A systematic review of protocol studies on conceptual design cognition: design as search and exploration

This paper reports findings from the first systematic review of protocol studies focusing specifically on conceptual design cognition, aiming to answer the following research question: What is our current understanding of the cognitive processes involved in conceptual design tasks carried out by individual designers? We reviewed 47 studies on architectural design, engineering design, and product design engineering. This paper reports 24 cognitive processes investigated in a subset of 33 studies aligning with two viewpoints on the nature of designing: (V1) design as search (10 processes, 41.7%); and (V2) design as exploration (14 processes, 58.3%). Studies on search focused on solution search and problem structuring, considered to involve: long term memory retrieval; working memory; and a range of operators. Reasoning processes are also examined. Studies on exploration investigated: (i) co-evolutionary design; (ii) visual reasoning processes; (iii) cognitive actions; and (iv) unexpected discovery and situated requirements invention. Overall, considerable conceptual and terminological differences were observed among the studies. Nonetheless, a common focus on memory, semantic, associative, visual perceptual, and mental imagery processes was observed to an extent. We suggest three challenges for future research to advance the field: (i) developing general models and theories; (ii) testing protocol study findings using objective methods conducive to larger samples; and (iii) developing a shared ontology of cognitive processes in conceptual design.