Final answer:
In Lavie's theory, perceptual load is the construct influenced by task difficulty, as it encompasses how much information a task requires to be processed and its demand on cognitive resources.
Step-by-step explanation:
In Lavie's account of attention, the construct that is a function of task difficulty is c. perceptual load. Perceptual load refers to the amount of information that a given task requires an individual to process. Therefore, as the difficulty of a task increases, so does the perceptual load, demanding more cognitive resources from an individual's attentional capacity to process the incoming stimuli.
The basic premise behind Lavie's theory is that our attentional resources are limited. When a task is not demanding enough to use all of the available attentional resources (low perceptual load), we are more susceptible to distractions. If a task is highly demanding (high perceptual load), it consumes more attentional resources, making it harder for distractions to be processed. Thus, perceptual load is a crucial factor in determining how easily we can be distracted from a given task.