Session 1

In this session, we will focus on the steps involved in developing an experimental psychology experiment, and we will get our hands on E-Prime, using a lexical decision task as an example. Below is an outline of the key stages and concepts we’ll be implementing in E-Prime for this experiment.

Key Stages in Experimental Development

  1. Conceptualize the Core Experimental (trial) Procedure
    This is where you define the fundamental, hierarchical structure of the experiment.

  2. Elaborate the Trial Procedure
    Determine how each trial will flow and what elements will be presented.

  3. Add All Conditions and Set the Number of Trials and Sampling Strategy
    Define the independent variables, number of trials, and how trials are sampled.

  4. Add Blocks and Block Conditions
    Break the trials into blocks and set conditions for each block.

  5. Add a Practice Block
    Include a practice phase where participants can familiarize themselves with the task.

  6. Testing and Running the Program
    Ensure the experiment runs smoothly and make any necessary adjustments.

  7. Perform Basic Data Analysis
    Take a first look at the results once the data is collected to make sure everything looks fine.

Developing a Lexical Decision Task

In this session, we’ll create a lexical decision task, where participants must determine whether a string of letters is a word or a non-word. The task will consist of several trials, each with the following sequence:

  • Fixation: Displayed for 1000ms
  • Probe: Displayed for 2000ms

For each trial, the word will either be a real word (e.g., “cat”) or a non-word (e.g., “jop”). The task will require participants to press a specific key based on whether they think the displayed string is a word or non-word.

Fixed vs. Varying Properties

To understand how E-Prime works, a key concept to always keep in mind is the distinction between fixed and varying properties in an experiment: - Fixed properties: Elements like the fixation display (e.g., position, color, duration) will remain the same across trials. - Varying properties: The actual words and correct responses will change with each trial.

If we define which properties remain constant and which vary across trials when designing each event, it will be easir to understand which information goes into a procedure and what goes into a list.

Adding Complexity to the Experiment

We will also explore the following adjustments:

  • Blocks: The experiment will consist of two blocks, with a break in between.
  • Counterbalancing: To avoid response bias, responses can be counterbalanced across participants. For example:
    • Participant 1: word = “k”, non-word = “l”
    • Participant 2: word = “l”, non-word = “k”

Adding a Practice Block

Before the actual experiment, we’ll include a practice block with the following key differences: - Feedback will be provided after each trial to help participants learn the task. - Practice trials will be marked separately to exclude them from the final data analysis.

Food for thought
  • Why is it essential to define both fixed and varying properties for an experiment? Provide examples of each in the context of a Stroop task.

Below, you can find the slides from this session: