When humans and other animals make decisions in their natural environments prospective rewards have to be weighed against costs. It is well established that increasing costs lead to devaluation or discounting of reward. While our knowledge about discount functions for time and probability costs is quite advanced, little is known about how physical effort discounts reward. In the present study we compared three different models in a binary choice task in which human participants had to squeeze a handgrip to earn monetary rewards: a linear, a hyperbolic, and a parabolic model. On the group as well as the individual level, the concave parabolic model explained most variance of the choice data, thus contrasting with the typical hyperbolic discounting of reward value by delay. Research on effort discounting is not only important to basic science but also holds the potential to quantify aberrant motivational states in neuropsychiatric disorders.
Perception is an active inferential process in which prior knowledge is combined with sensory input, the result of which determines the contents of awareness. Accordingly, previous experience is known to help the brain "decide" what to perceive. However, a critical aspect that has not been addressed is that previous experience can exert 2 opposing effects on perception: An attractive effect, sensitizing the brain to perceive the same again (hysteresis), or a repulsive effect, making it more likely to perceive something else (adaptation). We used functional magnetic resonance imaging and modeling to elucidate how the brain entertains these 2 opposing processes, and what determines the direction of such experience-dependent perceptual effects. We found that although affecting our perception concurrently, hysteresis and adaptation map into distinct cortical networks: a widespread network of higher-order visual and fronto-parietal areas was involved in perceptual stabilization, while adaptation was confined to early visual areas. This areal and hierarchical segregation may explain how the brain maintains the balance between exploiting redundancies and staying sensitive to new information. We provide a Bayesian model that accounts for the coexistence of hysteresis and adaptation by separating their causes into 2 distinct terms: Hysteresis alters the prior, whereas adaptation changes the sensory evidence (the likelihood function).
Voluntary selective attention can prioritize different features in a visual scene. The frontal eye-fields (FEF) are one potential source of such feature-specific top-down signals, but causal evidence for influences on visual cortex (as was shown for "spatial" attention) has remained elusive. Here, we show that transcranial magnetic stimulation (TMS) applied to right FEF increased the blood oxygen level-dependent (BOLD) signals in visual areas processing "target feature" but not in "distracter feature"-processing regions. TMS-induced BOLD signals increase in motion-responsive visual cortex (MT+) when motion was attended in a display with moving dots superimposed on face stimuli, but in face-responsive fusiform area (FFA) when faces were attended to. These TMS effects on BOLD signal in both regions were negatively related to performance (on the motion task), supporting the behavioral relevance of this pathway. Our findings provide new causal evidence for the human FEF in the control of nonspatial "feature"-based attention, mediated by dynamic influences on feature-specific visual cortex that vary with the currently attended property.
Humans tend to use the self as a reference point to perceive the world and gain information about other people's mental states. However, applying such a self-referential projection mechanism in situations where it is inappropriate can result in egocentrically biased judgments. To assess egocentricity bias in the emotional domain (EEB), we developed a novel visuo-tactile paradigm assessing the degree to which empathic judgments are biased by one's own emotions if they are incongruent to those of the person we empathize with. A first behavioral experiment confirmed the existence of such EEB, and two independent fMRI experiments revealed that overcoming biased empathic judgments is associated with increased activation in the right supramarginal gyrus (rSMG), in a location distinct from activations in right temporoparietal junction reported in previous social cognition studies. Using temporary disruption of rSMG with repetitive transcranial magnetic stimulation resulted in a substantial increase of EEB, and so did reducing visuo-tactile stimulation time as shown in an additional behavioral experiment. Our findings provide converging evidence from multiple methods and experiments that rSMG is crucial for overcoming emotional egocentricity. Effective connectivity analyses suggest that this may be achieved by early perceptual regulation processes disambiguating proprioceptive first-person information (touch) from exteroceptive third-person information (vision) during incongruency between self- and other-related affective states. Our study extends previous models of social cognition. It shows that although shared neural networks may underlie emotional understanding in some situations, an additional mechanism subserved by rSMG is needed to avoid biased social judgments in other situations.
Recent human imaging and animal studies highlight the importance of frontoamygdala circuitry in the regulation of emotional behavior and its disruption in anxiety-related disorders. Although tracing studies have suggested changes in amygdala-cortical connectivity through the adolescent period in rodents, less is known about the reciprocal connections within this circuitry across human development, when these circuits are being fine-tuned and substantial changes in emotional control are observed. The present study examined developmental changes in amygdala-prefrontal circuitry across the ages of 4-22 years using task-based functional magnetic resonance imaging. Results suggest positive amygdala-prefrontal connectivity in early childhood that switches to negative functional connectivity during the transition to adolescence. Amygdala-medial prefrontal cortex functional connectivity was significantly positive (greater than zero) among participants younger than 10 years, whereas functional connectivity was significantly negative (less than zero) among participants 10 years and older, over and above the effect of amygdala reactivity. The developmental switch in functional connectivity was paralleled by a steady decline in amygdala reactivity. Moreover, the valence switch might explain age-related improvement in task performance and a developmentally normative decline in anxiety. Initial positive connectivity followed by a valence shift to negative connectivity provides a neurobiological basis for regulatory development and may present novel insight into a more general process of developing regulatory connections.
Sättigung bedeutet, dass der Grenznutzen des Einkommens abnimmt und die Arbeitsmotivation sinkt. Die beobachtbare Konsequenz von Sättigung müsste also eine Verkürzung der Arbeitszeit bei den vergleichsweise Reicheren sein. Die vorliegende Arbeit zeigt, dass diese Schlussfolgerung falsch ist. Im Gegenteil und scheinbar paradox gilt: Sättigung wird sich eher in Form von höheren Einkommensforderungen, also gewissermassen als Gier äussern. Umgekehrt kann es jenen, die mit der Zufriedenstellung ihrer Mindestansprüche kämpfen, passieren, dass sie bei niedrigeren Lohnsätzen enden, wenn sie ihre Ansprüche reduzieren, um weniger arbeiten zu müssen.
We provide a direct test of the impact of altruism on remittances. From a sample of 105 male migrant workers from Kerala, India working in Qatar, we elicit the propensity to share with others from their responses in a dictator game, and use it as a proxy for altruism. When the entire sample is considered, we find that only migrants' income robustly explains remittances. Altruism does not seem to matter. However, we document a strong positive relationship between altruism and remittances for those migrants that report a loan obligation back home, which is nearly half the sample. We explain the role of loan obligations with a standard remittance model, extended with reference-dependent preferences.
It is proved that for public goods with zero income effects (also called Ziff public goods) tax evasion does not affect the optimal level of public expenditure. Further examples show that, in general, tax evasion may lead to less but also to more public expenditure.
This paper proposes to offer the taxpayer a choice of tax-enforcement schemes for self-selection. More specifically, the taxpayer should have the possibility of opting for the prevailing regime with a certain penalty on the evaded tax or for an alternative regime with a higher penalty on the evaded tax but a reduced tax rate. It is shown that this leads to a separation of taxpayers characterized by a relatively high degree of evasion (H-evaders) from taxpayers who evade only a relatively small amount of tax (L-evaders). Furthermore, the procedure is not self-defeating, it is effectively possible to direct the efforts of auditing towards the H-evaders. At the end of the game the L-evaders experience a welfare gain, the H-evaders are induced to reduce their evasion activities and the government can expect higher yields.
