PsySimulate: Simulate psychophysical data

In MixedPsy: Statistical Tools for the Analysis of Psychophysical Data

Simulate psychophysical data

Description

The function simulates data from a typical psychophysics experiment using a 2-alternative forced choice task and the method of constant stimuli. For each simulated participant, the function returns the following information: individual slope and intercept coefficients, based on the fixed and random effects parameters provided as input; summary of the simulated binomial response across a range of intensity levels within a specified stimulus range; individual lapse and guess rates, if applicable.

Usage

PsySimulate(
  fixeff = c(-7, 0.0875),
  raneff = c(2.4, -0.002, 2e-06),
  nsubjects = 8,
  ntrials = 40,
  nintervals = 9,
  xint = c(40, 120),
  constant = T,
  lapse = FALSE,
  guess = FALSE,
  lapse_range = c(0, 0.05),
  guess_range = c(0, 0.05)
)

Arguments

fixeff	Numeric array of fixed effects. The first item is the intercept, the second element is the slope.
raneff	Numeric array of random effects. The first element is the intercept, the second is the covariance, the third is the slope variance.
nsubjects	Integer. Number of subjects to simulate. Default is 8.
ntrials	Integer. Number of trials for each stimulus level. Default is 40.
nintervals	Integer. Number of stimulus levels. Default is 9.
xint	Numeric array specifying the range of stimulus intensity. Default is c(40,120)
constant	Logical. If TRUE (defualt), stimulus levels are evenly spaced across 'xint'. If FALSE, stimulus levels are randomly generated within the interval.
lapse	Logical or numeric. If FALSE (default), no lapse rate is applied. If TRUE, a random lapse rate is drawn from 'lapse_range'. If a numeric value is provided, all subjects will have the same lapse rate.
guess	Logical or numeric. If FALSE (default), no guessing rate is applied. If TRUE, a random guessing rate is drawn from 'guess_range'. If a numeric value is provided, all subjects will have the same guess rate.
lapse_range	Numeric array defining the minimum and maximum lapse rates when 'lapse = TRUE'. Default is c(0, 0.05).
guess_range	Numeric array defining the minimum and maximum guessing rates when 'guess = TRUE'. Default is c(0.05, 0.10).

Value

A data frame containing simulated psychophysical data with the following columns:

• Subject - Subject identifier.

• X - Stimulus intensity levels.

• Intercept - Individual intercept values.

• Slope - Individual slope values.

• Gamma (optional) - Guess rate, included if 'guess' is not FALSE.

• Lambda (optional) - Lapse rate, included if 'lapse' is not FALSE.

• Longer - Number of "Longer" responses at each stimulus level.

• Total - Total number of trials per stimulus level.

See Also

PsychShape for plotting a psychometric function given PSE and JND. simul_data for a dataset simulated with the function.

Examples

datafr.S1 <- PsySimulate(fixeff = c(0, 1), xint = c(-5,5), 
nsubject = 1, ntrials = 60, nintervals = 10, constant = FALSE)

simul_data <- PsySimulate(ntrials = 160, nsubjects = 10, guess = TRUE, lapse = TRUE)

MixedPsy documentation built on April 4, 2025, 3:50 a.m.