2025-05-08

Introduction

  • The dataset is drawn from a human category learning experiment.

  • The dataset is available at:
    https://github.com/crossley/crit_learn_delay

  • This repository contains behavioural data from experiments investigating criterial learning under different feedback delays.

Example Trial and Basic Stimuli

How Stimuli Are Clustered Into Categories

Dataset Description

Example Data File

Data Analysis

  • Data files were read in and combined using data.table in R.

  • Each subject completed multiple problems; we computed the number of trials to reach criterion (t2c) for each problem and averaged across problems for each subject.

Histogram of Trials to Criterion

Identifying and Removing Outliers

  • We filtered out outliers with t2c >= 300.

  • Sample sizes per condition before filtering:

##          cnd     N
##       <char> <int>
## 1:     Delay    20
## 2:  Long ITI    21
## 3: Short ITI    17
  • Sample sizes per condition after filtering:
##          cnd     N
##       <fctr> <int>
## 1:     Delay    17
## 2:  Long ITI    18
## 3: Short ITI    12

Histogram of Trials to Criterion

Distribution is not normal, with positive skew.

  • Shapiro-Wilk Test for Normality
cnd W p
Delay 0.9191 0.1426
Long ITI 0.8593 0.0119
Short ITI 0.8337 0.0232
  • Normality is rejected in Long ITI and Short ITI conditions.

  • Despite this, ANOVA and t-tests are generally robust to mild violations of normality.

ANOVA Results

##        Effect DFn DFd       SSn    SSd          F            p p<.05       ges
## 1 (Intercept)   1  44 698082.27 106086 289.535175 5.673951e-21     * 0.8680799
## 2         cnd   2  44  26365.99 106086   5.467751 7.571651e-03     * 0.1990608
  • Significant main effect of condition on t2c.

  • Proceeded with pairwise t-tests to interpret effects.

Post-hoc t-tests

Comparison t_stat p_val
Delay vs Long ITI 3.0986 0.0042
Delay vs Short ITI 2.3223 0.0287
Long ITI vs Short ITI -0.3208 0.7516
  • Delay condition resulted in significantly more trials than either Long or Short ITI.

  • No significant difference between Long ITI and Short ITI.

Bar Plot of Group Means

  • Clear visual separation of Delay condition from the other two.

  • Error bars represent standard error of the mean (SEM).

Summary

  • Longer feedback delays led to slower learning (higher trials-to-criterion).

  • Results support the hypothesis that delay disrupts criterial learning.

  • Caution is warranted in interpreting results due to non-normality and outliers.