Message Exchange Games in Strategic Contexts

When two people engage in a conversation, knowingly or unknowingly, they are playing a game. Players of such games have diverse objectives, or winning conditions: an applicant trying to convince her potential employer of her eligibility over that of a competitor, a prosecutor trying to convict a defendant, a politician trying to convince an electorate in a political debate, and so on. We argue that infinitary games offer a natural model for many structural characteristics of such conversations. We call such games message exchange games, and we compare them to existing game theoretic frameworks used in linguistics—for example, signaling games—and show that message exchange games are needed to handle non-cooperative conversation. In this paper, we concentrate on conversational games where players’ interests are opposed. We provide a taxonomy of conversations based on their winning conditions, and we investigate some essential features of winning conditions like consistency and what we call rhetorical cooperativity. We show that these features make our games decomposition sensitive, a property we define formally in the paper. We show that this property has far-reaching implications for the existence of winning strategies and their complexity. There is a class of winning conditions (decomposition invariant winning conditions) for which message exchange games are equivalent to Banach- Mazur games, which have been extensively studied and enjoy nice topological results. But decomposition sensitive goals are much more the norm and much more interesting linguistically and philosophically.     

Decision making and free will: a neuroscience perspective

A thorough analysis of the question of whether we possess "free will" requires that we take into account the process of exercising that will: that is, the neural mechanisms of decision making. Much of what we know about these mechanisms indicates that decision making is greatly influenced by implicit processes that may not even reach consciousness. Moreover, there exist conditions, for example certain types of brain injury or drug addiction, in which an individual can be said to have a disorder of the will. Examples such as these demonstrate that the idea of freedom of will on which our legal system is based is not supported by the neuroscience of decision making. Using the criminal law as an example, we discuss how new discoveries in neuroscience can serve as a tool for reprioritizing our society's legal intuitions in a way that leads us to a more effective and humane system.     

From early withdrawal reaction to infant depression: A baby alone does exist

Despite the frequent use of the term and although it is a key notion in evaluation, infant depression remains poorly defined and assessed since the initial work of René Spitz. This paper reviews recent aspects of infant depression related to classification, issues in infancy, attachment disorders, relationship disorders, maternal depression, failure to thrive and protein energy malnutrition. The actual scope of depression might include some aspects of protein energy malnutrition, a frequent and severe disease in tropical and developing countries, and some aspects of failure to thrive as observed in some multi-problem families in western countries. There might be a continuum between withdrawal reaction and infant depression. Withdrawal reaction is observed in various organic or psychopathological conditions, and could be used as an alarm symptom to screen infants in well-baby clinics. Infant depression is difficult to recognize, and delay in its recognition may have important developmental consequences. © 1997 Michigan Association for Infant Mental Health     

Know thyself: Metacognitive networks and measures of consciousness

Subjective measures of awareness rest on the assumption that conscious knowledge is knowledge that participants know they possess. Post-Decision Wagering (PDW), recently proposed as a new measure of awareness, requires participants to place a high or a low wager on their decisions. Whereas advantageous wagering indicates awareness of the knowledge on which the decisions are based, cases in which participants fail to optimize their wagers suggest performance without awareness. Here, we hypothesize that wagering and other subjective measures of awareness reflect metacognitive capacities subtended by self-developed metarepresentations that inform an agent about its own internal states. To support this idea, we present three simulations in which neural networks learn to wager on their own responses. The simulations illustrate essential properties that are required for such metarepresentations to influence PDW as a measure of awareness. Results demonstrate a good fit to human data. We discuss the implications of this modeling work for our understanding of consciousness and its measures.     

Sequential learning models for the Wisconsin card sort task: Assessing processes in substance dependent individuals

The Wisconsin card sort task (WCST) is a commonly used neuropsychological test of executive or frontal lobe functioning. Traditional behavioral measures from the task (e.g., perseverative errors) distinguish healthy controls from clinical populations, but such measures can be difficult to interpret. In an attempt to supplement traditional measures, we developed and tested a family of sequential learning models that allowed for estimation of processes at the individual subject level in the WCST. Testing the model with substance dependent individuals and healthy controls, the model parameters significantly predicted group membership, even when controlling for traditional behavioral measures from the task. Substance dependence was associated with (a) slower attention shifting following punished trials and (b) reduced decision consistency. Results suggest that model parameters may offer both incremental content validity and incremental predictive validity.     

Hemispatial neglect and serial order in verbal working memory

Working memory refers to our ability to actively maintain and process a limited amount of information during a brief period of time. Often, not only the information itself but also its serial order is crucial for good task performance. It was recently proposed that serial order is grounded in spatial cognition. Here, we compared performance of a group of right hemisphere-damaged patients with hemispatial neglect to healthy controls in verbal working memory tasks. Participants memorized sequences of consonants at span level and had to judge whether a target consonant belonged to the memorized sequence (item task) or whether a pair of consonants were presented in the same order as in the memorized sequence (order task). In line with this idea that serial order is grounded in spatial cognition, we found that neglect patients made significantly more errors in the order task than in the item task compared to healthy controls. Furthermore, this deficit seemed functionally related to neglect severity and was more frequently observed following right posterior brain damage. Interestingly, this specific impairment for serial order in verbal working memory was not lateralized. We advance the hypotheses of a potential contribution to the deficit of serial order in neglect patients of either or both (1) reduced spatial working memory capacity that enables to keep track of the spatial codes that provide memorized items with a positional context, (2) a spatial compression of these codes in the intact representational space.