Supporting the foundation of EEG research through replication: The relationship between contralateral delay activity and visual working memory

Abstract

The current paper is a replication of Vogel and Machizawa’s 2004 study on the biomarker contralateral delay activity (CDA). The data used was gathered for #EEGManyLabs as part of their multinational replication project. Our sample was composed of 25 participants, aged 20 to 38 years. The task consisted of memory and test arrays of two, four or six different coloured squares appearing to the left and right of a central fixation cross. A cue indicated to the participants to heed either the left or right side of the screen, without moving their gaze from the central cross. A brief memory array was followed by a test array which was either identical or differed by only one coloured square. The participants then had to respond whether they detected a change or not. According to the original study, the CDA amplitude is expected to increase in conjunction with items held in visual working memory, but plateau when the memory has reached its maximum capacity, at around three to four items. Individuals with higher memory capacity are also expected to display a higher increase in CDA amplitude between set sizes. Our findings could not support the difference in CDA amplitude between set sizes, although a numerical difference did appear. While we did observe a correlation between memory capacity and CDA amplitude, the effect size was considerably less than that achieved in the original study.