Does using both visual and verbal working memory increase effective capacity compared with using only one?

The closest direct test found no advantage from using both

The most relevant evidence comes from a study of episodic future thinking, where people recalled past events or imagined future ones while also doing either a visual or a verbal 2-back task. A 2-back task means holding an item in mind and updating it as new items arrive, so it occupies working memory. Performance under visual and verbal loads was similar, which the authors interpret as overall working-memory capacity contributing to the task rather than one modality being specially recruited [2].

That similarity is the key point for the question. If visual and verbal working memory were separate pools that could be combined, you would expect the two load types to interfere differently, or a dual-task condition to leave more room than a single load. Instead, the loads behaved alike, which is consistent with a shared capacity being the limiting factor [2]. The study measured performance under load, not a direct count of how many items could be held, so it speaks to interference rather than to a literal capacity number.

Visual and verbal capacity can still matter differently for different tasks

Similar load effects do not mean the two modalities are interchangeable everywhere. In a numerosity comparison task, people judged which of two dot arrays had more dots while the arrays varied in dot size, total area, and density. Those who scored low on visuo-spatial working memory were more swayed by these non-numerical visual features than those who scored high, while verbal working-memory scores made no difference between groups [1].

That pattern fits the idea that the visual task leans on visual working memory specifically. It does not show that adding verbal working memory on top would help; it shows that the relevant modality matters for how well people ignore distracting visual information [1]. In a sports decision-making study, higher verbal working memory was linked to more accurate decisions when opponents' action preferences were given verbally, and higher visuo-spatial and verbal capacity were both linked to slower responses. The authors concluded that working-memory capacity may play only a subordinate role in this kind of fast decision [4].

So the modality can shape which information gets used, but the evidence does not show a combined visual-plus-verbal store that expands what a person can hold. The differences appear as task-specific strengths, not as extra capacity from running both at once [1][4].

What this means if you are trying to stretch your working memory

If the goal is to hold more in mind by engaging both visual and verbal channels, these results offer little support. The direct comparison found visual and verbal loads equally demanding [2], and the studies that separate the modalities show them doing different jobs rather than adding together [1][4]. A reasonable reading is that working memory is limited by a shared resource, and switching modality does not create a second, independent reserve.

There is one caveat about scope. The direct test involved remembering past and imagined events, not a pure span task, so its conclusion is about how loads interfere during complex thinking rather than about maximum item counts [2]. The other studies measured individual differences in capacity, not the effect of using two modalities at once [1][4]. None of the evidence rules out that some tasks recruit visual and verbal codes in ways that feel easier, but none shows that this raises effective capacity.

The evidence base is thin on the exact comparison

Only one of these studies sets up single- versus dual-task conditions that speak to the question, and it did so in a future-thinking paradigm rather than a direct capacity test [2]. The others measured visual and verbal working memory separately and related them to task performance, so they can tell us that the modalities differ in relevance but not whether combining them increases capacity [1][4].

Two further studies in this set do not address the comparison at all. One found poorer verbal working memory, but not visual working memory, in people with a history of mild traumatic brain injury [3]. Another reported that a brain-stimulation technique improved visual-verbal working memory in a small group of patients with ADHD [5]. Neither compares using both modalities against using one, so they leave the central question open. On current evidence, the honest answer is that combining visual and verbal working memory has not been shown to increase effective capacity.

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