Conceptual combination is a cognitive process that produces complex concepts (e.g., adjective-noun pairs) from simple concepts. The Selective Modification Model (SMM; Smith, Osherson, Rips, & Keane, 1988) postulates that simple adjective-noun combinations (e.g., red apple) are understood by the modifier red selecting the colour attribute of the head noun apple. Theories of conceptual combination have not extended to fulfill our understanding of how complex adjective-noun pairs (e.g., empty dream) are processed. This exploratory study had two main objectives: to determine which semantic variables best captured the processing of complex adjective-noun pairs and to examine the semantic effects of conceptual combination to extend current theories. Adjective-noun combinations were manipulated based on subjective ratings (i.e., concreteness and plausibility; see the preliminary study) or objective measures (i.e., age of acquisition and semantic distance) and compared. Two hundred and ninety-three participants were randomly assigned to complete one of three computerized tasks that differentially engaged semantic processing from shallow to deep, including the non-pronounceable double lexical decision task (Experiment 1), the pronounceable double lexical decision task (Experiment 2), and the meaningfulness task (Experiment 3). Across all tasks, the subjective model outperformed the objective model in reaction time and accuracy analyses. Adjective-noun processing was facilitated by concrete, early acquired head nouns, as well as adjective-noun pairs that were rated as plausible and situated close in semantic space. Interestingly, adjectives paired with abstract head nouns were difficult to process across tasks regardless of how plausible the pair was. In conclusion, semantic variables rated by participants are valuable and may better capture how the mental lexicon is organized and accessed, and further research should pursue innovative ways of examining how abstract head nouns are processed to incorporate into existing theories
