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Providing patients with timely care from the appropriate unit involves both correct clinical evaluation of patient needs and making admission decisions to effectively manage a unit with limited capacity in the face of stochastic patient arrivals and lengths of stay. We study human decision behavior in the latter operations management task. Using behavioral models and controlled experiments in which physicians and MTurk workers manage a simulated hospital unit, we identify cognitive and environmental factors that drive systematic admission decision bias. We report on two main findings. First, seemingly innocuous “occupancy information hurdles” (e.g., having to type a password to view current occupancy) can cause a chain of events that leads physicians to maintain systematically lower unit utilization. Specifically, these hurdles cause physicians to make most admission decisions without checking the current unit occupancy. Then—between the times that they do check—physicians underestimate the number of available beds when occupancy increases from admissions are more salient than occupancy decreases from discharges. Second, decision-related random error or “noise” leads to higher- or lower-than-optimal utilization of hospital units in predictable patterns, depending on the system parameters. We provide evidence that these patterns are due to some settings providing more opportunity for physicians to mistakenly admit patients and other settings that provide more opportunity to mistakenly reject patients. These findings help identify when and why clinicians are likely to make inefficient decisions because of human cognitive limitations and suggest mitigation strategies to help hospital units improve their capacity management. This paper was accepted by Charles Corbett, operations management.

In humans, the short allele of a common polymorphism in the serotonin transporter (5-HTT) gene is associated with a higher risk to develop depression and anxiety disorders. Furthermore, individuals carrying this allele are characterized by negative judgment biases, as they tend to interpret ambiguous information in a more pessimistic way. 5-HTT knockout mice, lacking the 5-HTT gene either homo- or heterozygously, provide a widely used model organism for the study of symptoms related to human anxiety disorders. In the present study, we aimed to prove the anxiety-like phenotype of the 5-HTT mouse model, and to investigate whether 5-HTT genotype also causes differences in judgment bias. While our results confirm that homozygous 5-HTT knockout mice display highest levels of anxiety-like behavior, it was decreased in heterozygous mice. Against our expectations, we did not detect differences in the animals' judgment bias. These results indicate that at least in mice the association between 5-HTT genotype and judgment bias is not straightforward and that other factors, including multiple genes as well as environmental influences, are implicated in the modulation of judgment biases. More research is needed to gain further insights into their function as potential endophenotypes for psychopathology.

Exploration tendency, one of the most investigated animal personality traits, may be driven by either positive (when seeking interesting information) or negative (to reduce the uncertainty of the environment) affective/emotional profiles. To disentangle the valence of the affective state associated with exploration trait, we applied a judgment bias test to evaluate the animals’ responses in an ambiguous situation, allowing an assessment of their affective state or mood. Experiments were carried out in male house mice (Mus musculus) of wild origin. Individual differences in exploration tendency were assessed by repeated open field and novel object tests. To evaluate the animals’ judgment bias, we trained the subjects for 8 days in a 3-arm maze to discriminate between two extreme locations (outer arms: either positively reinforced with sugary water or less-positively reinforced with plain water), in terms of a shorter latency to approach the positively reinforced arm. After this learning criterion was reached, we repeatedly tested their responses to an ambiguous location (intermediate arm). The latencies to approach and consume the ambiguous reward were highly repeatable over the 3 days of testing; hence individuals expressed a stable judgment bias. Most importantly, more exploratory animals showed a more negative judgment bias, which supports the hypothesis that a higher exploration tendency was associated with a negative affective state. Further studies should investigate whether exploration in different situations might be due to distinct affective states.

Natural selection can act on between-individual variation in cognitive abilities, yet evolutionary responses depend on the presence of underlying genetic variation. It is, therefore, crucial to determine the relative extent of genetic versus environmental control of these among-individual differences in cognitive traits to understand their causes and evolutionary potential. We investigated heritability of associative learning performance and of a cognitive judgement bias (optimism), as well as their covariation, in a captive pedigree-bred population of red junglefowl (Gallus gallus, n > 300 chicks over 5 years). We analysed performance in discriminative and reversal learning (two facets of associative learning), and cognitive judgement bias, by conducting animal models to disentangle genetic from environmental contributions. We demonstrate moderate heritability for reversal learning, and weak to no heritability for optimism and discriminative learning, respectively. The two facets of associative learning were weakly negatively correlated, consistent with hypothesized trade-offs underpinning individual cognitive styles. Reversal, but not discriminative learning performance, was associated with judgement bias; less optimistic individuals reversed a previously learnt association faster. Together these results indicate that genetic and environmental contributions differ among traits. While modular models of cognitive abilities predict a lack of common genetic control for different cognitive traits, further investigation is required to fully ascertain the degree of covariation between a broader range of cognitive traits and the extent of any shared genetic control. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.

Several cognitive theories of depression have proposed that cognitive judgment bias determines individual vulnerability to this disorder. Indeed, we have recently demonstrated a relationship between pessimistic judgment bias and vulnerability of rats to the stress-induced anhedonia, and a negative correlation between the level of pessimism and motivation. To further characterize the effects of trait pessimism on cognitive processes associated with depression, in the present study we compared the sensitivity of rats displaying optimistic and pessimistic traits to positive and negative feedback. The animals were initially trained and tested in the rat version of the probabilistic reversal-learning (PRL) task, which allowed for the assessment of feedback sensitivity in individual animals. Subsequently, the rats were re-trained and tested in a series of ambiguous-cue interpretation (ACI) tests, which allowed for the classification of animals displaying “optimistic” and “pessimistic” traits. The “pessimistic” rats were significantly more sensitive to negative feedback than their “optimistic” conspecifics, as indicated by an increased proportion of lose-shift behaviors. The results of our study demonstrate the interrelation and co-existence of two cognitive biases that may predict vulnerability to depressive disorder.

In humans, optimism is a cognitive construct related to motivation; optimists exert effort, whereas pessimists disengage from effort. In this study, using a recently developed ambiguous-cue interpretation (ACI) paradigm we took the unique opportunity to investigate whether \"optimism\" as a trait is correlated with motivation in rodents. In a series of ACI tests (cognitive bias screening, CBS), we identified rats displaying \"pessimistic\" and \"optimistic\" traits. Subsequently, we investigated the trait differences in the motivation of these rats to gain reward and to avoid punishment using a progressive ratio (PR) schedule of reinforcement paradigm. Although \"optimistic\" and \"pessimistic\" animals did not differ in their motivation to avoid punishment, the \"optimistic\" rats were significantly more motivated to gain reward than their \"pessimistic\" conspecifics. For the first time, we showed an association between cognitive judgment bias and motivation in an animal model. Because both investigated processes are closely related to mental health and wellbeing, our results may be valuable for preclinical modeling of many psychiatric disorders.

The provision of environmental enrichment is a frequently used refinement method to improve welfare of laboratory animals. Compared to barren housing conditions, enrichment could decrease signs of impaired welfare, such as stress hormone concentrations and stereotypies. Moreover, the provision of enrichment was found to positively affect animals’ emotional states, reflected by more optimistic judgements in cognitive bias paradigms. To investigate the impact of environmental enrichment beyond the classical comparison between barren and enriched housing, the aim of this study was to examine the influence of two different enrichment regimes on the cognitive judgement bias of laboratory rats ( Rattus norvegicus f. domestica) . Twenty-one individuals were housed either under consistent enrichment or regular enrichment change for several months. Afterwards, they participated in a cognitive judgement bias test, which is based on ambiguous cue interpretations and enables a classification of rats as being optimistic or pessimistic. Interestingly, we found that rats from the enrichment-change group responded more optimistically in an ambiguous situation than rats from the consistent-enrichment group. It seems that the regular enrichment change could induce a more positive emotional state in our rats and, therefore, represents a simple but effective approach to improve welfare under laboratory conditions.

Rationale and objectives Both valproic acid (VPA) and lithium (LI) are well-established treatments for therapy of intense and sustained mood shifts, which are characteristics of affective disorders, such as bipolar disorder (BP). As mood and cognitive judgment bias have been found to be strongly interrelated, the present study investigated, in an animal model, whether acute treatment with VPA or LI could affect cognitive judgment bias. Methods To accomplish this goal, two groups of rats received single injections of either VPA or LI after initial behavioral training and were subsequently tested with the ambiguous-cue interpretation (ACI) test. Both drugs were administered in three doses using the fully randomized Latin square design. Results VPA (100, 200, and 400 mg/kg) had no significant effect on the interpretation of the ambiguous cue. LI at the lowest dose (10 mg/kg) had no effect; at an intermediate dose (50 mg/kg), it significantly biased animals towards positive interpretation of the ambiguous cue, and at the highest dose (100 mg/kg), it impaired the ability of animals to complete the test. Conclusion To our knowledge, this is the first study demonstrating lithium’s effects on increased optimistic judgment bias. Future studies may focus on the ability of putative pharmacotherapies to modify the cognitive judgment bias dimension of patients at risk for bipolar disorder or depression.

Although the cognitive theory has implicated judgment bias in various psychopathologies, its role in decision making under risk remains relatively unexplored. In the present study, we assessed the effects of cognitive judgment bias on risky choices in rats. First, we trained and tested the animals on the rat version of the probability-discounting (PD) task. During discrete trials, the rats chose between two levers; a press on the \"small/certain\" lever always resulted in the delivery of one reward pellet, whereas a press on the \"large/risky\" lever resulted in the delivery of four pellets. However, the probability of receiving a reward from the \"large/risky\" lever gradually decreased over the four trial blocks. Subsequently, the rats were re-trained and evaluated on a series of ambiguous-cue interpretation (ACI) tests, which permitted their classification according to the display of \"optimistic\" or \"pessimistic\" traits. Because dopamine (DA) has been implicated in both: risky choices and optimism, in the last experiment, we compared the reactivity of the dopaminergic system in the \"optimistic\" and \"pessimistic\" animals using the apomorphine (APO; 2 mg/kg s.c.) sensitivity test. We demonstrated that as risk increased, the proportion of risky lever choices decreased significantly slower in \"optimists\" compared with \"pessimists\" and that these differences between the two groups of rats were associated with different levels of dopaminergic system reactivity. Our findings suggest that cognitive judgment bias, risky decision-making and DA are linked, and they provide a foundation for further investigation of the behavioral traits and cognitive processes that influence risky choices in animal models.

Rationale Animal models of mania lack genuine cognitive parameters. The present gold standard of mania models, amphetamine-induced hyperlocomotion, is rather unspecific and does not necessarily target its cardinal symptoms. Therefore, alternative behavioral markers that are sensitive to stimulants are required. Objectives In the present study, by combining the psychostimulant-induced model of mania in rodents with the recently developed ambiguous-cue interpretation (ACI) tests, we investigated the effects of chronic administration of d -amphetamine and cocaine on the cognitive judgment bias of rats. Methods To accomplish this goal, in two separate experiments, previously trained animals received chronic, daily injections of either d -amphetamine (2 mg/kg) or cocaine (10 mg/kg) for 2 weeks and were subsequently tested with the ACI procedure. Results Chronic treatment with both psychostimulants did not make rats more “optimistic.” Conclusions The results are discussed in terms of behavioral and pharmacological actions of the tested compounds and their implications for modeling mania in animals.