Acquisition of representation-mediated conditioned food aversions

Food aversions were established in rats by administering lithium chloride (LiCl) immediately after the presentation of an exteroceptive conditioned stimulus (CS) which previously had been paired with a food substance. In Experiment 1, rats which received first tone-food and then tone-LiCl pairings showed less food consumption in subsequent testing than rats which received only tone-food or tone-LiCl pairings. Experiments 2 and 3 demonstrated the stimulus specificity of aversions established in this manner. Rats which first received pairings of light and tone CSs with two different food substances and then received pairings of one of those CSs with LiCl showed greater aversion to the food previously associated with the LiCl-paired CS than to the other food substance. Experiment 3 also showed that specific aversions were not acquired if rats received CS-shock rather than CS-LiCl pairings. These results suggest that CS-evoked representations of events can substitute for those events themselves in the formation of new associations.     

Categorization and representation of physics problems by experts and novices

The representation of physics problems in relation to the organization of physics knowledge is investigated in experts and novices. Four experiments examine (a) the existence of problem categories as a basis for representation; (b) differences in the categories used by experts and novices; (c) differences in the knowledge associated with the categories; and (d) features in the problems that contribute to problem categorization and representation. Results from sorting tasks and protocols reveal that experts and novices begin their problem representations with specifiably different problem categories, and completion of the representations depends on the knowledge associated with the categories. For, the experts initially abstract physics principles to approach and solve a problem representation, whereas novices base their representation and approaches on the problem's literal features.     

Developmental changes in free recall: The interaction of task structure and age

Free-recall learning and organization were measured for 3rd, 7th, and 11th graders under conditions which varied the type and amount of task structure. Task structure for the input or list-presentation phase was manipulated by using a random, constant, or alphabetic item sequence across trials. Task structure for the output or recall phase was manipulated by providing standard instructions or instructions which suggested the possible use of an alphabetic ordering scheme. Recall performance and organization showed an interaction between age and both manipulations of task structure. The 3rd graders required the maximal amount of task structure (alphabetic order with alphabetic instructions) to demonstrate recall facilitation relative to the completely unstructured control condition. The 7th graders showed recall facilitation for intermediate and high levels of task structure, and the 11th graders showed recall facilitation for low, intermediate, and high levels of task structure. The results are related to current hypotheses about developmental changes in recall performance and their relationship to changes in the systematic use of organizational strategies.     

What the classical aphasia categories can't do for us, and why

A good deal of activity in contemporary aphasia research goes under the label "neurolinguistics." What characterizes this enterprise is, among other things, its goal of identifying neurally realized computational subsystems that support language processing. In this essay the thesis is put forward that this goal will not be served by the continued exploitation of the classical (Wernicke-Lichtheim) taxonomic categories. These categories, it is argued, cannot by virtue of their "polytypic" structure support the relevant neurolinguistic generalizations.     

Transfer of the signaling properties of aversive CSs to an instrumental appetitive discrimination

Rats received Pavlovian conditioning in which, based on a shock US, white noise was established for different groups as an aversive CS+, CSo, or CS?. Then, half of each group received the CS contingent upon either the food-reinforced or nonreinforced response in an easy, choice discrimination. Correct responses, i.e., number of reinforcements, to criterion showed that a CS+ for the reinforced response facilitated learning, whereas a CS? retarded learning; conversely, a CS+ for the nonreinforced response retarded learning, whereas a CS? facilitated learning. The same contingency difference occurred with errors to criterion for CS? subjects but was obscured for CS+ subjects apparently by an avoidance-producing effect of the CS+. In support of the generality of the transfer effect, Z-score transforms of the correct-response data showed that the magnitude of transfer was comparable to that obtained in more difficult discriminations. Collectively, the findings indicate that an aversive CS can function as a transformed signal for the presence (CS+) or absence (CS?) of an appetitive reinforcer and that the signal's control of behavior is via a within-chain mediational process.     

Developmental changes in memory: The effects of processing time and rehearsal instructions

An overt rehearsal procedure was used to investigate the relationship between children's rehearsal strategies and free recall performance. Previous work has shown that developmental differences in rehearsal content, rather than rehearsal frequency, affect recall performance. This experiment investigated the effects of increased processing time and rehearsal training upon recall. Third-grade girls (age 8) were able to use additional processing time to increase the activity of their rehearsal, and they showed corresponding improvement in recall. In contrast, third-grade boys (age 8) and sixth-grade boys and girls (age 12) did not take advantage of a slower presentation rate to rehearse more actively, and their recall did not change. Further, even without additional processing time, both the third-grade boys and girls were able to use an instructed active rehearsal strategy to facilitate their recall. The direct manipulation of rehearsal activity and the resulting improvement in recall provide experimental support for the proposed relationship between rehearsal content and recall from long-term memory store.     

Developmental differences in recall and recognition: The relationship between rehearsal and memory as test expectation changes

An overt rehearsal procedure was used to study the relationship between children's rehearsal strategies and their memory performance under different conditions of test expectation. Previous work has shown that developmental differences in rehearsal content affect recall performance. This study was designed to address the question of why active rehearsal content results in superior recall performance. The equivalence of recognition-memory performance for third- (age 9) and sixthgraders (age 12) suggests that developmental differences in recall are due to the effects of rehearsal content on item retrieval from permanent memory. In addition, the data indicate that third- and sixth-graders can differentiate between expected recall and recognition tests and, with the exception of the sixth-grade boys, use this information to modify their rehearsal content. These differences in rehearsal content, as a function of the type of test expected, corresponded to changes in recall performance.     

Infants and I scales: Inferring change from the ordinal stimulus selections of infants for configural stimuli

The analysis of I-scale preference orders of 71 infants 2 to 9 months old to four face-like stimuli suggested a common J-scale stimulus ordering for each of the four age groups. Changes in I-scale frequencies were used as a measure of age-related changes in preference orders. Results revealed no change in preference for the age period studied. Together with other data these results suggest an ageinvariant preference for organized face-like forms from at least as early as five weeks through 9 months. This finding is at variance with some theoretical expectations. A Thurstone analysis is provided as a contrast to the J-scale analysis. Assumptions of different data analyses are considered as the basis for varying results reported in the literature.     

A test of parallel versus serial processing applied to memory retrieval

Townsend has identified necessary and sufficient conditions that reaction time distributions meet if they are produced by two underlying processes that are parallel and within-stage independent. This paper describes an attempt to use one of these conditions to assess the assumption of independent parallel memory retrieval in Anderson's ACT theory. In the experimental test, subjects studied profession-location pairs, with each profession and location included in two pairs. One pair had a high frequency of presentation and the other had low. When cued with a profession (or location), subjects responded with the first of the two studied locations (or professions) that came to mind. The reaction times to these responses were used to test the ACT assumption of independent parallel search. The problems encountered in trying to apply Townsend's abstract test to a concrete situation included the need to consider mixtures and convolutions of distributions and empirical, rather than theoretical, distributions. These difficulties are discussed at length and some formal analyses concerning their effect on the test are given. Despite these problems, we were able to use Townsend's test and the results of the experiment support the within-stage independent parallel assumption of ACT.