Short-term memory capacity is dependent on perceived complexity, and not visual complexity per se

Visual complexity of an object can vary in different degrees, and if we have a limited short-term memory capacity (e.g. Cowan, 2001), how does memory deal with objects of high visual complexity? While early studies demonstrated that visual complexity increase the load on both processing time and memory capacity (Alvarez & Cavanagh 2004), later studies indicate that memory capacity is highly influenced by stimulus specific expertise (Sørensen, & Kyllingsbæk, 2012). Nevertheless, complexity can be divided into two types based on either visual elements or familiarity. The current aim is to examine the relationship between the visual complexity and what we term the perceived complexity. In an experiment we used Chinese characters (radicals) divided into four groups based on visual complexity or stroke count (high vs low) and perceived complexity or word frequency (high vs low). We examined this using a whole report paradigm (Sperling, 1960) with varying exposure rates and modeled the results according to the Theory of Visual Attention (Bundesen, 1990). This procedure allows us to isolate specific attentional components and the results reveal that for experienced observers differences in processing speed and memory capacity is driven solely by the perceived complexity of an object.