Discrete vs. continuous processing: The fate of an incompletely processed perceptual dimension

A relevant issue in the debate on continuous vs. discrete processing of information is whether incompletely processed information does or does not affect a subsequent reaction. Two stimuli (SL, SR) were presented on eye level, subtending a visual angle of 45 degrees. SL was always inspected first, followed by a saccade to SR and finally by a same/different response. The fixation time of SL (TL), the saccadic time (TM) and the time from fixating SR to the response (TR) were separately measured. SL and SR consisted of two-dimensional stimuli (size and letter shape) constructed in such a way that encoding size took longer for one group and encoding shape took longer for another group of 10 subjects. All subjects were tested in three conditions: Shape was relevant in one, size in the second, and both dimensions were relevant in the third condition.

TL was less when encoding the relevant dimension was fast. When both dimensions were relevant, TL was about as long as when only the slow dimension was relevant, suggesting parallel and interference-free processing during TL. When only the slow dimension was relevant, TR (same) was much longer when the fast dimension differed. When the fast dimension was relevant, TR (same) was slightly longer when the slow dimension differed, which can be handled by either model. The experiment was repeated with three well-practiced and less variable subjects who carried out sufficient trials to measure TR as a function of TL. The results of this study were in line with the discrete model: A different slow and irrelevant dimension did not affect the same response regardless of the duration of TL. Interestingly, subjects were capable of retrieving the slow dimension, suggesting a code which can be used for retrieval but which does not affect the same/different response.     

Perception of signals presented in the periphery of the visual field

Two experiments were performed which tested the type of information that can be extracted from the periphery of the visual field, i.e. content information or position information. In both studies two digits were compared, one presented at the left and one at the right of the subject's meridian, seperated by a binocular visual angle, comprising either an eye-field (45°) or a head-field display (100°). In the first experiment the right signal was presented in separate blocks of either degraded or undegraded digits. In the case of undegraded digits, processing efficiency was better in the eye-field than in the head-field. With degraded digits this eye-field advantage was significantly smaller, but did not altogether disappear, suggesting that information about both the content and the position of digits in the periphery is acquired in the eye-field as opposed to the head-field. In the second experiment degraded and undegraded digits occured randomly within the same block of trials. This was done to investigate whether peripheral information is acquired automatically or through controlled processing. The results indicate a small eye-field advantage, about equal for both degraded and undegraded digits. This supports the controlled processing hypothesis, at least with regard to the acquisition of content information from the periphery.     

Electrophysiological responses to ethanol, pentobarbital, and nicotine in mice genetically selected for differential sensitivity to ethanol

Cortical electroencephalographic (EEG) changes induced by ethanol (4.3 and 1.4 g/kg, ip), pentobarbital (50 and 16 mg/kg), and nicotine (1.0 g/kg) were examined in long-sleep (LS) and short-sleep (SS) mice that were genetically selected for differential sleep times induced by a hypnotic dosage of ethanol. Ethanol (4.3 g/kg) caused EEG changes that paralleled the behavioral differences, whereas no differences between selected lines were observed following the activating dose (1.4 g/kg). Data support the notion that the known difference in ethanol sleep times is due not to greater SS sensitivity to ethanol activation but rather to greater LS sensitivity to ethanol hypnosis. No differences between selected lines were observed following 50 mg/kg pentobarbital, which again parallels previous behavioral data. The SS mice were more responsive to pentobarbital activation (16 mg/kg). Nicotine more severely reduced EEG power and heart rate in LS mice; a continuous iv infusion of nicotine elicited a distinct pattern of behavioral stereotypy for each selected line, with more profound motor and reflex depression in LS mice. The lines do not differ in rate of nicotine metabolism, hence they must differ in central nervous system sensitivity to nicotine. Thus, lines of mice selectively bred for differential sensitivity to ethanol also display marked differences in electrophysiological and behavioral responses to nicotine.     

A suppressing effect of response selection on immediate arousal in a choice reaction task

A clear conflict exists between experiments showing either additive or interactive effects of foreperiod duration and S-R compatibility on choice reaction time. It is hypothesized that in principle S-R compatibility and foreperiod duration have additive effects but that the effect of foreperiod duration is reduced in conditions where a signal is immediately arousing and where the S-R relations are highly compatible. In the case of low S-R compatibility the effect of immediate arousal is supposed to be ineffective.This hypothesis is tested and confirmed in an experiment in which the combined effects of foreperiod duration and S-R compatibility were studied with either loud (85 dBA) or weak (45 dBA) auditory signals. As predicted, additive effects were found in the latter case, while an interaction was observed with 85 dBA signals.     

Comprehension and production of the /−ez/ plural allomorph

Children's knowledge of morphological elements has traditionally been tested using Berko-type production tasks. Failure to respond correctly in this task may reflect production constraints independent of underlying linguistic knowledge. Accordingly, a detailed comparison of the comprehension of one morphological unit the /–ez/ plural allomorph, was investigated. Two groups of subjects were tested: (1) those who produced this allomorph correctly and (2) those who failed to produce it. For the subjects as a group, the results indicated that children who could produce the /–ez/ allomorph in nonsense word contexts performed significantly better than children who were unable to produce this allomorph. An analysis of individual performance indicated that almost all of the subjects who produced the /–ez/ allomorph correctly reliably comprehended it. A little more than half of the subjects who failed to produce it evidenced reliable comprehension. The conclusion was drawn that comprehension learning precedes production learning and that production-type tasks may consistently underestimate linguistic knowledge.This paper was supported by the Graduate College, University of Missouri, Kansas City.     

Pre- and postlexical loci of contextual effects on word recognition

The context in which a word occurs could influence either the actual decoding of the word or a postrecognition judgment of the relatedness of word and context. In this research, we investigated the loci of contextual effects that occur in lexical priming, when prime and target words are related along different dimensions. Both lexical decision and naming tasks were used because previous research had suggested that they are differentially sensitive to postlexical processing. Semantic and associative priming occurred with both tasks. Other facilitative contextual effects, due to syntactic relations between words, backward associations, or changes in the proportion of related items, occurred only with the lexical decision task. The results indicate that only associative and semantic priming facilitate the decoding of a target; the other effects are postlexical. The results are related to the different demands of the naming and lexical decision tasks, and to current models of word recognition.     

Adolescents' academic expectations and achievement

Previous research has indicated that adolescents' relationships with their mother influence their academic expectations and achievement. Substance use has also been found to have a strong influence on academic expectations and achievement. In the present study, 80 high school seniors from middle to upper socioeconomic status families completed questionnaires on behavioral and psychological aspects of adolescent life. Academic expectations were found to be highly correlated with academic achievement (r = .60). A stepwise regression analysis revealed that relationship with mother, academic achievement, and alcohol use accounted for 56% of the total variance in academic expectations. Stepwise regression on academic achievement revealed that cocaine use, marijuana use, and academic expectations accounted for 48% of the total variance.     

A Danish version of the Sensation Seeking Scale and its relation to a broad spectrum of behavioral and psychological characteristics

The primary purpose of the present study was to evaluate the internal consistency and construct validity of the Danish translation of Zuckerman's Sensation Seeking Scale (SSS). The secondary aim was to extend the range of psychological variables and behaviors that have been related to sensation seeking. The sample consisted of 691 subjects (363 males and 328 females) with a mean age of 31.7 years. The internal consistency of the scales was evaluated by coefficient alpha and intercorrelations among the five scales derived from the SSS were computed. Information on other variables was collected through standardized tests as well as questionnaires and interviews developed especially for this study. The results showed that the Danish SSS is a psychometrically sound instrument and revealed the relationship between sensation seeking and a broad spectrum of psychological traits and behaviors: socioeconomic status, academic achievement, intelligence, personality, smoking, alcohol and drug use, sexuality, driving and public transportation violations, and leisure time activities. Thus, this study confirmed and expanded the findings of many previous studies, while the results supported the validity of the Danish SSS and corroborated the usefulness of the concept of sensation seeking.