Multiple cue use and integration in pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>)

Encoding multiple cues can improve the accuracy and reliability of navigation and goal localization. Problems may arise, however, if one cue is displaced and provides information which conflicts with other cues. Here we investigated how pigeons cope with cue conflict by training them to locate a goal relative to two landmarks and then varying the amount of conflict between the landmarks. When the amount of conflict was small, pigeons tended to integrate both cues in their search patterns. When the amount of conflict was large, however, pigeons used information from both cues independently. This context-dependent strategy for resolving spatial cue conflict agrees with Bayes optimal calculations for using information from multiple sources.     

Comparing the effects of low-level and high-level worker need-satisfaction: A synthesis of the self-determination and Maslow need theories

According to Maslow’s (Psychol Rev 50:370–396, 1943) hierarchical theory of needs, people do not become sensitized to “higher” level needs until they have satisfied their “lower” level needs (a moderator hypothesis); until then, they are unprepared to benefit from higher-level satisfactions. But according to the self-determination theory (SDT) model, high-level psychological needs, when met, are non-contingently beneficial (a main effect-only hypothesis). In two large-N studies of Russian energy companies, we measured low-level need-satisfaction in terms of felt security and felt financial satisfaction, and measured high-level need satisfaction in terms of SDT’s basic needs of autonomy, competence, and relatedness. In both studies, both the lower level and higher level need-satisfaction sets had strong main effects upon many positive work outcomes, including intrinsic motivation, organizational commitment, and SWB. In Study 2, Maslow’s “prepared to benefit” hypothesis was supported, in that satisfaction of high-level needs had slightly larger effects on outcomes when combined with satisfaction of low-level needs. However this was not found in Study 1. Potentials for integrating the SDT and Maslow need theories are discussed.     

Grammatical Encoding in Aphasia: Evidence from a “Processing Prosthesis”

Agrammatic aphasia is characterized by severely reduced grammatical structure in spoken and written language, often accompanied by apparent insensitivity to grammatical structure in comprehension. Does agrammatism represent loss of linguistic competence or rather performance factors such as memory or resource limitations? A considerable body of evidence supports the latter hypothesis in the domain of comprehension. Here we present the first strong evidence for the performance hypothesis in the domain of production: an augmentative communication system that markedly increases the grammatical structure of agrammatic speech while providing no linguistic information, functioning merely to reduce on-line processing demands. Copyright 2000 Academic Press and Unisys Corporation.     

Freedom,Frailty, and Impurity

The central question in Heidegger's philosophy, early and late, is that concerning the meaning of being. Recently, some have suggested that Heidegger himself interprets being to mean presence (Anwesen, Anwesenheit, Praesenz), citing as evidence lectures dating from the 1920s to the 1960s. I argue, on the contrary, that Heidegger regards the equation between being and presence as the hallmark of metaphysical thinking, and that it only ever appears in his texts as a gloss on the philosophical tradition, not as an expression of his own ontological commitments. In his early work Heidegger seeks to confront and even correct the traditional interpretation of being by challenging its narrow preoccupation with presence and the present. By the 1930s, however, he abandons the idea that there is anything to‐be intrinsically right or wrong about with regard to the meaning of being and turns his attention instead to what he calls ‘appropriation’ (Ereignis) or the truth of being, that is, the essentially ahistorical condition for the possibility of all historically contingent interpretations of being, including the metaphysical interpretation of being as presence.     

Enactive imagery in paired-associate learning

Three experiments were conducted to study the effects of enactive imagery (EI) on associative learning. In Experiment I, groups of Ss rated 226 verbs on EI and frequency. In Experiments II and III, Ss learned a 24- and a 16-item list, respectively. The lists consisted of the four possible stimulus-response combinations of high (H) and low (L) EI verb pairs: H-H, H-L, L-H, L-L. In both experiments, EI was found to be a significant factor on the stimulus side, performance being superior when the stimulus was of high EI. In Experiment III, the response EI main effect and the Stimulus by Response EI interaction were also found to be significant. The results indicated that like the imagery evoked by nouns, the EI evoked by verbs facilitates learning.     

Pigeons encode absolute distance but relational direction from landmarks and walls

In recent studies, researchers have examined animals' use of absolute or relational distances in finding a hidden goal. When trained with an array of landmarks, most animals use the default strategy of searching at an absolute distance from 1 or more landmarks. In contrast, when trained in enclosures, animals often use the relationship among walls. In the present study, pigeons were trained to find the center of an array of landmarks or a set of short walls that did not block external cues. Expansion tests showed that both groups of pigeons primarily used an absolute distance strategy. However, on rotational tests, pigeons continued to search in the center of the array, suggesting that direction was learned in relation to array.     

Stimulus generalization of behavioral history: Interspecies generality and persistence of generalization gradients

Four pigeons were exposed to a tandem variable-interval (VI) fixed-ratio (FR) schedule in the presence of a 50-pixel (about 15 mm) square or an 80-pixel (about 24 mm) square and to a tandem VI differential-reinforcement-of-low-rate (DRL) schedule when a second 80-pixel or 50-pixel square was present. The values of the VI and FR schedules were adjusted to equate reinforcement rates in the two tandem schedules. Following this, a square-size continuum generalization test was administered under a fixed-interval (FI) schedule or extinction. In the first testing session, response frequency was a graded function of the similarity of the test stimuli to the training stimuli for all pigeons. These systematic generalization gradients persisted longer under the FI schedule than under extinction.