Strength of scopolamine-induced amnesia as a function of time between training and testing

Variations in the strength of scopolamine-induced amnesia as a function of age of the habit were studied in Swiss Webster mice. Animals were trained in an active avoidance task to a criterion of 9/10 avoidances and immediately following training injected with scopolamine hydrochloride (1.0 mg/kg) or saline. Retention of the avoidance learning was evaluated by testing different groups of animals 1, 3, 7, 10, 14, and 28 days following training. The retention test consisted of five trials in which the CS but not the UCS was presented. Results indicated that saline-treated mice exhibited near-perfect retention up to 14 days post-training with forgetting beginning to be apparent at 28 days. Scopolamine treatment produced strong amnesia in animals tested 1 and 3 days post-training but normal retention in animals tested 7 and 10 days after learning. The amnesia abruptly reappeared at 14 days after which time it remained stable. The marked similarity of the scopolamine retention curve to changes in the strength of memory of discrimination learning in undertrained rats reported by Deutsch suggested that scopolamine resulted in the storage of a weak memory of the avoidance response. To explore this idea further we trained mice to a criterion (4/5) which would result in a weak avoidance response and tested different groups 1, 3, 10, 14, and 28 days following learning. Results showed that strength of the memory of avoidance learning increased up to 10 days and then decreased abruptly at 14 days thus replicating the general shape of the retention curve produced by injecting scopolamine following strong training. These data suggest that scopolamine disrupts processes essential for the formation of durable memories.     

Hierarchical classes: Model and data analysis

A discrete, categorical model and a corresponding data-analysis method are presented for two-way two-mode (objects × attributes) data arrays with 0, 1 entries. The model contains the following two basic components: a set-theoretical formulation of the relations among objects and attributes; a Boolean decomposition of the matrix. The set-theoretical formulation defines a subset of the possible decompositions as consistent with it. A general method for graphically representing the set-theoretical decomposition is described. The data-analysis algorithm, dubbed HICLAS, aims at recovering the underlying structure in a data matrix by minimizing the discrepancies between the data and the recovered structure. HICLAS is evaluated with a simulation study and two empirical applications.This research was supported in part by a grant from the Belgian NSF (NFWO) to Paul De Boeck and in part by NSF Grant BNS-83-01027 to Seymour Rosenberg. We thank Iven Van Mechelen for clarifying several aspects of the Boolean algebraic formulation of the model and Phipps Arabie for his comments on an earlier draft.     

Above suspicion: Cognitive and intentional aspects of the ability to lie

This paper looks at the attribution of the ability to lie and not at lying or lies. It also departs from more familiar approaches by focussing on the appraisal of an ability and not on the ability in itself. We believe that this attribution perspective is required to bring out the cognitive and intentional basis of the ability to lie.     

Local and global contextual constraints on the identification of objects in scenes.

Objects likely to appear in a given real-world scene are frequently found to be easier to recognize. Two different sources of contextual information have been proposed as the basis for this effect: global scene background and individual companion objects. The present paper examines the relative importance of these two elements in explaining the context-sensitivity of object identification in full scenes. Specific sequences of object fixations were elicited during free scene exploration, while fixation times on designated target objects were recorded as a measure of ease of target identification. Episodic consistency between the target, the global scene background, and the object fixated just prior to the target (the prime), were manipulated orthogonally. Target fixation times were examined for effects of prime and background. Analyses show effects of both factors, which are modulated by the chronology and spatial extent of scene exploration. The results are discussed in terms of their implications for a model of visual object recognition in the context of real-world scenes.