The psychological reality of the learned "p < .05" boundary.

The .05 boundary within Null Hypothesis Statistical Testing (NHST) "has made a lot of people very angry and been widely regarded as a bad move" (to quote Douglas Adams). Here, we move past meta-scientific arguments and ask an empirical question: What is the psychological standing of the .05 boundary for statistical significance? We find that graduate students in the psychological sciences show a boundary effect when relating p-values across .05. We propose this psychological boundary is learned through statistical training in NHST and reading a scientific literature replete with "statistical significance". Consistent with this proposal, undergraduates do not show the same sensitivity to the .05 boundary. Additionally, the size of a graduate student's boundary effect is not associated with their explicit endorsement of questionable research practices. These findings suggest that training creates distortions in initial processing of p-values, but these might be dampened through scientific processes operating over longer timescales.

Enhanced Parenteral Nutrition Is Feasible and Safe in Very Low Birth Weight Preterm Infants: A Randomized Trial.

OBJECTIVE: The objective of this study was to determine the feasibility and safety of enhanced early (PN) (early initiation of intralipids and faster advancement of glucose infusion rate) during the first week of life for very low birth weight (VLBW) preterm infants. METHODS: 90 VLBW preterm infants (<32 weeks gestational age at birth) admitted to the University of Minnesota Masonic Children's Hospital between August 2017 and June 2019 were included. Enrolled infants were stratified by gestational age-groups and randomized to either the enhanced nutrition protocol (intervention group) or the standard PN protocol (standard group). Welch's two-sample t tests were used to investigate differences in calorie and protein intake, insulin use, days of hyperglycemia, hyperbilirubinemia, and hypertriglyceridemia, and proportion of bronchopulmonary dysplasia, necrotizing enterocolitis, and death between groups. RESULTS: Intervention and standard groups were similar in baseline characteristics. The intervention group received higher weekly mean caloric intake (102.6 [SD 24.9] kcal/kg/day versus 89.7 [SD 30.2] kcal/kg/day; p = 0.001) and higher mean caloric intake on days of life 2-4 (p < 0.05 for all). Both groups received the recommended protein intake (≥4 g/kg/day). There were no significant differences in safety or feasibility outcomes between groups (all p values >0.12). CONCLUSION: Utilization of an enhanced nutrition protocol during the first week of life resulted in increased caloric intake and was feasible with no evidence of harm. Follow-up of this cohort is needed to determine if enhanced PN will result in improved growth and neurodevelopment.

Pediatric End-of-Life Care Skills Workshop: A Novel, Deliberate Practice Approach.

INTRODUCTION: Pediatric end of life (EOL) care skills are a high acuity, low occurrence skill set required by pediatric clinicians. Gaps in education and competence for this specialized care can lead to suboptimal patient care and clinician distress when caring for dying patients and their families. METHODS: A half-day workshop using a deliberate practice approach was designed by an inter-professional workgroup including bereaved parent consultants. Pediatric fellows (neonatal-perinatal medicine, critical care, hematology oncology, blood and marrow transplant) and advanced practice providers learned and practiced EOL skills in a safe simulation environment with instruction from interprofessional facilitators and standardized patients. Participant perceived competence (self-efficacy) was measured before, immediately-post, and 3 months post workshop. RESULTS: There were 28 first-time (of 34 total) participants in 4 pilot workshops. Participants reported significantly increased self-efficacy post-workshop for 6 of 9 ratings, which was sustained 3 months afterwards. Most (92%, n = 22 of 24 respondents) reported incorporating the workshop training into clinical practice at 3-month follow-up. CONCLUSIONS: With early success of the pilot workshops, future iterative work includes expanding workshops to earlier, interprofessional learners and collecting validity evidence for a competency-based performance checklist tool. A project website (https://z.umn.edu/PECS) was developed for local and collaborative efforts.

How do humans want causes to combine their effects? The role of analytically-defined causal invariance for generalizable causal knowledge.

The present paper reports two experiments (N = 232, 254) addressing the question: How do reasoners reconcile the desire to have useable (i.e., invariant) causal knowledge - knowledge that holds true when applied in new circumstances/contexts - with the reality that causes often interact with other causes present in the context? The experiments test two views of how reasoners learn and generalize potentially complex causal knowledge. Previous work has focused on reasoners' ability to learn rules (functions) describing how pre-defined candidate causes combine, potentially interactively, to produce an outcome in a domain. This empirical-function-learning view predicts that participants would generalize an acquired combination rule based on similarity to stimuli they experienced in the domain. An alternative causal-invariance view goes beyond empirical learning: it allows for the possibility that one's current representation may not yield useable causal knowledge. This view posits that the human causal-induction process incorporates invariant knowledge as an aspiration, entailing that observed deviation from causal invariance when the knowledge is applied serves as a signal for a need to revise causal knowledge: Only invariance across contexts with potentially new causal factors justifies generalization across them. The invariance view therefore predicts that reasoners would revise their representation so that they have whole causes - potentially consisting of interacting components - that do not interact with each other, even when in their relevant experience all (pre-defined) causes interact. Across both experiments, our results favor the causal-invariance view: Participants generalize their empirically learned function (which may involve interactions) to new stimuli, but switch to the analytic causal-invariance function for both old and new stimuli at the level of the whole cause, indicating that how humans want causes to combine their effects shapes the knowledge they induce.

Causal invariance as a tacit aspiration: Analytic knowledge of invariance functions.

For causal knowledge to be worth learning, it must remain valid when that knowledge is applied. Because unknown background causes are potentially present, and may vary across the learning and application contexts, extricating the strength of a candidate cause requires an assumption regarding the decomposition of the observed outcome into the unobservable influences from the candidate and from background causes. Acquiring stable, useable causal knowledge is challenging when the search space of candidate causes is large, such that the reasoner's current set of candidates may fail to include a cause that generalizes well to an application context. We have hypothesized that an indispensable navigation device that shapes our causal representations toward useable knowledge involves the concept of causal invariance - the sameness of how a cause operates to produce an effect across contexts. Here, we tested our causal invariance hypothesis by making use of the distinct mathematical functions expressing causal invariance for two outcome-variable types: continuous and binary. Our hypothesis predicts that, given identical prior domain knowledge, intuitive causal judgments should vary in accord with the causal-invariance function for a reasoner's perceived outcome-variable type. The judgments are made as if the reasoner aspires to formulate causally invariant knowledge. Our experiments involved two cue-competition paradigms: blocking and overexpectation. Results show that adult humans tacitly use the appropriate causal-invariance functions for decomposition. Our analysis offers an explanation for the apparent elusiveness of the blocking effect and the adaptiveness of intuitive causal inference to the representation-dependent reality in the mind.

Categorical Perception of p-Values.

Traditional statistics instruction emphasizes a .05 significance level for hypothesis tests. Here, we investigate the consequences of this training for researchers' mental representations of probabilities - whether .05 becomes a boundary, that is, a discontinuity of the mental number line, and alters their reasoning about p-values. Graduate students with statistical training (n = 25) viewed pairs of p-values and judged whether they were "similar" or "different." After controlling for several covariates, participants were more likely and faster to judge p-values as "different" when they crossed the .05 boundary (e.g., .046 vs. .052) compared to when they did not (e.g., .026 vs. .032). This result suggests a categorical perception-like effect for the processing of p-values. It may be a consequence of traditional statistical instruction creating a psychologically real divide between so-called statistical "significance" and "nonsignificance." Such a distortion is undesirable given modern approaches to statistical reasoning that de-emphasize dichotomizing the p-value continuum.

Dynamic mesolimbic dopamine signaling during action sequence learning and expectation violation.

Prolonged mesolimbic dopamine concentration changes have been detected during spatial navigation, but little is known about the conditions that engender this signaling profile or how it develops with learning. To address this, we monitored dopamine concentration changes in the nucleus accumbens core of rats throughout acquisition and performance of an instrumental action sequence task. Prolonged dopamine concentration changes were detected that ramped up as rats executed each action sequence and declined after earned reward collection. With learning, dopamine concentration began to rise increasingly earlier in the execution of the sequence and ultimately backpropagated away from stereotyped sequence actions, becoming only transiently elevated by the most distal and unexpected reward predictor. Action sequence-related dopamine signaling was reactivated in well-trained rats if they became disengaged in the task and in response to an unexpected change in the value, but not identity of the earned reward. Throughout training and test, dopamine signaling correlated with sequence performance. These results suggest that action sequences can engender a prolonged mode of dopamine signaling in the nucleus accumbens core and that such signaling relates to elements of the motivation underlying sequence execution and is dynamic with learning, overtraining and violations in reward expectation.