The Search for Invariance: Repeated Positive Testing Serves the Goals of Causal Learning

Positive testing is characteristic of exploratory behavior, yet it seems to be at odds with the aim of information seeking. After all, repeated demonstrations of one’s current hypothesis often produce the same evidence and fail to distinguish it from potential alternatives. Research on the development of scientific reasoning and adult rule learning have both documented and attempted to explain this behavior. The current chapter reviews this prior work and introduces a novel theoretical account—the Search for Invariance (SI) hypothesis—which suggests that producing multiple positive examples serves the goals of causal learning. This hypothesis draws on the interventionist framework of causal reasoning, which suggests that causal learners are concerned with the invariance of candidate hypotheses. In a probabilistic and interdependent causal world, our primary goal is to determine whether, and in what contexts, our causal hypotheses provide accurate foundations for inference and intervention—not to disconfirm their alternatives. By recognizing the central role of invariance in causal learning, the phenomenon of positive testing may be reinterpreted as a rational information-seeking strategy

The effects of 10,000 voluntary contractions over 8 weeks on the strength of very weak muscles in people with spinal cord injury: a randomised controlled trial

Study design: A multi-centred, single-blinded randomised controlled trial. Objectives: To determine the effect of 10,000 voluntary contractions over 8 weeks on the strength of very weak muscles in people with spinal cord injury (SCI). Settings: Seven hospitals in Australia and Asia. Methods: One hundred and twenty people with recent SCI undergoing inpatient rehabilitation were randomised to either a Treatment or Control Group. One major muscle group from an upper or lower limb was selected if the muscle had grade 1 or grade 2 strength on a standard six-point manual muscle test. Participants allocated to the Treatment Group performed 10,000 isolated contractions of the selected muscle group, as well as usual care in 48 sessions over 8 weeks. Participants allocated to the Control Group received usual care alone. Participants were assessed at baseline and 8 weeks by a blinded assessor. The primary outcome was voluntary muscle strength on a 13-point manual muscle test. There were three secondary outcomes capturing therapists’ and participants’ perceptions of strength and function. Results: The mean between-group difference of voluntary strength at 8 weeks was 0.4/13 points (95% confidence interval −0.5 to 1.4) in favour of the Treatment Group. There were no notable between-group differences on any secondary outcome. Conclusion: Ten thousand isolated contractions of very weak muscles in people with SCI over 8 weeks has either no or a very small effect on voluntary strength

The lentinoid fungi (Lentinus and Panus) from Western Ghats, India

Panus natarajanus sp. nov. from the Western Ghats of Karnataka, India, is described, illustrated and discussed along with P. velutinus, P. tephroleucus, P. ciliatus, P. hookerianus, Lentinus fasciatus, L. concentricus, and L. megacystidiatus. Lentinus alpacus is re-allocated to Panus as P. alpacus comb. nov., and contrasted with P. parvus. A short description with illustrations is provided of L. concinnus, which is also newly reported from the Western Ghats. A synoptic key for all species of lentinoid fungi of the Western Ghats is provided