This article questions the rather pessimistic conclusions of Allen and Carroll [Macroeconomic Dynamics 5 (2001), 255–271] about the ability of consumers to learn the optimal buffer-stock-based consumption rule. To this end, we develop an agent-based model in which alternative learning schemes can be compared in terms of the consumption behavior that they yield. We show that neither purely adaptive learning nor social learning based on imitation can ensure satisfactory consumption behavior. In contrast, if the agents can form adaptive expectations, based on an evolving individual mental model, their behavior becomes much more interesting in terms of its regularity and its ability to improve performance (which is a clear manifestation of learning). Our results indicate that assumptions on bounded rationality and on adaptive expectations are perfectly compatible with sound and realistic economic behavior, which, in some cases, can even converge to the optimal solution. This framework may therefore be used to develop macroeconomic models with adaptive dynamics.

Core social interaction behaviors were examined in young children 0–36 months of age who were hospitalized for accidental (n = 61) or inflicted (n = 64) traumatic brain injury (TBI) in comparison to typically developing children (n = 60). Responding to and initiating gaze and joint attention (JA) were evaluated during a semi-structured sequence of social interactions between the child and an examiner at 2 and 12 months after injury. The accidental TBI group established gaze less often and had an initial deficit initiating JA that resolved by the follow-up. Contrary to expectation, children with inflicted TBI did not have lower rates of social engagement than other groups. Responding to JA was more strongly related than initiating JA to measures of injury severity and to later cognitive and social outcomes. Compared to complicated-mild/moderate TBI, severe TBI in young children was associated with less responsiveness in social interactions and less favorable caregiver ratings of communication and social behavior. JA response, family resources, and group interacted to predict outcomes. Children with inflicted TBI who were less socially responsive and had lower levels of family resources had the least favorable outcomes. Low social responsiveness after TBI may be an early marker for later cognitive and adaptive behavior difficulties. (JINS, 2013, 19, 1–11)

Post-error slowing (i.e., slowing of a response on correct trials following an error) is thought to reflect adaptive behavior that may be impaired in Attention-Deficit/Hyperactivity Disorder (ADHD). The current study examined post-error slowing in children with ADHD and typically developing controls on two cognitive tasks. Fifty-one ADHD-Combined type, 53 ADHD-Inattentive type, and 47 controls completed a Choice Discrimination and Stop Signal Task with incentive and event rate manipulations. Linear mixed models were used to examine reaction times surrounding errors (trial-by-trial). Pre-error speeding and pre- to post-error slowing occurred on both tasks. Impaired post-error slowing was only present on the Choice Discrimination Task for the ADHD-Inattentive type. Post-error slowing is impaired in children with ADHD-Inattentive type, but not ADHD-Combined type, on a simple attention task. These findings highlight the importance of considering task demands and ADHD subtype when examining post-error slowing and also provide a novel approach to quantifying post-error slowing. (JINS, 2012, 18, 612–617)

Axel Leijonhufvud made an enormous impact on macroeconomics in the late 1960s with the publication of his book On Keynesian Economics and the Economics of Keynes: A Study of Monetary Economics (1968). In this famous book, Leijonhufvud argued that the standard neoclassical synthesis (Hicks–Hansen IS-LM) interpretation of the General Theory totally misunderstood and misinterpreted Keynes. However, during the 1970's, interest in Keynes and Keynesian models waned as new classical equilibrium models became all the rage. Nevertheless, Leijonhufvud, from a position outside the mainstream, continued his research into problems of unemployment, business cycles, and inflation—issues that from his perspective are problems of coordination failure in complex dynamical systems. Axel Leijonhufvud is currently Professor Emeritus at the University of California, Los Angeles, and, since 1995, Professor of Monetary Economics at the University of Trento, Italy. In this interview the author discusses with Leijonhufvud a wide range of issues relating to his own work as well as his views on the development of macroeconomics after Keynes.