RESEARCH REPORT Semantic and Functional Relationships Among Objects Increase the Capacity of Visual Working Memory Ryan E. O’Donnell, Andrew Clement, and James R. Brockmole University of Notre Dame Visual working memory (VWM) has a limited capacity of approximately 3– 4 visual objects. Current theories of VWM propose that a limited pool of resources can be flexibly allocated to objects, allowing them to be represented at varying levels of precision. Factors that influence the allocation of these resources, such as the complexity and perceptual grouping of objects, can thus affect the capacity of VWM. We sought to identify whether semantic and functional relationships between objects could influence the grouping of objects, thereby increasing the functional capacity of VWM. Observers viewed arrays of 8 to-be-remembered objects arranged into 4 pairs. We manipulated both the semantic associ- ation and functional interaction between the objects, then probed participants’ memory for the arrays. When objects were semantically related, participants’ memory for the arrays improved. Participants’ memory further improved when semantically related objects were positioned to interact with each other. However, when we increased the spacing between the objects in each pair, the benefits of functional but not semantic relatedness were eliminated. These findings suggest that action-relevant properties of objects can increase the functional capacity of VWM, but only when objects are positioned to directly interact with each other. Keywords: visual working memory, working memory capacity, action, functional interactions, object affordances Visual working memory (VWM) is a limited capacity resource that allows observers to temporarily store and mentally manipulate up to 3– 4 visual objects (Cowan, 2001; Luck & Vogel, 1997). Understanding the factors that underlie this limit has been an important area of research over the past two decades. The first theories to account for the capacity of VWM are broadly referred to as “slot theories.” According to these theories, VWM contains a fixed number of independent storage slots, each of which can hold a single object (e.g., Awh, Barton, & Vogel, 2007; Gajewski & Brockmole, 2006; Luck & Vogel, 1997; Zhang & Luck, 2008). Once the available slots are full, additional objects are unable to enter VWM, resulting in memory failures. However, a growing body of evidence suggests that slot theories are too rigid in their conception of VWM capacity, and a newer set of theories referred to as “resource theories” have emerged (see Ma, Husain, & Bays, 2014, for a review). Although multiple versions have been suggested, resource the- ories as a class propose that VWM capacity arises from a limited pool of resources that can be flexibly allocated to objects (e.g., Alvarez & Cavanagh, 2004; Franconeri, Alvarez, & Cavanagh, 2013; Gorgoraptis, Catalao, Bays, & Husain, 2011; van den Berg, Shin, Chou, George, & Ma, 2012; Wilken & Ma, 2004). As more resources are allocated to an object, that object can be better represented in VWM. However, as the number of to-be- remembered objects increases, the resources that can be allocated to each one declines, along with the quality with which they can be represented. Thus, according to this view, memory failures occur not because some objects are prevented from entering VWM, but because not all objects can be sufficiently represented to complete a given task (e.g., Schneegans & Bays, 2016). As a result, these theories suggest that the capacity of VWM is not only influenced by the number of objects in a display, but also by other factors that modulate how resources can be allocated to objects. For example, as objects become more visually complex, fewer of them can be remembered, because more complex objects require more re- sources to be represented (Alvarez & Cavanagh, 2004; see also Wheeler & Treisman, 2002; Xu, 2002). Thus, although VWM has a limited capacity, an emerging view is that this limit is not fixed. Instead, the functional capacity of VWM appears to be flexible based on how resources are used to encode and store visual information. However, the factors that influence the capacity of VWM are not fully understood, in part because the methods that have been used to assess VWM capacity have been rather restricted in their range. The most common This article was published Online First April 12, 2018. Ryan E. O’Donnell, Andrew Clement, and James R. Brockmole, De- partment of Psychology, University of Notre Dame. Ryan E. O’Donnell now at Department of Psychology, Pennsylvania State University. This research was conducted as part of a senior thesis by Ryan E. O’Donnell at the University of Notre Dame. Correspondence concerning this article should be addressed to James R. Brockmole, Department of Psychology, University of Notre Dame, Notre Dame, IN 46556. E-mail: james.brockmole@nd.edu This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Journal of Experimental Psychology: Learning, Memory, and Cognition © 2018 American Psychological Association 2018, Vol. 44, No. 7, 1151–1158 0278-7393/18/$12.00 http://dx.doi.org/10.1037/xlm0000508 1151