Study of Intertemporal Discounting According to Age Groups

The paper focuses on the topic of intertemporal discounting of individuals according to age groups. Using the sample of examined individuals, it aims to verify the hypothesis that the patience of individuals decreases with their increasing age. The study included a total of 599 individuals with an average age of 38.3 years (min. 16 and max. 82 years) who answered classical questions focused on time discounting and impulsive behaviour. In total, four possible scenarios were analysed: a small reward (CZK 100) with a delay of 1 day, a small reward with a delay of 1 month, a large reward (CZK 100,000) with a delay of 1 day and a large reward with a delay of 1 month. The delayed reward was always increased by 10% (i.e., CZK 110 or CZK 110,000). The basic hypothesis was that with increasing age, the subjective discount rate increases i.e., patience decreases. The above-mentioned 4 scenarios were evaluated for the hypotheses, while only three of the four scenarios were confirmed for all hypotheses. The results in the examined individuals suggest that with increasing age, there is a decrease in patience and at the same time a decrease in impulsive behaviour. These findings may have an overlap in consumption or savings in relation to the aging population.

The effect of age on discrimination learning and self-control in a marshmallow test for pigs

Both humans and nonhuman animals need to show self-control and wait for a larger or better reward instead of a smaller or less preferred but instant reward on an everyday basis. We investigated whether this ability undergoes ontogenetic development in domestic pigs (similar to what is known in human infants) by testing if and for how long nine- and 16-week-old pigs wait for a larger amount of their preferred reward. In a delay-of-gratification task, animals first learned that a small reward was hidden under a white cup and a large reward under a black cup, and then the delay to deliver the large reward was gradually increased. The results show that older pigs could wait longer for a larger reward than younger pigs (10.6 ± 1.3 s vs. 5.2 ± 1.5 s), thereby confirming our hypothesis of ontogenetic development of self-control in pigs. This self-control is likely to be regulated by the behavioural inhibition system and associated systems. Self-control or, more specifically the lack of it may be involved in the development of abnormal behaviours, not only in humans but also in animals. Therefore, research on self-control in decision-making might provide a new perspective on abnormal behaviours in captive animals.

Sequential delay and probability discounting tasks in mice reveal anchoring effects partially attributable to decision noise

Delay discounting and probability discounting decision making tasks in rodent models have high translational potential. However, it is unclear whether the discounted value of the large reward option is the main contributor to variability in animals' choices in either task, which may limit translatability to human discounting data. Male and female mice underwent sessions of delay and probability discounting in sequence to assess how choice behavior adapts over experience with each task. To control for "anchoring" (persistent choices based on the initial delay or probability), mice experienced "Worsening" schedules where the large reward was offered under initially favorable delay or probability conditions that became less favorable during testing, followed by "Improving" schedules where the large reward was offered under initially unfavorable conditions that improved over a session. During delay discounting, both male and female mice showed elimination of anchoring effects over training. In probability discounting, both sexes of mice continued to show some anchoring even after months of training. One possibility is that noisy action selection could contribute to these anchoring effects, rather than persistent fluctuations in value discounting. We fit choice behavior in individual animals using models that included both a value-based discounting parameter and a decision noise parameter that captured variability in choices deviating from value maximization. Changes in anchoring behavior over time were tracked by changes in our decision noise parameter, not the value parameter. Thus, changes in discounting behavior in mice can result from changes in exploration of the environment rather than changes in reward valuation.

Flying the Flag

With MacArthur’s return to the Philippines grabbing the headlines, the navy made renewed efforts to publicize its battles in the central Pacific. Photojournalists were the biggest beneficiaries, with access to a new laboratory on Guam and fewer censorship rules. During the bloody battle on Iwo Jima, these improvements reaped a large reward, with the prompt publication of Joe Rosenthal’s famous picture of the flag raising on the top of Mount Suribachi. During the next campaign, on Okinawa, the correspondents struggled to achieve the same impact. Ernie Pyle, the most prominent of them, fell to an enemy bullet, while the survivors initially had to compete for front-page space with the end of the war in Europe.

Parametric shift from rational to irrational decisions in mice

In the classical view of economic choices, subjects make rational decisions evaluating the costs and benefits of options in order to maximize their overall income. Nonetheless, subjects often fail to reach optimal outcomes. The overt value of an option drives the direction of decisions, but covert factors such as emotion and sensitivity to sunk cost are thought to drive the observed deviations from optimality. Many questions remain to be answered as to (1) which contexts contribute the most to deviation from an optimal solution; and (2) the extent of these effects. In order to tackle these questions, we devised a decision-making task for mice, in which cost and benefit parameters could be independently and flexibly adjusted and for which a tractable optimal solution was known. Comparing mouse behavior with this optimal solution across parameter settings revealed that the factor most strongly contributing to suboptimal performance was the cost parameter. The quantification of sensitivity to sunk cost, a covert factor implicated in our task design, revealed it as another contributor to reduced optimality. In one condition where the large reward option was particularly unattractive and the small reward cost was low, the sensitivity to sunk cost and the cost-led suboptimality almost vanished. In this regime and this regime only, mice could be viewed as close to rational (here, ‘rational’ refers to a state in which an animal makes decisions basing on objective valuation, not covert factors). Taken together, our results suggest that “rationality” is a task-specific construct even in mice.

Single-trial dynamics of hippocampal spatial representations are modulated by reward value

Reward value is known to modulate learning speed in spatial memory tasks, but little is known about its influence on the dynamical changes in hippocampal spatial representations. Here, we monitored the trial-to-trial changes in hippocampal place cell activity during the acquisition of place-reward associations with varying reward size. We show a faster reorganization and stabilization of the hippocampal place map when a goal location is associated with a large reward. The reorganization is driven by both rate changes and the appearance and disappearance of place fields. The occurrence of hippocampal replay activity largely followed the dynamics of changes in spatial representations. Replay patterns became more selectively tuned towards behaviorally relevant experiences over the course of learning. These results suggests that high reward value enhances memory retention via accelerating the formation and stabilization of the hippocampal cognitive map and enhancing its reactivation during learning.

Preschoolers in Belarus and Turkey accept an adult’s counterintuitive claim and do not spontaneously seek evidence to test that claim

When presented with a claim that contradicts their intuitions, do children seize opportunities to empirically verify such claims or do they simply acquiesce to what they have been told? To answer this question, we conducted a replication of Ronfard et al. (conducted in the People’s Republic of China) in two countries with distinct religious and political histories (Study 1: Belarus, N = 74; Study 2: Turkey, N = 79). Preschool children were presented with five different-sized Russian dolls and asked to indicate the heaviest doll. All children selected the biggest doll. Half of the children then heard a (false) claim (i.e., that the smallest doll was the heaviest), contradicting their initial intuition. The remaining children heard a (true) claim (i.e., that the biggest doll was the heaviest), confirming their initial intuition. Belarusian and Turkish preschoolers typically endorsed the experimenter’s claim no matter whether it had contradicted or confirmed their initial intuition. Next, the experimenter left the room, giving children an opportunity to check the experimenter’s claim by picking up the relevant dolls. Belarusian and Turkish preschoolers rarely explored the dolls, regardless of the type of testimony they received and continued to endorse the counterintuitive testimony they received. Furthermore, in Study 2, Turkish preschoolers continued to endorse smallest = heaviest even when doing so could have cost them a large reward. In sum, across two different cultural contexts, preschool children endorsed a counterintuitive claim and did not spontaneously seek evidence to test it. These results confirm and extend those of Ronfard et al.

Effects of early life and current housing on sensitivity to reward loss in a successive negative contrast test in pigs

Animals in a negative affective state seem to be more sensitive to reward loss, i.e. an unexpected decrease in reward size. The aim of this study was to investigate whether early-life and current enriched vs. barren housing conditions affect the sensitivity to reward loss in pigs using a successive negative contrast test. Pigs (n = 64 from 32 pens) were housed in barren or enriched conditions from birth onwards, and at 7 weeks of age experienced either a switch in housing conditions (from barren to enriched or vice versa) or not. Allotting pigs to the different treatments was balanced for coping style (proactive vs. reactive). One pig per pen was trained to run for a large reward and one for a small reward. Reward loss was introduced for pigs receiving the large reward after 11 days (reward downshift), i.e. from then onwards, they received the small reward. Pigs housed in barren conditions throughout life generally had a lower probability and higher latency to get the reward than other pigs. Proactive pigs ran overall slower than reactive pigs. After the reward downshift, all pigs ran slower. Nevertheless, reward downshift increased the latency and reduced the probability to get to the reward, but only in pigs exposed to barren conditions in early life, which thus were more sensitive to reward loss than pigs from enriched early life housing. In conclusion, barren housed pigs seemed overall less motivated for the reward, and early life housing conditions had long-term effects on the sensitivity to reward loss.

Cerebellar climbing fibers encode expected reward size

Climbing fiber inputs to the cerebellum encode error signals that instruct learning. Recently, evidence has accumulated to suggest that the cerebellum is also involved in the processing of reward. To study how rewarding events are encoded, we recorded the activity of climbing fibers when monkeys were engaged in an eye movement task. At the beginning of each trial, the monkeys were cued to the size of the reward that would be delivered upon successful completion of the trial. Climbing fiber activity increased when the monkeys were presented with a cue indicating a large reward, but not a small reward. Reward size did not modulate activity at reward delivery or during eye movements. Comparison between climbing fiber and simple spike activity indicated different interactions for coding of movement and reward. These results indicate that climbing fibers encode the expected reward size and suggest a general role of the cerebellum in associative learning beyond error correction.

Overt attentional capture by reward-related stimuli overcomes inhibitory suppression

Salient-but-irrelevant distractors can automatically capture attention and eye-gaze in visualsearch. However, recent findings have suggested that attention to salient-but-irrelevant stimulican be suppressed when observers use a specific target template to guide their search (i.e.,feature search). A separate line of research has indicated that attentional selection isinfluenced by factors other than the physical salience of a stimulus and the observer’s goals.For instance, pairing a stimulus with reward has been shown to increase the extent to which itcaptures attention and gaze (as though it has become more physically salient), even when suchcapture has negative consequences for the observer. Here we used eye-tracking with arewarded visual search task to investigate whether capture by reward can be suppressed in thesame way as capture by physical salience. When participants were encouraged to use featuresearch, attention to a distractor paired with relatively small reward was suppressed. However,under the same conditions attention was captured by a distractor paired with large reward,even when such capture resulted in reward omission. These findings suggest thatreward-related stimuli are given special priority within the visual attention system over andabove physically-salient stimuli, and have implications for our understanding of real-worldbiases to reward-related stimuli, such as those seen in addiction.