Credit assignment in hierarchical option transfer.

Humans have the exceptional ability to efficiently structure past knowledge during learning to enable fast generalization. Xia and Collins (2021) evaluated this ability in a hierarchically structured, sequential decision-making task, where participants could build "options" (strategy "chunks") at multiple levels of temporal and state abstraction. A quantitative model, the Option Model, captured the transfer effects observed in human participants, suggesting that humans create and compose hierarchical options and use them to explore novel contexts. However, it is not well understood how learning in a new context is attributed to new and old options (i.e., the credit assignment problem). In a new context with new contingencies, where participants can recompose some aspects of previously learned options, do they reliably create new options or overwrite existing ones? Does the credit assignment depend on how similar the new option is to an old one? In our experiment, two groups of participants (n=124 and n=104) learned hierarchically structured options, experienced different amounts of negative transfer in a new option context, and were subsequently tested on the previously learned options. Behavioral analysis showed that old options were successfully reused without interference, and new options were appropriately created and credited. This credit assignment did not depend on how similar the new option was to the old option, showing great flexibility and precision in human hierarchical learning. These behavioral results were captured by the Option Model, providing further evidence for option learning and transfer in humans.

Reducing the Volume of Low-Value Outpatient MRI Joint Examinations in Patients ≥55 Years of Age.

PURPOSE: Magnetic resonance imaging (MRI) is not beneficial in patients with joint pain and concomitant osteoarthritis (OA). We attempt to determine whether evaluation of OA via X-rays can reduce inappropriate MRI and computed tomography (CT) arthrogram use. In our jurisdiction, CT arthrograms are used as surrogate tests because of MRI wait times. MATERIALS AND METHODS: Our intervention required patients ≥55 years of age scheduled for outpatient MRI of the knee/hip/shoulder at an urban hospital to have X-rays (weight bearing when appropriate) from within 1 year. Red flags (ie, neoplasm, infection) were identified for which MRI would be indicated regardless. Through review of radiographs on picture archiving and communication system/digital media and use of the validated Kellgren-Lawrence (KL) OA scale, radiologists assessed the presence and degree of OA. A finding of significant OA (KL > 2) without red flags would preclude MRI. Monthly averages of MRI and CT arthrogram examinations were measured 33 months before and 23 months following introduction of the intervention. RESULTS: The proportion of protocoled MRI requisitions that were avoided was 21%. If extrapolated to the province of British Columbia, 2419 of 11 700 examinations could have been prevented in the past year. The average monthly number of knee/hip/shoulder MRI examinations as a percentage of total MRI examinations decreased from 4.9% to 4.3% (P < .02) following the intervention. The average monthly number of knee/hip/shoulder CT arthrogram examinations decreased from 20.6 to 12.1 (P < .0001). CONCLUSION: We were able to decrease the number of MRI and CT arthrogram examinations in patients ≥55 years of age with joint pain by implementing an evaluation for OA via recent X-ray imaging.