Sharvy’s Lucy and Benjamin Puzzle

Sharvy’s puzzle concerns a situation in which common knowledge of two parties is obtained by repeated observation each of the other, no fixed point being reached in finite time. Can a fixed point be reached?     

Common knowledge of payoff uncertainty in games

Using epistemic logic, we provide a non-probabilistic way to formalise payoff uncertainty, that is, statements such as ‘player i has approximate knowledge about the utility functions of player j.’ We show that on the basis of this formalisation common knowledge of payoff uncertainty and rationality (in the sense of excluding weakly dominated strategies, due to Dekel and Fudenberg (1990)) characterises a new solution concept we have called ‘mixed iterated strict weak dominance.’     

服刑人员与普通民众价值取向的比较研究

目的：研究服刑人员价值取向的特点,以及与普通民众价值取向的差异。方法：使用中国民众价值取向调查问卷对242名服刑人员及131名普通民众进行测量。结果：服刑人员价值取向存在显著的婚姻状况、学历、年龄、犯罪历史、犯罪类型等方面的差异;与普通民众有差异。结论：服刑人员的价值取向不同于普通民众。     

The Contributing Factors of Change in a Therapeutic Process

The clients’ and therapists’ perceptions about the degree to which each of four common factors in therapy—extra-therapeutic factors; model/techniques; therapeutic alliance; and hope/expectancy—contribute to change in the therapeutic process were investigated in this study. In addition, the perceptions about the percentage of change attributed to clients and therapists were also explored. Results revealed that the therapists and clients have different perceptions on what factors contribute the most to change and that clients and therapists believe that the client contributes the most to change in a therapeutic process.M. L. Thomas, MSW, is a doctoral student in Marriage and Family Therapy at Florida State University.     

The Common Beliefs Survey-III, The Situational Self-Statement, and Affective State Inventory and Their Relationship to Authoritarianism and Social Dominance Orientation

The concept of irrational beliefs is central to rational emotive behavior therapy (REBT). These beliefs are defined by their absolutist and dogmatic qualities. The terms absolutist and dogmatic are also characteristic of some personality constructs, right-wing authoritarianism (RWA) being foremost among these. A relatively new personality construct, social dominance orientation (SDO) is similar to RWA in that both are excellent predictors of prejudice. As these two constructs are independent of each other, it has been suggested that they have different etiological underpinnings. The present study examined the relationship between the presence of irrational beliefs in people scoring high in RWA and SDO. Results suggest that high RWAs are more likely than high SDOs to endorse irrational beliefs. These findings add to the growing literature examining the relationship between these two personality constructs as well as suggesting possible implications for the use of REBT with clients scoring high on these personality dimensions.     

Knowing and Supposing in Games of Perfect Information

The paper provides a framework for representing belief-contravening hypotheses in games of perfect information. The resulting t-extended information structures are used to encode the notion that a player has the disposition to behave rationally at a node. We show that there are models where the condition of all players possessing this disposition at all nodes (under their control) is both a necessary and a sufficient for them to play the backward induction solution in centipede games. To obtain this result, we do not need to assume that rationality is commonly known (as is done in [Aumann (1995)]) or commonly hypothesized by the players (as done in [Samet (1996)]). The proposed model is compared with the account of hypothetical knowledge presented by Samet in [Samet (1996)] and with other possible strategies for extending information structures with conditional propositions. This research was funded by the National Science Foundation: “Game-Theoretic Foundation for Multi-Agent Systems”, IIS 9734923. Special Issue Formal Epistemology II. Edited by Branden Fitelson     

Perception of the stereokinetic illusion by the common marmoset (<Emphasis Type="Italic">Callithrix jacchus</Emphasis>)

Stereokinetic illusions have never been investigated in non-human primates, nor in other mammalian species. These illusions consist in the perception of a 3D solid object when certain 2D stimuli are rotated slowly in the plane perpendicular to the line of sight. The ability to perceive the stereokinetic illusion was investigated in the common marmoset (Callithrix jacchus). Four adult marmosets were trained to discriminate between a solid cylinder and a solid cone for food reward. Once learning criterion was reached, the marmosets were tested in sets of eight probe trials in which the two solid objects used at training were replaced by two rotating 2D stimuli. Only one of these stimuli produced, at least to the human observer, the stereokinetic illusion corresponding to the solid object previously reinforced. At test, the general behaviour and the total time spent by the marmosets observing each stimulus were recorded. The subjects stayed longer near the stimulus producing the stereokinetic illusion corresponding to the solid object reinforced at training than they did near the illusion corresponding to the previously non-rewarded stimulus. Hence, the common marmosets behaved as if they could perceive stereokinetic illusions.     

Conversation, gaze coordination, and beliefs about visual context

Conversation is supported by the beliefs that people have in common and the perceptual experience that they share. The visual context of a conversation has two aspects: the information that is available to each conversant, and their beliefs about what is present for each other. In our experiment, we separated these factors for the first time and examined their impact on a spontaneous conversation. We manipulated the fact that a visual scene was shared or not and the belief that a visual scene was shared or not. Participants watched videos of actors talking about a controversial topic, then discussed their own views while looking at either a blank screen or the actors. Each believed (correctly or not) that their partner was either looking at a blank screen or the same images. We recorded conversants' eye movements, quantified how they were coordinated, and analyzed their speech patterns. Gaze coordination has been shown to be causally related to the knowledge people share before a conversation, and the information they later recall. Here, we found that both the presence of the visual scene, and beliefs about its presence for another, influenced language use and gaze coordination.     

Superordinate identity and intergroup roommate friendship development

A common ingroup identity promotes positive attitudes and behavior toward members of outgroups, but the durability of these effects and generalizability to relationships outside of the laboratory have been questioned. The present research examined how initial perceptions of common ingroup identity among randomly assigned college roommates provide a foundation for the development of intergroup friendships. For roommate dyads involving students who differed in race or ethnicity, respondents who were low on perceived intergroup commonality showed a significant decline in friendship over-time, whereas those high on perceived commonality showed consistently high levels of friendship. Similarly, participants in these dyads demonstrated a significant decline in feelings of friendship when their roommate was low in perceived commonality but not when their roommate was high in perceived commonality. These effects were partially mediated by anxiety experienced in interactions over-time. The implications of a common identity for intergroup relationship development are discussed.     

Action–effect congruence during observational learning leads to faster action sequence learning

Common coding theory suggests that any action (pressing a piano key) is intimately linked with its resultant sensory effect (an auditory musical tone). We conducted two experiments to explore the effect of varying auditory action–effect patterns during complex action learning. In Experiment 1, participants were assigned to 1 of 4 groups, watched a silent video of a hand playing a sequence on a piano keyboard with no auditory action effect (observation) and were asked to practise and perform the sequence on an identical keyboard with varying action effects (reproduction). During reproduction, Group 1 heard no auditory tones (identical to observed video), Group 2 heard typical scale-ascending piano tones with each key press, Group 3 heard fixed but out-of-sequence piano tones with each key press, and Group 4 heard random piano tones with each key press. In Experiment two, new participants were assigned to 1 of 2 groups and watched an identical video; however, the video in this experiment contained typical, scale-ascending piano sounds. During reproduction, Group 1 heard no auditory tones while Group 2 heard typical, scale-ascending piano tones with each key press (identical to observed video). Our results showed that participants whose action–effect patterns during reproduction matched those in the observed video learned the action sequence faster than participants whose action–effect patterns during reproduction differed from those in the observed video. Additionally, our results suggest that adding an effect during reproduction (when one is absent during observation) is somewhat more detrimental to action sequence learning than removing an effect during reproduction (when one is present during observation).