Constantinos Hadjichristidis

The probability of causal conditionals.

Conditionals in natural language are central to reasoning and decision making. A theoretical proposal called the Ramsey test implies the conditional probability hypothesis: that the subjective probability of a natural language conditional, P(if p then q), is the conditional subjective probability, P(q/p). We report three experiments on causal indicative conditionals and related counterfactuals that support this hypothesis. We measured the probabilities people assigned to truth table cases, P(pq), P(p notq), P( notpq) and P( notp notq). From these ratings, we computed three independent predictors, P(p), P(q/p) and P(q/ notp), that we then entered into a regression equation with judged P(if p then q) as the dependent variable. In line with the conditional probability hypothesis, P(q/p) was by far the strongest predictor in our experiments. This result is inconsistent with the claim that causal conditionals are the material conditionals of elementary logic. Instead, it supports the Ramsey test hypothesis, implying that common processes underlie the use of conditionals in reasoning and judgments of conditional probability in decision making.

Typical Versus Atypical Unpacking and Superadditive Probability Judgment

Probability judgments for packed descriptions of events (e.g., the probability that a businessman does business with a European country) are compared with judgments for unpacked descriptions of the same events (e.g., the probability that a businessman does business with England, France, or some other European country). The prediction that unpacking can decrease probability judgments, derived from the hypothesis that category descriptions are interpreted narrowly in terms of typical instances, is contrasted to the prediction of support theory that unpacking will generally increase judged probabilities (A. Tversky & D. J. Koehler, 1994). The authors varied the typicality of unpacked instances and found no effect of unpacking with typical instances (additivity) and a negative effect with atypical instances (superadditivity). Support theory cannot account for these findings in its current formulation.

The Foreign Language Effect on Moral Judgment: The Role of Emotions and Norms

We investigated whether and why the use of a foreign language influences moral judgment. We studied the trolley and footbridge dilemmas, which propose an action that involves killing one individual to save five. In line with prior work, the use of a foreign language increased the endorsement of such consequentialist actions for the footbridge dilemma, but not for the trolley dilemma. But contrary to recent theorizing, this effect was not driven by an attenuation of emotions. An attenuation of emotions was found in both dilemmas, and it did not mediate the foreign language effect on moral judgment. An examination of additional scenarios revealed that foreign language influenced moral judgment when the proposed action involved a social or moral norm violation. We propose that foreign language influences moral judgment by reducing access to normative knowledge.

Pecunia olet: the role of incidental disgust in the ultimatum game.

We address the role of the incidental emotion of disgust in the Ultimatum Game. Participants had to choose whether or not to accept a €2 offer from a €10 pot made by another participant; 120 were in a room where a disgusting smell was released and 120 were in a room with no particular smell. Acceptance rates were higher in the room with the disgusting smell. The effect was mainly carried by the male participants who also reported more disgust with the disgusting smell and judged the offer as less unfair than females. We propose a spontaneous discounting explanation. Acceptance rates were higher in the room with the disgusting smell because participants misattributed the disgust induced by the offer to the ambient disgusting smell.

Foreign language affects the contribution of intentions and outcomes to moral judgment.

We examine whether the use of a foreign language, as opposed to the native language, influences the relative weight intentions versus outcomes carry in moral evaluations. In Study 1, participants were presented with actions that had positive outcomes but were motivated by dubious intentions, while in Study 2 with actions that had negative outcomes but were motivated by positive intentions. Participants received the materials either in their native or a foreign language. Foreign language prompted more positive moral evaluations in Study 1 and less positive evaluations in Study 2. These results show that foreign language reduces the relative weight placed on intentions versus outcomes. We discuss several theoretical accounts that are consistent with the results such as that foreign language attenuates emotions (triggered by intentions) or it depletes cognitive resources.

Uncertain premises and Jeffrey's rule

Oaksford & Chater (O&C) begin in the halfway Bayesian house of assuming that minor premises in conditional inferences are certain. We demonstrate that this assumption is a serious limitation. They additionally suggest that appealing to Jeffreys rule could make their approach more general. We present evidence that this rule is not limited enough to account for actual probability judgements.

Iffy beliefs: Conditional thinking and belief change

The ability to entertain possibilities and draw inferences about them is essential to human intelligence. We examine the hypothesis that conditionalif-then statements trigger a mental simulation process in which people suppose the antecedent (if statement) to be true and evaluate the consequent (then statement) in that context. On the assumption that supposing an event to be true increases belief that the event has occurred or will occur, this hypothesis is consistent with the claim that evaluating a conditional will heighten belief in its antecedent more than in its consequent. Two experiments, employing conditionals of the formIf animal A has property X, then animal B will have property X, in which X was a property that people could not readily relate to the animals, supported this claim. The effect was stronger following the evaluation of conditionals with dissimilar animal categories.

To make people save energy tell them what others do but also who they are: a preliminary study

A way to make people save energy is by informing them that “comparable others” save more. We investigated whether, one can further improve this nudge by manipulating Who the “comparable others” are. We asked participants to imagine receiving feedback stating that their energy consumption exceeded that of “comparable others” by 10%. We varied Who the “comparable others” were in a 2 × 2 design: they were a household that was located either in the same neighborhood as themselves or in a different neighborhood, and its members were either identified (by names and a photograph) or unidentified. We also included two control conditions: one where no feedback was provided, and one where only statistical feedback was provided (feedback about an average household). We found that it matters Who the “comparable others” are. The most effective feedback was when the referent household was from the same neighborhood as the individuals and its members were not identified.

Categorical induction from uncertain premises: Jeffrey's doesn't completely rule

Studies of categorical induction typically examine how belief in a premise (e.g., Falcons have an ulnar artery) projects on to a conclusion (e.g., Robins have an ulnar artery). We study induction in cases in which the premise is uncertain (e.g., There is an 80% chance that falcons have an ulnar artery). Jeffreys rule is a normative model for updating beliefs in the face of uncertain evidence. In three studies we tested the descriptive validity of Jeffreys rule and a related probability theorem, the rule of total probability. Although these rules provided good approximations to mean judgments in some cases, the results from regression and correlation analyses suggest that participants focus on the parts of these rules that are associated with the highest overall probability. We relate our findings to rational models of judgment.

Loss aversion and hypoxia: less loss aversion in oxygen-depleted environment

Abstract Hypoxia, the deprivation of adequate oxygen supply, constitutes a direct threat to survival by disrupting cardiovascular or respiratory homeostasis and eliciting a respiratory distress. Although hypoxia has been shown to increase brain vulnerability and impair basic cognitive functions, only one study has examined its effect on decision-making. The present study examined the effect of mild hypoxia on individual’s loss aversion, that is, the tendency to be more affected by losses than equal sized gains. A sample of 26 participants were asked to either accept or reject a series of mixed gambles once in an oxygen-depleted environment (14.1% oxygen concentration) and once in a normoxic environment (20.9% oxygen concentration). Each gamble involved a 50–50 chance of winning or losing specified amounts of money. Mild hypoxia decreased loss aversion: on average in the normoxic condition participants accepted gambles if the gain was at least 2.4 times as large as the loss, whereas in the oxygen-depleted condition participants accepted gambles if the gain was at least 1.7 times as large as the loss. Mild hypoxia may push individuals to be less cautious in daily decisions that involve a trade-off between a gain and a loss.