Relationship between soil and groundwater salinity in the Western Canada Sedimentary Basin.

Saturated soil paste extracts indicate soluble ions in soil pore water that are available to vegetation. As such, they are thought to accurately describe the relationship between soil and groundwater salinity. To test this assumption, soil and groundwater samples were collected from 575 monitoring wells in saline regions of the Western Canadian Sedimentary Basin (WCSB). Samples were analyzed for electrical conductivity (EC) and Cl-, Na+, Ca2+, Mg2+, K+, SO42-, and HCO- 3 content. We compared groundwater ionic concentrations to paste extracts derived from matching soils, finding that differences from in situ soil porosity cause saturated pastes to underestimate groundwater salinity. Therefore, we provide pedotransfer functions for accurately calculating groundwater quality from soil data. In addition, we discuss the effects of porosity and soil composition on the saturated paste method, as measured through hydraulic conductivity, saturation percent, and sample lithology. Groundwater salinity may also influence further leaching of salts from soil. As produced water (NaCl brine) spills are common across the sulfate-rich soils of the WCSB, we considered the effects of NaCl on leaching of other ions, finding that influx of Na+ into groundwater is associated with increased sulfate leaching from soil. Therefore, considering the secondary effects of produced water on groundwater quality is essential to spill management.

Implicit Valuation of the Near-Miss is Dependent on Outcome Context.

Gambling studies have described a "near-miss effect" wherein the experience of almost winning increases gambling persistence. The near-miss has been proposed to inflate the value of preceding actions through its perceptual similarity to wins. We demonstrate here, however, that it acts as a conditioned stimulus to positively or negatively influence valuation, dependent on reward expectation and cognitive engagement. When subjects are asked to choose between two simulated slot machines, near-misses increase valuation of machines with a low payout rate, whereas they decrease valuation of high payout machines. This contextual effect impairs decisions and persists regardless of manipulations to outcome feedback or financial incentive provided for good performance. It is consistent with proposals that near-misses cause frustration when wins are expected, and we propose that it increases choice stochasticity and overrides avoidance of low-valued options. Intriguingly, the near-miss effect disappears when subjects are required to explicitly value machines by placing bets, rather than choosing between them. We propose that this task increases cognitive engagement and recruits participation of brain regions involved in cognitive processing, causing inhibition of otherwise dominant systems of decision-making. Our results reveal that only implicit, rather than explicit strategies of decision-making are affected by near-misses, and that the brain can fluidly shift between these strategies according to task demands.

Cannabis use is associated with sexually dimorphic changes in executive control of visuospatial decision-making.

When the outcome of a choice is less favorable than expected, humans and animals typically shift to an alternate choice option on subsequent trials. Several lines of evidence indicate that this "lose-shift" responding is an innate sensorimotor response strategy that is normally suppressed by executive function. Therefore, the lose-shift response provides a covert gauge of cognitive control over choice mechanisms. We report here that the spatial position, rather than visual features, of choice targets drives the lose-shift effect. Furthermore, the ability to inhibit lose-shift responding to gain reward is different among male and female habitual cannabis users. Increased self-reported cannabis use was concordant with suppressed response flexibility and an increased tendency to lose-shift in women, which reduced performance in a choice task in which random responding is the optimal strategy. On the other hand, increased cannabis use in men was concordant with reduced reliance on spatial cues during decision-making, and had no impact on the number of correct responses. These data (63,600 trials from 106 participants) provide strong evidence that spatial-motor processing is an important component of economic decision-making, and that its governance by executive systems is different in men and women who use cannabis frequently.

Lose-Shift Responding in Humans Is Promoted by Increased Cognitive Load.

The propensity of animals to shift choices immediately after unexpectedly poor reinforcement outcomes is a pervasive strategy across species and tasks. We report here on the memory supporting such lose-shift responding in humans, assessed using a binary choice task in which random responding is the optimal strategy. Participants exhibited little lose-shift responding when fully attending to the task, but this increased by 30%-40% in participants that performed with additional cognitive load that is known to tax executive systems. Lose-shift responding in the cognitively loaded adults persisted throughout the testing session, despite being a sub-optimal strategy, but was less likely as the time increased between reinforcement and the subsequent choice. Furthermore, children (5-9 years old) without load performed similarly to the cognitively loaded adults. This effect disappeared in older children aged 11-13 years old. These data provide evidence supporting our hypothesis that lose-shift responding is a default and reflexive strategy in the mammalian brain, likely mediated by a decaying memory trace, and is normally suppressed by executive systems. Reducing the efficacy of executive control by cognitive load (adults) or underdevelopment (children) increases its prevalence. It may therefore be an important component to consider when interpreting choice data, and may serve as an objective behavioral assay of executive function in humans that is easy to measure.