Pre-crastination and procrastination effects occur in a reach-to-grasp task

Physical effort precrastination determines preference in an isometric task

How the brain decides when to invest effort is a central question in neuroscience. When asked to walk a mile to a destination, would you choose a path with a hill at the beginning or the end? The traditional view of effort suggests we should be indifferent-all joules are equal so long as it does not interfere with accomplishing the goal. Yet, when total joules are equal across movement decisions, the brain's sensitivity to the temporal profile of effort investment remains poorly understood. Here, we sought to parse the interaction of time and physical effort by comparing subjective preferences in an isometric arm-pushing task that varied the duration and timing of high and low effort. Subjects were presented with a series of two-alternative forced choices, where they chose the force profile they would rather complete. Subjects preferred earlier physical effort (i.e., to precrastinate) but were idiosyncratic about preference for task timing. A model of subjective utility that includes physical effort costs, task costs, and independent temporal sensitivity factors described subject preferences best. Interestingly, deliberation time and response vigor covary with the same subjective utility model for preference, suggesting a utility that underlies both decision making and motor control. These results suggest physical effort costs are temporally sensitive, with earlier investment of effort preferred to later investment, and that the representation of effort is based on not only the total energy required but also when it is required to invest that energy.NEW & NOTEWORTHY We use a novel paradigm that differentiates physical effort costs, task costs, and time, where subjects choose between isometric arm-pushing tasks. Subjects prefer high physical effort earlier than later. They also decide faster and respond more vigorously the greater their preference. We find a generalizable subjective utility model that includes independent time-sensitivity of physical effort and task costs. Together, we demonstrate that subjective effort includes not only the total effort invested but also its timing.

Pre-crastination across physical and cognitive tasks

Pre-crastination refers to the tendency to begin a task as soon as possible, even at the cost of additional effort. This phenomenon is consistently observed in tasks in which participants are asked to select one of two buckets to carry to a target. Surprisingly, on a high proportion of trials participants choose the bucket that is closer to them (and further from the target) as opposed to the bucket that is further from them (and closer to the target). In other words, participants tend to complete the task of picking up a bucket as soon as possible, even when this requires additional physical effort. The purpose of the current experiment was to test whether an individual's tendency to pre-crastinate is stable across tasks. Participants performed a physical load task where they selected one of two buckets to carry to a target. The same participants performed a cognitive load task where they picked up number strings at one of the two bucket locations and mentally carried the number string to a target. We found that participants pre-crastinated in both tasks and this tendency was reduced as task difficulty increased. Importantly, we found a significant association between an individual's tendency to pre-crastinate in the physical load task and their tendency to pre-crastinate in the cognitive load task. Thus, an individual's tendency to pre-crastinate is consistent across tasks and suggests that this is a stable characteristic of how individuals choose to order tasks.

Precrastination and Time Perspective: Evidence from Intertemporal Decision-Making

Although procrastination has been extensively studied, precrastination remains an unsolved puzzle. Precrastination is the tendency to start tasks as soon as possible, even at the cost of extra effort. Using the near bucket paradigm with 81 undergraduate students, this study examined the relationship between precrastination and time perspective, proactive personality, and subjects' differential performance in intertemporal decision-making. The results confirmed the cognitive-load-reduction (CLEAR) hypothesis. Precrastination was found to be positively predicted by the future time dimension of time perspective and negatively predicted by proactive personality. In addition, there is a significant positive correlation between precrastination and delay discounting of intertemporal decision-making, which exists only for the loss situation.

Carrying groceries: More items in early trips than in later trips or the reverse? Implications for pre-crastination

Returning home from the grocery store with a car full of groceries requires decisions about how many bags to carry when. If the decisions exemplify procrastination, people should carry more bags per trip in late trips than in early trips (putting the hard work off until later), but if the decisions exemplify the recently discovered phenomenon of pre-crastination (Rosenbaum et al. in Psychol Sci 25: 1487-1496, 2014), people should carry more bags per trip in early trips than in late trips (doing the hard work early). To distinguish between these possibilities, we asked university students to carry 5 or 11 dodgeballs from one bin to another 4, 8, 12, or 16 feet away in as many trips as they wished. A random half of the subjects did the tasks with an additional requirement to memorize and then recall 7 digits after carrying all the balls from the home to the target bin. Consistent with pre-crastination, participants carried the most balls per trip in early trips, and consistent with the hypothesis that pre-crastination relates to memory load, the number of balls carried per trip was affected by the presence of a memory load. The results add to the growing evidence for the generality of pre-crastination.

Precrastination and individual differences in working memory capacity

When ordering tasks, people tend to first perform the task that can be started or completed sooner (precrastination) even if it requires more physical effort. Evidence from transport tasks suggests that precrastination can reduce cognitive effort and will likely not occur if it increases cognitive effort. However, some individuals precrastinate even when it increases cognitive effort. We examined whether individual differences in working memory capacity (WMC) influence this suboptimal choice. Participants retrieved two cups of water along a corridor, in the order of their choosing. We measured the frequency of choosing the close cup first (precrastination) while varying water levels in each cup (attention demand) located at different distances. Results showed that the tendency to select the far cup first (avoid precrastination) increases when the close cup is full (high attention demand) vs. not full (low attention demand). Post-hoc results showed high (vs. low) WMC individuals more frequently bypass decisions with relatively higher costs of cognitive effort, avoiding precrastination when the attentional demand of carrying the close (vs. far) cup is relatively high (close-cup full and far-cup half full), but not when it is relatively low (far-cup full). However, there was no evidence that WMC could explain why some individuals always precrastinated, at costs of cognitive effort. Instead, individuals who always precrastinated reported automatic behavior, and those who avoided precrastinating reported decisions of efficiency. Learning, the relationship between precrastination and tendencies to enjoy/engage in thinking or procrastinate, and evidence that precrastination required more cognitive effort in our task, are discussed.

Implicit task switching in Parkinson's disease is preserved when on medication

People with Parkinson's disease have been shown to have difficulty switching between movement plans. In the great majority of studies, the need to switch between tasks was made explicitly. Here, we tested whether people with Parkinson's disease, taking their normal medication, have difficulty switching between implicitly specified tasks. We further examined whether this switch is performed predictively or reactively. Twenty five people with Parkinson's disease continuously increased or decreased the frequency of their arm movements, inducing an abrupt-but unaware-switch between rhythmic movements (at high frequencies) and discrete movements (at low frequencies). We tested whether that precipitous change was performed reactively or predictively. We found that 56% of participants predictively switched between the two movement types. The ability of people with Parkinson's disease, taking their regular medication, to predictively control their movements on implicit tasks is thus preserved.

Task order choices in cognitive and perceptual-motor tasks: The cognitive-load-reduction (CLEAR) hypothesis

A core question in the study of the dynamics of cognition is how tasks are ordered. Given two tasks, neither of which is prerequisite for the other and neither of which brings a clearly greater reward, which task will be done first? Few studies have addressed this question, though recent work has suggested one possible answer, which we here call the cognitive-load-reduction (CLEAR) hypothesis. According to the CLEAR hypothesis, there is a strong drive to reduce cognitive load (to "clear one's mind"). Given two tasks, one of which is more cognitively demanding than the other, the more cognitively demanding task will tend to be done first. We tested this prediction using a novel method inviting participants to freely choose when to perform each of c = 5, 10, or 15 items per category in item-generation tasks relative to b = 10 box-moving tasks. The box-moving tasks were cognitively undemanding relative to the item generation tasks, whose cognitive difficulty presumably grew with c. A full half of our n = 122 participants chose to complete all of the c tasks before performing any of the b tasks, and most other participants chose to complete a majority of the c tasks before any of the b tasks. This result is consistent with the CLEAR hypothesis. Speed on the box-moving task decreased the later the category-generation task was completed, supporting another CLEAR prediction. The general method used here provides direction for future work on task order choices in cognitive and perceptual-motor tasks.