Brain Mechanisms for Interpreting the Actions of Others From Biological-Motion Cues

ABSTRACT— Humans are an intensely social species. Our social abilities depend upon specialized brain systems for rapidly recognizing the faces of others, for interpreting the actions of others through an analysis of biological-motion cues, and for determining the emotional states of others via inspection of facial expression. Recent work has implicated the superior temporal sulcus (STS) region as an important component of the social brain. Functional neuroimaging studies have provided clues about how this region is involved in the visual analysis and interpretation of other people's actions. STS activity is modulated by the context within which the actions of biological entities are observed. Such a contextual influence is consistent with a broader tradition within social psychology emphasizing the powerful influences of situational and contextual factors on behavior and perception. The STS region also shows promise as a region of importance in the investigation of both typical and impaired social-cognitive development. Future work should aim to inform us better of the development of interrelationships between the STS region and other regions of the social brain, including the amygdala and the fusiform gyrus.     

Rule-based and exemplar-based classification in artificial grammar learning

In this study, we examined the induction of syntactic rules, given the presentation of letter strings generated from a finite-state grammar. Our primary interest was whether application of abstracted syntax or analogy to remembered exemplars could serve as a basis for judgments of grammaticality of novel stimuli. The grammatical status of test items and their objective similarity to studied exemplars were manipulated independently to investigate whether rule-based or instance-based information was a more important determinant of classification performance. When group data were examined, the results indicated that both factors were equally important in influencing grammaticality judgments about novel letter strings. There were, however, large individual differences in the magnitude of grammatical status effects, with a subgroup of subjects clearly using a classification strategy other than analogy to remembered exemplars. The results offer qualified support for the hypothesis (Reber & Allen, 1978) that rule-based information can be implicitly abstracted given limited experience with richly structured stimulus domains, and these results are inconsistent with a strong version of the instance-based model of categorization.     

Electrooculographic indices of changes in simulated flying performance

Recent investigations have revealed statistically reliable relationships between signal detection by human subjects performing vigilance tasks and changes in the electrophysiologically recorded waveform of the eyeblink. Thus, this relatively simple and easy-to-obtain measure may have potential use as a predictor of impaired performance. This report describes a study in which eyeblink data were recorded on analog tape while subjects (instrument-rated pilots) “flew” a computer-generated flight plan in a General Aviation Trainer (GAT-1). Eyeblink data were reduced and scored with an adaptation of software from the Washington University Behavioral Research Laboratory. Subjects’ “flying” performance was evaluated with the Pilot Performance Evaluating System (PPES) implemented on a Digital Equipment Corporation (DEC), PDP-11/34 computer. The PPES samples each of four primary flight instruments once per second. It scores performance by generating a combined error score for each maneuver it assigns on the flight-plan display in the cockpit. The PPES/GAT-1 linkup has proved to be a valuable research tool with which to realistically evaluate stress effects and physiological correlates of flying performance in a laboratory setting. This study examined the relationships between eyeblink and flying performance scores collected during a pilot-fatigue study. Analysis of the data supports the use of computers cored eye movement measures as predictors of flying performance decrements.     

The gender-stereotyped nature of christmas toys received by 36-, 48-, and 60-month-old children: A comparison between nonrequested vs requested toys

This research provides normative information on the gender-stereotyped nature of Christmas toys that children received from their parents. A list of over 500 toys was obtained from the parents of 86 children between the ages of 31 and 65 months. The toys were rated and placed into gender-stereotyped groups, and were categorized into child requested or nonrequested groups. It was found that the children had considerable input into the types of toys they received from their parents for Christmas, requesting approximately one half of the toys. Toys the children requested were judged to be more gender stereotyped than nonrequested toys. Very few boys received either requested or nonrequested toys considered stereotyped for the opposite sex. In contrast, one third of the girls received at least one toy judged to be stereotyped for the opposite sex. Also, boys appeared to develop sex-typed interests in toys at an earlier age than girls, and they requested 72%, 76%, and 75% gender-stereotyped toys in the corresponding age groups of 36-, 48-, and 60-months. The girls' sex-typed interests in toys lagged behind the boys', with girls requesting 29%, 51%, and 73% gender-stereotyped toys for the same age groups. In the nonrequested condition, parents selected types of toys judged to be traditionally more sex role neutral and emphasized musical instruments, art supplies, and educational toys for their sons and educational toys for their daughters.     

Aphasia for Morse code

The ability to communicate by Morse code at high speed has, to our knowledge, not been localized within the cerebral cortex, but might be suspected as residing within the left (dominant) hemisphere. We report a case of a 54-year-old male who suffered a left temporal tip intracerebral hematoma and who temporarily lost his ability to communicate in Morse code, but who was minimally aphasic.     

Waning of panic sensations during prolonged hyperventilation

Recent theories about panic emphasize that a hyperventilatory positive feedback loop is involved in panic: catastrophic misinterpretation of bodily sensations may trigger anxiety, anxiety may stimulate hyperventilation, hyperventilation may promote the salience of feared sensations etc. Such models leave unexplained how and when panics come to an end. It was hypothesised that panic with hyperventilation may end because pronounced hyperventilation becomes, in the course of time, less powerful in generating perceivable bodily sensations. Twenty healthy subjects hyperventilated forcefully and experienced clear panic symptoms as defined by DSM IIIR. When pCO2 was kept 55% below base line for 90 min, panic symptoms waned. The mean intensity of the symptoms declined as did the number of symptoms occurring. No panic symptoms were observed in the control group (n = 20) who ventilated normally. In so far as hyperventilation is involved in the positive feedback loops that characterize panic, panic attacks may be time-limited because sensations induced by hyperventilation become less salient even if massive hyperventilation continues. As to the explanation of the reported phenomenon, it is suggested that, apart from habituation, local physiological changes due to prolonged hyperventilation may produce a decrease in interoceptive input.     

Habituation to irrelevant speech: effects on a visual short-term memory task

The Baddeley and Hitch (1974) formulation of short-term or working memory embodied a phonological store within the articulatory loop component of the model. Later formulations specifically postulated an acoustic filter that endowed only speech-like stimuli with obligatory access to this phonological store. This paper presents evidence that this phonological store may have two filters, one of which is subject to habituation and can therefore attenuate the entry of irrelevant speech, thus undermining the obligatory access assumption of the model. An experiment is reported in which subjects were presented with a habituation period comprising 20 min of irrelevant speech--speech to be ignored by the subject--before a test phase in which a visually presented serial recall task with concurrent irrelevant speech was performed. The effect of irrelevant speech, which impairs performance on the primary task when there is no habituation phase, is reduced markedly in those conditions where the speech used in the habituation phase is the same as that used in the test phase, if the irrelevant speech is in a language different from that presented during the subsequent trials or if the habituator is a hummed version of the irrelevant speech passage. When a nonspeech sound (pink noise) is used in the habituation phase, a large irrelevant speech effect is found in the test phase. Morris, Quayle, and Jones (1989) found that humming did not produce an irrelevant speech effect, which suggests that the first filter is permeable to humming but that the second filter is not.(ABSTRACT TRUNCATED AT 250 WORDS)     

Knowledge and the regularity theory of information

Fred Dretske's Knowledge and the Flow of Information is an extended attempt to develop a philosophically useful theory of information. Dretske adapts central ideas from Shannon and Weaver's mathematical theory of communication, and applies them to some traditional problems in epistemology. In doing so, he succeeds in building for philosophers a much-needed bridge to important work in cognitive science. The payoff for epistemologists is that Dretske promises a way out of a long-standing impasse — the Gettier problem. He offers an alternative model of knowledge as information-based belief, which purports to avoid the problems justificatory accounts face. This essay looks closely at Dretske's theory. I argue that while the information-theoretic framework is attractive, it does not provide an adequate account of knowledge. And there seems to be no way of tightening the theory without introducing some version of a theory of justification — the very notion Dretske's theory was designed to avoid.     

In search of the point of no return: the control of response processes

Control processes underlying response inhibition were examined. Six Ss performed a visual choice reaction task and were occasionally presented with a tone that told them to withhold the response. Reaction time results were in agreement with a model that assumes a race between response activation and response inhibition processes. Event-related brain potentials, electromyogram, and continuous response measures showed that responses could be interrupted at any time. Evidence was obtained for two inhibitory mechanisms: inhibition of central activation processes and inhibition of transmission of motor commands from central to peripheral structures. Results have implications for the distinction between controlled and ballistic processes.