( V1.1 V12.1 V26 V27 V33 V39 ) were negatively correlated with the total scale and 
## probably should be reversed.  
## To do this, run the function again with the 'check.keys=TRUE' option

##  raw_alpha
##   0.822489

We see here using alpha that we have a score of .82. This is very similar to the split-half estimate (see our paper for other examples; they tend to produce highly similar results).

Next, we can examine the scores. The IAT scores are stored as $D. It is common to put them back into one’s datafile, but they can also be saved and exported to other software (e.g., SPSS; they will line up with the rows of the source datafile.) A positive score indicates one had a preference for the compatible block:

# place back into dat
dat$D <- clean$D

# test for IAT effect
mean(clean$D, na.rm=T)

## [1] 0.6137453

sd(clean$D, na.rm=T)

## [1] 0.3622714

t.test(clean$D)

## 
##  One Sample t-test
## 
## data:  clean$D
## t = 23.229, df = 187, p-value < 2.2e-16
## alternative hypothesis: true mean is not equal to 0
## 95 percent confidence interval:
##  0.5616230 0.6658675
## sample estimates:
## mean of x 
## 0.6137453

#cohen d
mean(clean$D, na.rm=T) / sd(clean$D, na.rm=T)

## [1] 1.694159

Here we see that the mean IAT score was M = 0.61, SD = 0.36, t(187) = 23.23, p < .001, 95% CI [0.56, 0.67], d = 1.69. This represents a rather large implicit preference for flowers over insects.

There’s much we can do at this point. For example, we could make a density plot, which shows us that the distribution is fairly symmetrical but centered well above zero (indicating that the ‘compatible’ block was indeed easier for participants).

library(ggplot2)

## Registered S3 methods overwritten by 'ggplot2':
##   method         from 
##   [.quosures     rlang
##   c.quosures     rlang
##   print.quosures rlang

## 
## Attaching package: 'ggplot2'

## The following objects are masked from 'package:psych':
## 
##     %+%, alpha

ggplot(dat, aes(x=D))+
  geom_density(color="black", fill="light blue")+
  theme_light()

## Warning: Removed 13 rows containing non-finite values (stat_density).

At this point, these responses could be exported to excel with a command such as write.csv() and pasted into another program such as SPSS (NOTE: user may need to delete NA text in missing responses prior to pasting into SPSS):

write.csv(clean$D, "iatOUTPUT.csv")

At this point, these D-scores can be correlated with other measures or otherwise analyzed. If uses wish to report the block means by participant, these can be found as well:

### RT DESCRIPTIVES BY BLOCK
mean(clean$clean.means.crit1, na.rm=T)

## [1] 882.2707

mean(clean$clean.means.crit2, na.rm=T)

## [1] 1065.307

mean(clean$clean.means.prac1, na.rm=T)

## [1] 899.6229

mean(clean$clean.means.prac2, na.rm=T)

## [1] 1165.644

sd(clean$clean.means.crit1, na.rm=T)

## [1] 230.9385

sd(clean$clean.means.crit2, na.rm=T)

## [1] 253.1042

sd(clean$clean.means.prac1, na.rm=T)

## [1] 221.7494

sd(clean$clean.means.prac2, na.rm=T)

## [1] 293.3292

License

The iatgen R package (and associated Shiny App) is licensed only for non-commercial (e.g., academic) use under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). The tool was created with the intent of making the IAT accessible to academic researchers who use Qualtrics for online research.

No warranty is offered and we assume no liability of any kind for any consequences that may result from using iatgen. This tool can be modified and distributed with attribution to us, but cannot be used for commercial purposes. More details are given in the full text of the license.

Although we believe the IAT can be validly run via Qualtrics (e.g., as set up via iatgen) and the use of Qualtrics as an IAT tool has been validated by Carpenter et al. (2018), this procedure and its code is not provided or endorsed by the IAT’s creators, and all code for this project was generated by iatgen’s creators. The official IAT sofware remains any software endorsed by the IAT’s creators. We hold no copyright to the IAT itself. We are extremely grateful to the IAT’s creators, especially Tony Greenwald, for inspiring a cohort of young scientists such as ourselves to study implicit biases and understand why people do, think, and feel what they do.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Authors

The iatgen package was built and maintained by Tom Carpenter (tcarpenter@spu.edu), Michal Kouril, Ruth Pogacar, and Chris Pullig. An early prototype of the HTML and JavaScript were built by Aleksandr Chakroff. Questions regarding iatgen should be directed to Tom Carpenter.

Acknowledgments

We would like to express our profound gratitude to Tony Greenwald and all other IAT scholars who have come before for inspiring our interest in this project. We also thank Jordan LaBouff and Stephen Aguilar for contributing validation data and to Naomi Isenberg for help setting up our website and user tutorials.

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