When Objects Disintegrate: Young Children Do Not Bind Features in Visual Working Memory

When Objects Disintegrate: Young Children Do Not Bind Features in Visual Working Memory Vanessa R. Simmering (simmering@wisc.edu) 1 , Jeffrey S. Johnson (jsjohnson3@wisc.edu) 2 Department of Psychology, 1202 W. Johnson Street; 2 Department of Psychiatry, 6001 Research Park Blvd. University of Wisconsin – Madison, Madison, WI 53706 USA Chelsey M. Patterson (chelsey-patterson@uiowa.edu) 3 , John P. Spencer (john-spencer@uiowa.edu) 3,4 Department of Psychology, E11 Seashore Hall; 4 Delta Center University of Iowa, Iowa City, IA 52242 USA that 4-year-olds, but not 5-year-olds, have difficulty remembering object locations relative to object configurations (Nardini, Burgess, Breckinridge, & Atkinson, 2006). Here, we suggest that these results are linked and test whether 4-year-olds show a binding-specific deficit consistent with their inability to anchor features to object configurations. Thus, 4-year-olds might remember that a duck, ball, and car were present in a scene and, further, that the objects were red, blue, and yellow, but not remember that the duck was blue, the ball was red, and the car was yellow. Abstract Remembering object identities requires ‘binding’ visual features together in working memory to form integrated object representations. Research with adults suggests that such feature binding is achieved through space: features at a given spatial location are ‘bound’ to create integrated objects that are anchored to a spatial map of the object layout. Critically, 4-year-old children do not form such spatial maps, whereas 5-year-old children do. This suggests that 4-year- olds might have difficulty binding features together in visual working memory. We tested 4- and 5-year-old children and adults in a change detection task, and found that 4-year-olds showed a binding-specific deficit. Thus, the ability to represent integrated objects in visual working memory is a relatively late developmental achievement. We suggest that before 5 years of age children’s object representations are primarily mediated through visual long-term memory. Feature Binding in Visual Working Memory The past decade has seen considerable debate in the VWM literature over whether feature binding presents a problem in vision (for reviews, see Luck & Beach, 1998; Roskies, 1999; Treisman, 1996). Evidence suggests that object properties such as color, form, and size are coded in a distributed manner across different neural populations in the ventral pathway (Tootell, Dale, Sereno, & Malach, 1998). As information passes through this pathway, there is an increase in the complexity of the features coded (Desimone, Albright, Gross, & Bruce, 1984) and receptive field sizes, with a decrease in the spatial resolution of receptive fields for individual neurons (Gross, Rocha-Miranda, & Bender, 1972). Consequently, when multiple objects are present in a scene, it may be difficult to determine which features belong together as VWM representations. Consistent with this, adults sometimes report illusory conjunctions, correctly reporting that a target feature was present but mis-binding that feature with the color of a nearby distracter (Ashby, Prinzmetal, Ivry, & Maddox, 1996). 1 Although the debate over the binding “problem” is far from resolved (e.g., Garson, 2001), several behavioral studies with adults have shown that feature binding can present a challenge in working memory tasks (Allen et al., 2006; J.S. Johnson, Hollingworth, & Luck, 2008; Wheeler & Treisman, 2002). Several theories suggest that features may be bound by integrating spatial and non-spatial visual features (J.S. Johnson, Spencer, & Schoner, 2008). According to feature integration theory (Treisman & Gelade, 1980), for instance, object features are bound Keywords: visual working memory; feature binding; spatial memory; cognitive development Visual Working Memory Human adults can quickly form a mental map of which objects are where in a local workspace. Adults form working memory representations of 3-4 objects in a few hundred milliseconds with enough detail to detect changes in those objects a second later, even when the objects are composed of multiple simple features such as color, orientation, and size (e.g., Luck & Vogel, 1997). Moreover, given just 20 seconds to scan the surrounds, adults can detect a subtle change in the features of an object in a scene as much as 24 hours later after viewing more than 400 objects (Hollingworth, 2005). There are, of course, limitations to humans’ visuo-spatial abilities (e.g., Pashler, 1992; Rensink, 2000), but these examples highlight the fast, flexible visual working memory (VWM) system that underlies adults’ interactions with objects. The present report examines the developmental origin of this ability. Can young children quickly form representations of which objects are where with sufficient detail to detect changes in those objects a second later? This may not be the case. As we review below, research suggests that visual features such as shape and color are ‘bound’ in working memory by virtue of their shared spatial location within the configuration of objects in a scene (e.g., Hollingworth, 2007; J.S. Johnson, Spencer, & Schoner, 2008; Treisman & Gelade, 1980). Evidence further suggests Although these studies did not use working memory paradigms, it is plausible that the perceptual mis-binding of features they show would affect working memory representations.