Reward context determines risky choice in pigeons and humans

Whereas humans are risk averse for monetary gains, other animals can be risk seeking for food rewards, especially when faced with variable delays or under significant deprivation. A key difference between these findings is that humans are often explicitly told about the risky options, whereas non-human animals must learn about them from their own experience. We tested pigeons (Columba livia) and humans in formally identical choice tasks where all outcomes were learned from experience. Both species were more risk seeking for larger rewards than for smaller ones. The data suggest that the largest and smallest rewards experienced are overweighted in risky choice. This observed bias towards extreme outcomes represents a key step towards a consilience of these two disparate literatures, identifying common features that drive risky choice across phyla

Comparative inspiration : from puzzles with pigeons to novel discoveries with humans in risky choice

Both humans and non-human animals regularly encounter decisions involving risk and uncertainty. This paper provides an overview of our research program examining risky decisions in which the odds and outcomes are learned through experience in people and pigeons. We summarize the results of 15 experiments across 8 publications, with a total of over 1300 participants. We highlight 4 key findings from this research: (1) people choose differently when the odds and outcomes are learned through experience compared to when they are described; (2) when making decisions from experience, people overweight values at or near the ends of the distribution of experienced values (i.e., the best and the worst, termed the “extreme-outcome rule”), which leads to more risk seeking for relative gains than for relative losses; (3) people show biases in self-reported memory whereby they are more likely to report an extreme outcome than an equally-often experienced non-extreme outcome, and they judge these extreme outcomes as having occurred more often; and (4) under certain circumstances pigeons show similar patterns of risky choice as humans, but the underlying processes may not be identical. This line of research has stimulated other research in the field of judgement and decision making, illustrating how investigations from a comparative perspective can lead in surprising directions

Assessment and Control of Spacecraft Charging Risks on the International Space Station

Electrical interactions between the F2 region ionospheric plasma and the 160V photovoltaic (PV) electrical power system on the International Space Station (ISS) can produce floating potentials (FP) on the ISS conducting structure of greater magnitude than are usually observed on spacecraft in low-Earth orbit. Flight through the geomagnetic field also causes magnetic induction charging of ISS conducting structure. Charging processes resulting from interaction of ISS with auroral electrons may also contribute to charging albeit rarely. The magnitude and frequency of occurrence of possibly hazardous charging events depends on the ISS assembly stage (six more 160V PV arrays will be added to ISS), ISS flight configuration, ISS position (latitude and longitude), and the natural variability in the ionospheric flight environment. At present, ISS is equipped with two plasma contactors designed to control ISS FP to within 40 volts of the ambient F2 plasma. The negative-polarity grounding scheme utilized in the ISS 160V power system leads, naturally, to negative values of ISS FP. A negative ISS structural FP leads to application of electrostatic fields across the dielectrics that separate conducting structure from the ambient F2 plasma, thereby enabling dielectric breakdown and arcing. Degradation of some thermal control coatings and noise in electrical systems can result. Continued review and evaluation of the putative charging hazards, as required by the ISS Program Office, revealed that ISS charging could produce a risk of electric shock to the ISS crew during extra vehicular activity. ISS charging risks are being evaluated in ongoing ISS charging measurements and analysis campaigns. The results of ISS charging measurements are combined with a recently developed detailed model of the ISS charging process and an extensive analysis of historical ionospheric variability data, to assess ISS charging risks using Probabilistic Risk Assessment (PRA) methods. The PRA analysis (estimated frequency of occurrence and severity of the charging hazards) are then used to select the hazard control strategy that provides the best overall safety and mission success environment for ISS and the ISS crew. This paper presents: 1) a summary of ISS spacecraft charging analysis, measurements, observations made to date, 2) plans for future ISS spacecraft charging measurement campaigns, and 3) a detailed discussion of the PRA strategy used to assess ISS spacecraft charging risks and select charging hazard control strategie

Searching by Rules: Pigeons’ (\u3ci\u3eColumba livia\u3c/i\u3e) Landmark-Based Search According to Constant Bearing or Constant Distance

Pigeons (Columba livia) searched for a goal location defined by a constant relative spatial relationship to 2 landmarks. For one group, landmark-to-goal bearings remained constant while distance varied. For another group, landmark-to-goal distances remained constant while direction varied. Birds were trained with 4 interlandmark distances and then tested with 5 novel interlandmark distances. Overall error magnitude was similar across groups and was larger than previously reported for Clark’s nutcrackers (Nucifraga columbiana). During training, error magnitude increased with interlandmark distance for constant-bearing but not constant-distance birds. Both groups searched less accurately along the axis parallel to landmarks than along the perpendicular axis. Error magnitude increased with novel extrapolated interlandmark distances but not with novel interpolated distances. Results suggest modest geometric rule learning by pigeons

The power of nothing : risk preference in pigeons, but not people, is driven primarily by avoidance of zero outcomes

When making risky decisions, people and pigeons often show similar choice patterns. When people learn the reward probabilities through repeated exposure to the outcomes, their preference is disproportionately influenced by the extreme (highest and lowest) outcomes occurring in the decision context. Overweighting of these extremes increases preference for risky alternatives that lead to the highest outcome and decreases preference for risky alternatives that lead to the lowest outcome, termed the extreme-outcome rule. This rule predicts greater risk seeking for choices between safe and risky high-value outcomes than for choices between safe and risky low-value outcomes, when both choices occur in the same context. In a series of studies, we examine how this extreme-outcome rule generalizes within and across two evolutionary distant species: pigeons (Columba livia) and humans (Homo sapiens). Both species showed risky choices consistent with the extreme-outcome rule when a low-value risky option could yield an outcome of zero. When all outcome values were increased such that none of the options could lead to zero, people but not pigeons were still consistent with the extreme-outcome rule. Unlike people, pigeons no longer avoided a low-value risky option when it yielded a non-zero food outcome. These results suggest that, despite some similarities, different mechanisms underlie risky choice in pigeons and people

Temporal summation of global form signals in dynamic Glass patterns

AbstractThe ability to perceive complex objects in the environment requires that the visual system integrate local form information into global shapes. Glass patterns (GPs) are stimuli that are commonly used to study this integration process. GPs consist of randomly positioned dot-pairs oriented in a coherent way to create a global form. When multiple GPs are presented sequentially, observers report a percept of illusory coherent motion and have lower detection thresholds relative to a single presentation GPs. The percept of illusory motion has been attributed to the visual system interpreting the dot-pairs in GPs as motion streaks. However, it remains unclear why dynamic GPs are detected at lower thresholds than static GPs. Two main differences exist between static and dynamic GPs: (a) dynamic GPs contain multiple presentations of global form signals compared to a single presentation in static GPs and (b) dynamic GPs have a greater temporal frequency than static GPs. Here we investigated which of these two factors contributed to the heightened sensitivities for dynamic GPs. We systematically varied the number of unique GPs and the rate at which each unique frame is presented (i.e., temporal frequency). The results show that, within the range of temporal frequency used, the primary influence on detection thresholds was the number of unique frames. These results suggest that the improved detection sensitivities can be driven by a mechanism of temporal summation of global form

When good news leads to bad choices

Pigeons and other animals sometimes deviate from optimal choice behavior when given informative signals for delayed outcomes. For example, when pigeons are given a choice between an alternative that always leads to food after a delay and an alternative that leads to food only half of the time after a delay, preference changes dramatically depending on whether the stimuli during the delays are correlated with (signal) the outcomes or not. With signaled outcomes, pigeons show a much greater preference for the suboptimal alternative than with unsignaled outcomes. Key variables and research findings related to this phenomenon are reviewed, including the effects of durations of the choice and delay periods, probability of reinforcement, and gaps in the signal. We interpret the available evidence as reflecting a preference induced by signals for good news in a context of uncertainty. Other explanations are briefly summarized and compared

Perception of dynamic Glass patterns

AbstractIn the mammalian brain, form and motion are processed through two distinct pathways at early stages of visual processing. However, recent evidence suggests that these two pathways may interact. Here we used dynamic Glass patterns, which have been previously shown to create the perception of coherent motion in humans, despite containing no motion coherence. Glass patterns are static stimuli that consist of randomly positioned dot pairs that are integrated spatially to create the perception of a global form, whereas dynamic Glass patterns consist of several independently generated static Glass patterns presented sequentially. In the current study, we measured the detection threshold of five types of dynamic Glass patterns and compared the rank order of the detection thresholds with those found for static Glass patterns and real motion patterns (using random dot stimuli). With both the static Glass patterns and dynamic Glass patterns, detection thresholds were lowest for concentric and radial patterns and highest for horizontal patterns. We also found that vertical patterns were better detected than horizontal patterns, consistent with prior evidence of a “horizontal effect” in the perception of natural scene images. With real motion, detection thresholds were equivalent across all patterns, with the exception of higher thresholds for spiral patterns. Our results suggest that dynamic Glass patterns are processed primarily as form prior to input into the motion system