Long-term memory in pigeons: I. The role of discrimination problem difficulty assessed by reacquisition measures II. The role of stimulus modality assessed by generalization slope

Pigeons learned either an easy or a difficult line angle discrimination (Experiment 1) or wavelength discrimination (Experiment 2), and then they were given a reacquisition test of retention after delays of 1 min, 1 day, or 1 week. Both percentage of responses to the S+ in the initial 10-trial block and number of blocks to criterion showed a progressive memory loss which was greater for the difficult problem. These results extend recent findings by using a free operant rather than a discrete trial task and by varying problem difficulty by altering the dimensional separation between training stimuli. In Experiment 3, pigeons were given variable interval training with either a wavelength or a line angle stimulus, and then they were tested for generalization in extinction after delays of 1 min, 1 day, and 1 week. With both dimensions, the relative gradients became progressively flatter with increasing delay intervals. This replicates earlier findings and extends them to the line angle dimension. The evidence of substantial forgetting in the first 24 h in all three experiments suggests that operant free-response procedures are more sensitive to forgetting effects than are discrete trial tasks.     

Asymmetrical effects of Pavlovian excitatory and inhibitory aversive transfer on Pavlovian appetitive responding and acquisition

Predictions of a theory of Pavlovian motivational transfer, which incorporates principles of both the theory of reciprocal inhibition and the Rescorla-Wagner model, were tested in several Pavlovian aversive to Pavlovian appetitive transfer tasks. As predicted, the presence of a signal for an aversive event, conditioned stimulus (AV CS+), reliably suppressed performance of appetitive conditioned responses (CRs) whether imposed during acquisition or on independently established responding. Acquisition of appetitive responding to a novel CS reinforced in compound with an AV CS+, however, was enhanced (“superconditioning”). This observation suggests that the effects of a discrepancy between expectation and actual outcome on a conditioning trial are influenced by the affective value of both the expectation and the reinforcer. These transfer effects were not symmetrical for an inhibitory aversive stimulus (AV CS?). An AV CS? did not enhance appetitive responding compared to a random control condition, nor did the AV CS? reduce (i.e., block) appetitive conditioning to a novel CS when appetitive reinforcement occurred in the presence of the AV CS?. Comparison of the two shock-exposed conditions with a naive control condition suggests that previous results that were apparently consistent with inhibitory aversive enhancement and blocking of appetitive conditioning may have been due to aversive context conditioning.     

Development of phonetic memory in disabled and normal readers

The development of phonetic codes in memory of 141 pairs of normal and disabled readers from 7.8 to 16.8 years of age was tested with a task adapted from L. S. Mark, D. Shankweiler, I. Y. Liberman, and C. A. Fowler (Memory & Cognition, 1977, 5, 623–629) that measured false-positive errors in recognition memory for foil words which rhymed with words in the memory list versus foil words that did not rhyme. Our younger subjects replicated Mark et al., showing a larger difference between rhyming and nonrhyming false-positive errors for the normal readers. The older disabled readers' phonetic effect was comparable to that of the younger normal readers, suggesting a developmental lag in their use of phonetic coding in memory. Surprisingly, the normal readers' phonetic effect declined with age in the recognition task, but they maintained a significant advantage across age in the auditory WISC-R digit span recall test, and a test of phonological nonword decoding. The normals' decline with age in rhyming confusion may be due to an increase in the precision of their phonetic codes.     

A process model for water jug problems

We develop and evaluate a model for the water jug task in which a subject is required to find a sequence of moves (pouring operations) which produce a specified amount of water in each jug. Experiment 1 was designed to evaluate the meansends, move selection heuristics that are assumed by the model. Experiment 2 tested the model's predictions concerning those aspects of the water jug task that determine problem difficulty.A three stage process model incorporating GPS-like, means-ends heuristics and assumptions concerning the utilization of short- and long-term memory was able to account for differences across problems as well as details of the performance of subjects solving a given problem. We conclude that a GPS-like model that only selects one move at a time (no forward planning of move sequences or setting up of subgoals) can provide a good account of solution behavior in the water jug task.     

Time sharing and dichotic listening asymmetry in normal and learning-disabled children

Time-sharing and dichotic listening techniques were used to examine cerebral lateralization for language function in 48 normal and 48 learning-disabled children. All subjects were matched according to age, sex, and handedness. An analysis of results indicated that both nornal and learning-disabled children demonstrated left hemisphere lateralization of language function on the time-sharing and dichotic listening tasks. However, no developmental trends were evident for either group. Differences observed in the performance of the normal and learning-disabled children may relate to how each group utilizes “verbal strategies” and processes simultaneous information in the left hemisphere. The results strongly question the notion that attributes learning disabilities to incomplete or delayed language lateralization and lend support to the notion that cerebral lateralization is not a developmental phenomena.     

Interactive processes in sentence comprehension and recognition

Two experiments examined the roles played by semantic and surface information in reading and recognizing sentences. Subjects read sentences in normal and inverted typography. Their recognition of meaning and other sentence features was tested using sentences whose typography, wording, and/or meaning were either the same as or different from that in the first set of sentences. In Experiment 1, subjects either read aloud or performed a sentence continuation task. For originally inverted sentences, recognition of meaning was high, irrespective of task demands. For originally normal sentences, recognition was low for Read Aloud subjects and high for Sentence Continuation subjects. Sentence recognition was affected by repetition of wording and typography. Experiment 2 replicated the results with the read aloud task and showed the second reading of originally inverted sentences to be equally swift for paraphrase and verbatim test forms. It was concluded that reading and recognition are interactive processes, involving conceptually driven and data driven operations. The interaction of operations may be either automatic or controlled. While processing of normal typography is automatic, inverted typography induces controlled processing, resulting in better retention. Furthermore, semantic and surface information are conceptualized as interacting components of comprehension and memory processes.     

Exposure to inescapable shock produces both activity and associative deficits in the rat

Interference with shuttle-box escape learning following exposure to inescapable shock is often difficult to obtain in rats. The first experiment investigated the role of shock intensity during escape training in the apparent fragility of the effect. Experiment 1A demonstrated that the magnitude of the interference effect was systematically related to shock intensity during shuttle-box testing. At .6 mA, a robust effect was obtained, whereas at .8 mA and 1.0, little or no deficit in the escape performance of inescapably shocked rats was observed. Experiment 1B demonstrated that the deficit observed in Experiment 1A depended upon whether or not rats could control shock offset. Experiment 2 suggested that preshock may suppress activity and that higher shock levels may overcome this deficit. Experiment 3 tested this as the sole cause of the escape deficit by requiring an escape response which exceeded the level of activity readily elicited by a 1.0-mA shock in both restrained and preshocked rats. In such a task, preshocked rats performed more poorly than did restrained controls. These results are consistent with the possibility that inescapable shock may, in addition to reducing activity, produce an associative deficit. Experiment 4 more clearly demonstrated that inescapable shock produces deficits in performance which cannot be expleined by activity deficits and which appear to be associative in nature. It was shown that inescapable shock interfered with the acquisition of signaled punishment suppression but not CER suppression. The theoretical implications of these data for explanations of the manner in which prior exposure to inescapable shock interferes with escape learning were discussed.     

Therapy and immunization of long-term analgesia in rats

Three experiments are reported which examine the effects of experience with escapable shock either subsequent to (Experiment 1) or prior to (Experiments 2 and 3) a session of inescapable shock on the subsequently produced long-term analgesic reaction in rats. Experment 1 demonstrated that experience with escapable shock 4 hr after a session of inescapable tail shock completely reverses the analgesic response that is normally observed 24 hr later upon reexposure to shock. The escapability of the shock was shown to be the important factor in reversing the analgesic reaction, since subjects given inescapable shock in amounts equivalent to escape subjects exhibited no reduction in analgesia. Experiment 2 showed that experience with escapable shock 4 hr prior to a session of inescapable tail shock could also completely eliminate the long-term analgesic reaction. Experiment 3 replicated the results of Experiment 2, but employed a different escape task and temporal parameters in order to extend the generality of the findings, and to more closely match the procedures employed in behavioral experiments reported by J. L. Williams and S. F. Maier (Journal of Experimental Psychology: Animal Behavior Processes, 1977, 3, 240–253). The implications of these results for the areas of pain control and learned helplessness were discussed.