Final answer:
Harrar and Spence's 2013 research does not directly address the variables of expensiveness, heaviness, or saltiness of food. Their work typically involves how visual cues, like tableware color, can affect taste perception.
Step-by-step explanation:
Harrar and Spence (2013) conducted research on multisensory perception and its influence on the experience of taste and flavor. The variables they studied do not seem to pertain directly to the expensiveness, heaviness, or saltiness of food as stated in the options provided. Instead, their experiments often focused on aspects like how visual cues, such as color or size of tableware, might alter taste perceptions. For instance, their research includes experiments where the color of the cup influences people's perception of the taste of hot chocolate, demonstrating how visual cues can affect flavor assessment.
It is essential to consult the specific study by Harrar and Spence to determine the variables they investigated. The provided excerpts relate to different topics such as food availability and cost affecting diet, plant growth factors, experimental design involving the size of tableware, historical context of salt as a staple, nutrient density in food choices, and personality's effect on taste preferences. However, these excerpts do not directly mention the variables studied by Harrar and Spence in their 2013 research.