mpt (version 1.0-0)

valence: World Valence and Source Memory for Vertical Position

Description

Sixty-four participants studied words with positive, negative, or neutral valence displayed at the top or bottom part of a computer screen. Later, these words were presented intermixed with new words, and participants had to classify them as "top," "bottom," or "new." It was of interest if memory is improved in congruent trials, in which word valence and vertical position match (positive-top, negative-bottom), as opposed to incongruent trials.

Usage

data(valence)

Format

A data frame consisting of five components:

id

factor. Participant ID.

gender

factor. Participant gender.

age

participant age.

condition

factor. In congruent trials, positive words were presented at the top, negative words at the bottom, and vice versa for incongruent trials.

y

a matrix of aggregate response frequencies per participant and condition. The column names indicate each of nine response categories, for example, top.bottom means that words were presented at the top, but participant responded "bottom."

See Also

mpt.

Examples

data(valence)

## Fit source-monitoring model to subsets of data
spec <- mptspec("SourceMon", .restr=list(d1=d, d2=d))
names(spec$prob) <- colnames(valence$y)

mpt(spec, valence[valence$condition == "congruent" &
                  valence$gender == "female", "y"])
mpt(spec, valence[valence$condition == "incongruent" &
                  valence$gender == "female", "y"])

## Test the congruency effect
val.agg <- aggregate(y ~ gender + condition, valence, sum)
y <- as.vector(t(val.agg[, -(1:2)]))

spec <- mptspec("SourceMon", .replicates=4,
                .restr=list(d11=d1, d21=d1, d12=d2, d22=d2,
                            d13=d3, d23=d3, d14=d4, d24=d4))
m1 <- mpt(spec, y)
m2 <- mpt(update(spec, .restr=list(d1=d.f, d3=d.f, d2=d.m, d4=d.m)), y)
anova(m2, m1)  # better discrimination in congruent trials

## Plot parameter estimates
mat <- matrix(coef(m1), 5)
rownames(mat) <- c("D1", "d",  "g",  "b",  "D2")
mat <- mat[c("D1", "D2", "d", "b", "g"), ]
matplot(mat, type="b", axes=FALSE, ylab="MPT model parameter estimate",
        main="Word valence and source monitoring", ylim=0:1, pch=1:4)
axis(1, 1:5, rownames(mat)); axis(2)
legend("bottomleft", c("female, congruent", "male, congruent",
       "female, incongruent", "male, incongruent"), pch=1:4, bty="n")