A New Normalization Strategy for the Implicational Fragment of Classical Propositional Logic

The introduction and elimination rules for material implication in natural deduction are not complete with respect to the implicational fragment of classical logic. A natural way to complete the system is through the addition of a new natural deduction rule corresponding to Peirce’s formula (((A → B) → A) → A). E. Zimmermann [6] has shown how to extend Prawitz’ normalization strategy to Peirce’s rule: applications of Peirce’s rule can be restricted to atomic conclusions. The aim of the present paper is to extend Seldin’s normalization strategy to Peirce’s rule by showing that every derivation Π in the implicational fragment can be transformed into a derivation Π′ such that no application of Peirce’s rule in Π′ occurs above applications of →-introduction and →-elimination. As a corollary of Seldin’s normalization strategy we obtain a form of Glivenko’s theorem for the classical {→}-fragment.     

Thinking groups: Rhetorical enactment of collective identity in three Israeli Kibbutzim

The present paper reports a case study about public deliberations in three Israeli kibbutzim regarding a disputed school issue: whether to maintain a traditional in-kibbutz high school despite a heavy financial burden or to close it and send kibbutz youths to a public regional school The results served as a demonstration of a 'thinking group' (i.e. of how the collective aims of a group are achieved by the coordinated rhetorical behaviour of individuals according to the formal rules of the collective deliberations). First, video-recordings of six general assembly meetings in which the issue was discussed was analyzed as to their argumentative content. Second, the extracted arguments were presented to a sample of 342 kibbutz members to capture the distribution of opinions in the population. It is proposed that most kibbutz members were willing to preserve their collective living and saw the closure of their in-kibbutz school as a threat to their traditional collective identity. We observed a distinct form of public rhetoric during the deliberations in the general meetings which provides a podium for the disputed opinions, preserves the kibbutz shared identity representation and avoids social friction.     

Overcoming suppression in order to remember: Contributions from anterior cingulate and ventrolateral prefrontal cortex

The ability to remember is often compromised by competition from irrelevant memories. However, acts of selective remembering can alter the competitive relationship between memories; memories that are selected against are weakened, whereas those that are retrieved are strengthened. Whereas the weakening of selectedagainst memories is typically evidenced by subsequently poorer recall of these memories, the present study tested the hypothesis that when previously selected-against memories can subsequently be successfully retrieved, such acts of successful retrieval are associated with engagement of neurobiological mechanisms that serve to detect and overcome competition. Consistent with this hypothesis, fMRI revealed that anterior cingulate cortex and right ventrolateral prefrontal cortex are differentially engaged during successful retrieval of previously selected-against memories, and that their engagement is directly related to the magnitude of weakening that is induced by prior acts of selecting against these memories.     

Conformity effects in memory as a function of group size,dissenters and uncertainty

In two experimental studies we investigated how false memory reports provided by anonymous group members affect individuals' recognition. Participants were presented with a series of salient and non‐salient objects and recognition memory was subsequently assessed for presented and non‐presented stimuli. In this recognition test, participants were confronted with (in)correct responses from bogus group members. The findings indicate that the bogus answers influenced memory reports only in the absence of a clear recollection and if the stimulus was not judged to be particularly memorable. Moreover, we found no evidence that motivational influences affected participants' judgements. However, the influence of the bogus group decreased with the presence of dissenters who broke the unanimity of the group, and it increased with higher uncertainty. Copyright © 2002 John Wiley & Sons, Ltd.     

Adaptive skills and executive function in autism spectrum disorders.

There is active debate regarding the nature of executive dysfunction in autism. Additionally, investigations have yet to show a relationship between deficits in executive function and the everyday behavioral difficulties that may originate from them. The present study examined the relationship between executive abilities and adaptive behavior in 35 children with Autism Spectrum Disorders, using two parent reports of everyday functioning, the Vineland Adaptive Behavior Scales (VABS) and the Behavior Rating Inventory of Executive Function (BRIEF). Results found several relationships: The Initiate and Working Memory domains were negatively correlated with most domains of adaptive behavior. Also, the Communication and Socialization domains of the VABS were negatively correlated with several areas of executive functioning, suggesting that impairments in executive abilities are strongly associated with the deficits in communication, play and social relationships found in children with autism.     

Posterior parietal cortex and episodic retrieval: Convergent and divergent effects of attention and memory

Functional neuroimaging studies of humans engaged in retrieval from episodic memory have revealed a surprisingly consistent pattern of retrieval-related activity in lateral posterior parietal cortex (PPC). Given the well-established role of lateral PPC in subserving goal-directed and reflexive attention, it has been hypothesized that PPC activation during retrieval reflects the recruitment of parietal attention mechanisms during remembering. Here, we evaluate this hypothesis by considering the anatomical overlap of retrieval and attention effects in lateral PPC. We begin by briefly reviewing the literature implicating dorsal PPC in goal-directed attention and ventral PPC in reflexive attention. We then discuss the pattern of dorsal and ventral PPC activation during episodic retrieval, and conclude with consideration of the degree of anatomical convergence across the two domains. This assessment revealed that predominantly divergent subregions of lateral PPC are engaged during acts of episodic retrieval and during goal-directed and reflexive attention, suggesting that PPC retrieval effects reflect functionally distinct mechanisms from these forms of attention. Although attention must play a role in aspects of retrieval, the data reviewed here suggest that further investigation into the relationship between processes of attention and memory, as well as alternative accounts of PPC contributions to retrieval, is warranted.Episodic memory—declarative memory for events—has long been known to depend on the medial temporal lobe and, to a lesser extent, the prefrontal cortex (Squire 1992; Shimamura 1995; Wheeler et al. 1995; Gabrieli 1998; Eichenbaum and Cohen 2001; Squire et al. 2004). Recently, an explosion of functional neuroimaging studies has revealed that episodic retrieval is also consistently associated with activity in lateral posterior parietal cortex (PPC), including in the intraparietal sulcus and inferior parietal lobule (Figs. 1, ​,2;2; for detailed review, see Wagner et al. 2005; Cabeza 2008; Cabeza et al. 2008; Ciaramelli et al. 2008; Vilberg and Rugg 2008b; Olson and Berryhill 2009). This unexpected finding raises the possibility that parietal mechanisms may be more central to episodic retrieval than previously thought.Open in a separate windowFigure 1.Anatomy of posterior parietal cortex (PPC). A posterior-lateral view of human PPC is depicted, with PPC separated into dorsal and ventral portions by the intraparietal sulcus (IPS). Dorsal PPC includes the superior parietal lobule (SPL) and IPS. Ventral PPC includes inferior parietal lobule (IPL) and its subregions: supramarginal gyrus (SMG), temporoparietal junction (TPJ), and angular gyrus (AnG).Open in a separate windowFigure 2.Left lateral PPC activity during episodic retrieval. (A) A comparison of hits relative to correct rejections reported by Kahn et al. (2004) revealed “old/new” effects in dorsal PPC, inclusive of IPS. Average signal change within IPS was greater for items perceived as old (hits and false alarms) vs. those believed to be new (misses and correct rejections). (B) A comparison of successful, relative to unsuccessful, cued recall by Kuhl et al. (2007) revealed greater activity in AnG, compatible with the broader literature on recollection success effects (see Fig. 4). In addition, effects were observed in more anterior aspects of ventral PPC (SMG), as well as in dorsal PPC (principally SPL) (see Discussion). (C) Orienting to memory in attempts to recollect, independent of recollection success, is often associated with activity in dorsal PPC. For example, comparison of temporal recency judgments to novelty-based decisions elicited greater IPS activity (Dudukovic and Wagner 2007).At the neuropsychological level, human lesion evidence regarding the necessity of lateral PPC mechanisms for episodic retrieval is limited and mixed (Berryhill et al. 2007; Davidson et al. 2008; Haramati et al. 2008; Simons et al. 2008). By contrast, other neuropsychological data indicate that lateral PPC is unambiguously associated with another cognitive domain—attention (Posner et al. 1984; Mesulam 1999; Parton et al. 2004). This latter lesion literature is further complemented by rich functional neuroimaging evidence implicating dorsal and ventral PPC in goal-directed and reflexive attention, respectively (for review, see Corbetta and Shulman 2002; Corbetta et al. 2008).Drawing from the rich literature linking attention to lateral PPC, memory researchers have recently proposed that lateral PPC activity during episodic retrieval tasks reflects the engagement of attention mechanisms during remembering (Cabeza 2008; Cabeza et al. 2008; Ciaramelli et al. 2008; Olson and Berryhill 2009). Specifically, it has been hypothesized that: (1) Dorsal PPC activity during retrieval may reflect the recruitment of goal-directed attention in service of performing retrieval tasks and (2) ventral PPC engagement during retrieval may mark the reflexive capture of attention by mnemonic representations. While prior comprehensive reviews of the neuroimaging literature on parietal correlates of episodic retrieval have documented functional dissociations along the dorsal/ventral axis of lateral PPC, which qualitatively parallel those seen in the attention literature, evaluation of the hypothesis that PPC retrieval activity reflects attention mechanisms further requires an assessment of the degree to which attention and retrieval effects co-localize. Here we review lateral PPC correlates of both episodic retrieval and attention, with the goal of directly assessing to the degree of anatomic overlap.It should be noted from the outset that the aim of the present review is to evaluate the hypothesis that lateral PPC episodic retrieval effects can be explained in terms of goal-directed and reflexive attention mechanisms. As such, we a priori imposed three constraints that served to focus our treatment of these two substantial literatures. First, while both the dual-attention and memory retrieval literatures focus on effects on the lateral parietal surface, retrieval effects are predominantly left lateralized. Thus, we constrained our analysis of attention and retrieval findings to left lateral PPC.⁵ Second, because prior retrieval reviews focused theoretical discussion on dual-attention accounts, here we similarly constrained our treatment of the extensive attention literature to include only those effects relevant to dual-attention theory. Finally, because the preponderance of evidence offered in support of dual-attention theory''s proposed dorsal attention network derives from studies of visual attention, the present review of the dorsal network is also confined to visual attention. As such, the present review should not be viewed as a comprehensive review of the entire attention literature.We first survey the functional neuroimaging literature on parietal correlates of goal-directed and reflexive attention, and then discuss how these correlates converge and diverge with the patterns of lateral PPC activity present during episodic retrieval. We conclude by considering theoretical frameworks that focus on the role of attention in episodic retrieval, as well as nonattention-based accounts of PPC activity during retrieval, and we highlight open questions that await further investigation.     

EFFECTS OF RESPONSE SPACING ON ACQUISITION AND RETENTION OF CONDITIONAL DISCRIMINATIONS

Pigeons were exposed to a repeated acquisition procedure in which no delays were imposed and rate of responding was relatively high. They also were exposed to conditions in which delays were arranged between trials within chains or between completed chains, and rates of responding were lower. Number of trials, rate of reinforcement, difficulty of the discrimination, and motivating operations were held constant. Terminal accuracy was highest under the no‐delay condition, in which rate of responding was highest. Effects of trial spacing on retention were mixed and depended on whether delays were imposed between trials within chains or between completed chains. These findings provide basic‐research support for the rapid presentation of trials in direct instruction and for rate building in precision teaching.     

Embodied communication: Speakers’ gestures affect listeners’ actions

We explored how speakers and listeners use hand gestures as a source of perceptual-motor information during naturalistic communication. After solving the Tower of Hanoi task either with real objects or on a computer, speakers explained the task to listeners. Speakers’ hand gestures, but not their speech, reflected properties of the particular objects and the actions that they had previously used to solve the task. Speakers who solved the problem with real objects used more grasping handshapes and produced more curved trajectories during the explanation. Listeners who observed explanations from speakers who had previously solved the problem with real objects subsequently treated computer objects more like real objects; their mouse trajectories revealed that they lifted the objects in conjunction with moving them sideways, and this behavior was related to the particular gestures that were observed. These findings demonstrate that hand gestures are a reliable source of perceptual-motor information during human communication.