When monitoring attentional parameters for gradual changes over the course of an experiment, we strive for quick and precise estimations in small time intervals. The long-standing question on how to reduce the number of necessary trials for a sufficiently accurate parameter estimation, driven by economic reasons or by the desire to design the experiment to be less taxing for participants, has produced quite a few adaptive methods that involve reducing the probed stimulus levels of individuals in a task and hence, increasing the overall task difficulty. Progressively narrowing the set of stimulus levels, e.g., by removing higher stimulus onset asynchrony levels from a temporal-order judgment task, leads to accurate parameters estimates if inter-trial effects due to stimulus-level changes are assumed to be non-existent or non-confounding. There are findings about higher arousal with an accompanied better performance when participants encounter tasks with higher difficulty. These effects may not matter for finding absolute perceptual thresholds. However, in experiments where the psychophysical task is used to measure the effect of an intervention which itself may be difficult to process, performance changes due to higher task difficulty of the adaptive measure is a confounding variable. With a model based on the Theory of Visual Attention (TVA), we evaluate how increased difficulty of the spatial temporal-order judgment task affects visual attentional capacity and its distribution. Considering the results, we discuss the practical implications for experiments in which a limited number of trials are available for probing.