In the “Libet experiment” the onset of movement-related brain activity preceded the reported time of the conscious intention to move, suggesting that conscious intention may not play a role in initiating voluntary movements (Libet, Gleason, Wright, & Pearl, 1983). Dominik et al. (2017) provided evidence that the intention reports employed in the Libet experiment, which Libet et al. (1983) found to precede movement reports, are invalid. In the study by Dominik et al., intention reports preceded movement reports only when participants had prior experience making movement reports. Individuals without such experience reported intention around the same time as movement. These findings suggest that Libet’s intention reports do not reflect experiences of intention, but, rather, inferences based on prior experience with movement reports. Our study replicated the core findings of Dominik et al. We argue that Libet’s intention reports are invalid and explore the phenomenology of intention in the Libet experiment. 相似文献
Unfamiliarity with movement may lead isolated chicks to respond aggressively when tested with live, moving conspecifics. This hypothesis was tested by comparing the number and locus of pecks by isolated chicks to a stationary or moving model of a chick, and to a live chick. In a second test of the hypothesis chicks that viewed a moving object during isolation and chicks isolated without movement were tested with a live con-specific and their number and locus of pecks were compared. Neither experiment supported the hypothesis. Movement alone failed to excite aggressive pecks and prior experience with movement failed to suppress aggressive pecks. In the first experiment imlated chicks treated the live testmate more aggressively than the moving or stationary model. In the second experiment aggressive pecking of chicks was unaffected by prior experience with movement, These fmdmgs do not support the hypothesis that movement excites aggression in isolated chicks. Nonetheless the results focus attention on the generally neglected problem of emotional and motivational states produced by isolation. 相似文献
Integrity of both cerebral hemispheres is required to control in-phase or anti-phase coupling of ipsilateral hand and foot oscillations, as shown by the impairment of these tasks when performed on the healthy side of hemiplegic patients. On this basis, coupling of hand–foot movements was analysed in a right-handed subject (ME) who underwent a total resection of the corpus callosum. Oscillations of the prone hand and foot, paced by a metronome at different frequencies, as well as EMG activity in extensor carpi radialis (ECR) and tibialis anterior (TA) muscles were analysed by measuring the average phase difference between the hand and foot movements and EMG cycles.
ME performed in-phase movements (right-hand extension coupled to right-foot dorsal flexion) at frequencies up to 3 Hz, though the hand cycle progressively lagged the foot cycle as the frequency increased. At 3 Hz the hand lag reached −142° (as compared to about 25° in healthy subjects). The lag increased even further after application of an inertial load to the hand, reaching 180° at 1.8 Hz (about 50° in healthy subjects). ME's hand lag is caused by the lack of any anticipatory reaction in hand movers. In contrast to healthy subjects, which activate the ECR earlier than the TA when the frequency increases, ME activated the ECR later than TA at all frequencies higher than 0.9 Hz.
Anti-phase movements (hand extension coupled to foot plantar flexion) were performed only upto 1 Hz in unloaded conditions. At 0.6 Hz, movements were in tight phase-opposition (3°), but at 1 Hz, the hand lag reached −34° because of a delayed ECR activation. After hand loading ME was unable to couple movements in anti-phase. In contrast, normal subjects maintain a tight anti-phase coupling up to 2.0 Hz, both with an unloaded or loaded hand. Similar deficits were observed by ME when performing in-phase and anti-phase coupling on the left side, as well as when he was blindfolded.
In normal subjects, an anticipated muscular activation of hand movers compensates for hand loading. Since this compensation must depend on monitoring the hand delay induced by loading, the absence in ME of such compensatory reaction suggests that callosal division had apparently compromised the mechanisms sustaining feedback compensation for differences in the biomechanical limb properties. They also confirm and reinforce the idea that elaboration of the afferent message, aiming at controlling the phase of the movement association, needs the co-operation of both cerebral hemispheres. 相似文献
Three chimpanzees performed a computerized matching-to-sample task in which samples were photographs of items and comparison stimuli were geometric symbols called lexigrams. In Experiment 1, samples were either defined (i.e., they represented items that were associated already with a specific lexigram label by the chimpanzees) or undefined (i.e., they did not have an already learned association with a specific lexigram). On each trial, the foil (incorrect) comparison could be either a defined or an undefined lexigram. All 3 chimpanzees selected the correct comparison for undefined samples at a level significantly better than chance only when the foil comparison was defined. In Experiment 2, three comparisons were presented on each trial, and in Experiment 3, four comparisons were presented on each trial. For Experiments 2 and 3, the foil comparisons consisted of either defined or undefined comparisons or a mixture of both. For these two experiments, when the chimpanzees were presented with an undefined sample, they typically made selections of only undefined comparisons. These data indicate that the chimpanzees responded through use of exclusion. A final experiment, however, indicated that, despite the use of exclusion to complete trials with undefined samples correctly, the chimpanzees did not learn new associations between undefined samples and comparisons. 相似文献
Two experiments are reported which examine children's ability to use referential context when making syntactic choices in language production and comprehension. In a recent on-line study of auditory comprehension, Trueswell, Sekerina, Hill, and Logrip (1999) examined children's and adults' abilities to resolve temporary syntactic ambiguities involving prepositional phrases (e.g., “Put the frog on the napkin into ¨”). Although adults and older children used the referential context to guide their initial analysis (pursuing a destination interpretation in a one-frog context and a modifier interpretation in a two-frog context), 4 to 5-year olds' initial and ultimate analysis was one of destination, regardless of context. The present studies examined whether these differences were attributable to the comprehension process itself or to other sources, such as possible differences in how children perceive the scene and referential situation. In both experiments, children were given a language generation task designed to elicit and test children's ability to refer to a member of a set through restrictive modification. This task was immediately followed by the “put” comprehension task. The findings showed that, in response to a question about a member of a set (e.g., “Which frog went to Mrs. Squid's house?”), 4- to 5-year-olds frequently produced a definite NP with a restrictive prepositional modifier (e.g., “The one on the napkin”). These same children, however, continued to misanalyze put instructions, showing a strong avoidance of restrictive modification during comprehension. Experiment 2 showed that an increase in the salience of the platforms that distinguished the two referents increased overall performance, but still showed the strong asymmetry between production and comprehension. Eye movements were also recorded in Experiment 2, revealing on-line parsing patterns similar to Trueswell et al.: an initial preference for a destination analysis and a failure to revise early referential commitments. These experiments indicate that child–adult differences in parsing preferences arise, in part, from developmental changes in the comprehension process itself and not from a general insensitivity to referential properties of the scene. The findings are consistent with a probabilistic model for uncovering the structure of the input during comprehension, in which more reliable linguistic and discourse-related cues are learned first, followed by a gradually developing ability to take into account other more uncertain (or more difficult to learn) cues to structure. 相似文献
Studies in East European Thought - Articulated in the twenties, the doctrines of the exiled Russian ‘Evrazijstvo’ movement are undergoing a renaissance in Russia today. As the... 相似文献