The current research was designed to study knowledge development while minimizing methodological problems common to research in that area. First, a procedural network methodology compatible with one commonly used to study declarative knowledge was developed in Experiment 1. In Experiment 2, multiple longitudinal knowledge measures revealed dissociations among the developmental courses of different forms of knowledge. The findings contribute to a growing pool of evidence of the dissociation of declarative and procedural knowledge development. Further, they contradict the majority of knowledge development theories which hypothesize that procedural knowledge development is dependent on the development of declarative knowledge. These findings also indicate that much work needs to be done to determine the relationships among multiple forms of knowledge and to determine how they could be optimally trained. In order for research in these areas to progress, efforts to minimize methodological confounding problems must continue.

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Eighteen right-handed subjects (Ss) between 19 and 33 years of age participated in this EEG study of hemispheric specialization. Ss performed a battery of tasks in three phases which required a range of cognitive activity. The Phase I task involved passive reception of multiple presentations of four auditory stimuli (a pure tone, the vowel /a/, the stop consonant /b/, and a frequency and amplitude modulated tone sweep). Signal averaging was used to derive average evoked responses (AERs) to 28 presentations of each Phase I stimulus at four electrode locations (F(,3), F(,4); P(,3), P(,4); reference: linked ears). In Phase II, Ss performed two auditory attention tasks. In one task the stimuli were six different tones; in the other, they were the six stop consonant speech sounds. In both tasks Ss were instructed to attend to the stimuli and compare the sound following the appearance of a signal light to the one which preceded it and indicate by pressing a hand-held microswitch whether the sounds were the same or different. Five comparison trials were presented during each task; no EEG analysis was performed during the comparison trials. AERs to 34 stimulus presentations in each task were derived at the four electrode sites. In addition, frequency aspects of the EEG during Phase II tasks were examined by computing power spectra. All stimuli in Phases I and II were generated by computer, were randomly ordered, 300 milliseconds in duration, with an interstimulus interval randomized between 2, 3, and 4 seconds. Phase III was the most cognitively demanding Phase wherein Ss performed verbal, baseline, and spatial tasks. The verbal and spatial tasks were performed twice with an alternate form of each task used for the repetition. The baseline task was performed prior to each cognitive task. Items for the verbal task were nouns of low imagery and concreteness value while the spatial task involved mental rotation of geometric shapes. The baseline task elicited sensory and motor activity similar to that required by the verbal and spatial tasks, but did not require problem solving. Power spectra were computed during each of the Phase III tasks. Measures of the AER and power spectra data from the three phases were statistically analyzed one at a time using univariate analysis of variance with an Epsilon correction. These analyses showed many task and lead main effects in all three phases of the study, indicating that the Ss did have different EEG responses to the various stimuli and tasks. In Phase III there was a task by lead interaction in the alpha band (8-13 Hz) analysis of parietal activity in which the right parietal power was greater than the left parietal power during the verbal task. There was a difference in the same direction and of the same magnitude during the baseline task. During the spatial task the relative difference between right and left parietal leads was at its maximum, but its direction was counter to the view of the relation between the EEG and hemispheric specialization wherein one would predict relative alpha suppression in the right hemisphere during the performance of a spatial task. The results of this experiment are not consistent with the notion that the EEG reflects hemispheric specialization.

An interactive method for structural analysis of the subjective organization of human memory is developed which is based upon analysis of interitem proximities derived from free recall interresponse times. The proximity analysis is shown to be effective in revealing organizational structure through the use of both cluster and multidimensional scaling analyses. This technique is tested in a series of multitrial free recall experiments in which the presentation order of stimuli on trial N + 1 is determined by a real-time cluster analysis of recall data from the previous N trials. In the Clustered condition, items on the second and subsequent trials are presented blocked by clusters. This condition is contrasted with Random, Yoked and Fixed presentation orders, using both strongly and weakly categorizable lists. The Yoked group learned faster than the Random group with categorized lists and not as fast with uncategorized lists, indicating that the clustering had some effect upon developing organizational structure. Surprisingly, the Clustered group learned only slightly faster than the Yoked and Random groups, and not as fast as the Fixed group with both types of lists. These results are explained in terms of the qualitative nature of the information provided to the learner in each of the experimental conditions. This structural analysis approach to the measurement of memory organization is recommended for future research in semantic memory.

A series of experiments was conducted to elucidate the role(s) of special or strategic effortful processes in the encoding and retrieval of frequentistic information. Previously, investigators have concluded that sensitivity to frequency was the result of an "automatic" mechanism. However, it is difficult to generalize these findings to what people do when processing real-world frequentistic data because most studies have involved highly artificial experimental stimuli. By contrast, the present series of studies employed multidimensional stimuli that had real world significance to the participants. The complexity and realism of the stimuli facilitated the relatively unobscured assessment of the cognitive processes involved in frequency encoding. The purpose of Experiment 1 was to classify individuals according to the ability to "timeshare" in a dual-task setting. Timesharing ability was operationalized in terms of subject responsiveness to a payoff scheme which was designed to induce tradeoffs in the distribution of attentive effort between two concurrent tasks. The thrust was on the classification of prospective subjects for further investigations of frequentistic encoding and retrieval operations. A sample of four subjects in possession of uniformly good to excellent timesharing skills was enlisted for participation in the subsequent experiments. In Experiment 2, a complex rating task was used to test the hypothesis that special effortful processing is required in the formation of frequency records. The task involved the consistent aggregation of the evaluative cues comprising hypothetical candidate profiles. The principal question was whether the encoding of frequency information would be an incidental by-product of the effortful processing associated with the rating task. The negative findings strongly suggest that special (or strategic) effortful processing is required in the formation of reasonably accurate frequency records. In Experiment 3, the tasks of frequency estimation and hypothetical candidate rating were examined concurrently in a dual-task paradigm. A pronounced performance tradeoff was found between the two tasks; that is, improved performance on the frequency task was gained at the expense of degraded rating task performance, and vice versa. This suggests that whatever the processes governing frequentistic encoding operations, they draw upon the same pool of limited cognitive resources as those governing the rating task. This, of course, provides further support for the view that frequency encoding is the result of special effortful processing strategies. Implications of these findings for real-world decision making are examined, and ideas for future research are discussed.

Memory inhibition has been the subject of much thought and, in this century, much research. Laboratory findings of inhibition to date, however, have virtually all involved creating an incongruity between the study and test contexts, the conditions under which a memory is formed and those under which it is evinced. Studies reported here demonstrate what can be construed as a qualitatively different type of memory inhibition, one that is in some sense context-free. When a just-studied word is tested for recall with word-fragment cues of successively increasing strength (e.g., R------P; R----R-P; R-I--R-P; R-I--ROP), each presented for 4 seconds, performance is impaired compared to when only the strongest fragment cue (R-I--ROP) is presented for 4 seconds, even though in the first case there is additional opportunity for subjects to recall the word (RAINDROP). Indeed, level of performance varies systematically with initial cue strength. Thus, for example, if cuing starts with a 3-letter fragment, the word is recalled less often than if it starts with a 4-letter fragment but more often than if it starts with a 2-letter fragment. Moreover, the effect remains essentially undiminished even if subjects are allowed an additional full minute with the critical cue (R-I--ROP). Since the procedure used here involves manipulating only the graphemic aspects of a given word and not the context in which it was learned, the inhibition is context-free. The inhibition is discussed in light of a theoretical distinction (Mandler, 1980) between elaboration and integration processes in list learning. Another finding of interest is that no such inhibitory effect occurs when the to-be-discovered words are not studied before the test. When subjects try to complete the word fragments on the basis of their general knowledge of words, or "semantic memory," performance between the successive and single-level cuing conditions does not differ. The overall pattern of results therefore provides strong support for the episodic-semantic memory distinction formulated by Tulving (1972).