Transcortical sensory aphasia: Evidence for subtypes

Impaired auditory comprehension and fluent but semantically empty speech in conjunction with preserved repetition characterize the syndrome of transcortical sensory aphasia (TSA). Repetition, however, may be mediated by at least two distinct processes--a lexical process that may involve the recognition and subsequent activation of discrete stored word representations and a nonlexical process that involves phonologic decoding and immediate phonologic encoding from immediate memory. We investigated the spontaneous speech, reading, and tendency to recognize and spontaneously correct syntactic errors in four patients with TSA: this analysis suggests there are two subtypes of TSA. We contend that in one subtype both the lexical and direct repetition (or speech production) mechanisms are preserved, but in the second subtype the lexical mechanism is disrupted and repetition is mediated by the nonlexical mechanism.     

Read but not write “Idea”: Evidence for a third reading mechanism

Most information processing accounts of reading incorporate either two or three mechanisms by which oral reading may be accomplished. The existence of a “third” mechanism by which words may be read lexically but without semantic mediation remains controversial. We report data from a patient (W.T.) with an infarction involving Wernicke's area who was unable to write, repeat, or comprehend words of low imageability yet read these and other words reliably; the patient could not, however, read nonwords. As the patient was unable to read on the basis of sublexical print-to-sound correspondences and, at least for words of low imageability, was unable to read by means of a semantically mediated process, the data from this patient are most readily accommodated by models of reading incorporating three mechanisms.     

Effects of variable-interval value and amount of training on stimulus generalization.

In Experiment 1 pigeons pecked a key that was illuminated with a 501-nm light and obtained food by doing so according to a variable-interval (VI) schedule of reinforcement, the mean value of which differed across groups: either 30 s, 120 s, or 240 s. The pigeons in all three groups were trained for 10 50-min sessions. Generalization testing was conducted in extinction with different wavelengths of light. Absolute and relative generalization gradients were similar in shape for the three groups. Experiment 2 was a systematic replication of Experiment 1 using line orientation as the stimulus dimension and a mean VI value of either 30 s or 240 s. Again, gradients of generalization were similar for the two groups. In Experiment 3 pigeons pecked a key that was illuminated with a 501-nm light and obtained food reinforcers according to either a VI 30-s or a 240-s schedule. Training continued until response rates stabilized (> 30 sessions). For subjects trained with the 30-s schedule, generalization gradients were virtually identical regardless of whether training was for 10 sessions (Experiment 1) or until response rates stabilized. For subjects trained with the VI 240-s schedule, absolute generalization gradients for subjects trained to stability were displaced upward relative to gradients for subjects trained for only 10 sessions (Experiment 1), and relative generalization gradients were slightly flatter. These results indicate that the shape of a generalization gradient does not necessarily depend on the rate of reinforcement during 10-session single-stimulus training but that the effects of prolonged training on stimulus generalization may be schedule dependent.     

Review of William Paley, <Emphasis Type="Italic">Natural Theology</Emphasis>, edited with an introduction and notes by Matthew D. Eddy and David Knight

Matthew D. Eddy and David Knight’s new edition of William Paley’s Natural Theology deserves to become the standard scholarly edition of what is a historically, theologically, and philosophically important work, despite a certain neglect of philosophical issues on the part of the editors.     

Social information processing and job characteristics.

This study simultaneously tested 2 theories that attempt to explain differences in job satisfaction: job characteristics theory (Hackman & Oldham, 1976) and social information processing theory (Salancik & Pfeffer, 1978). The theories were tested using data collected from the civilian employees of the public works division at a U.S. military base. The results indicated that individuals' social environments had significant effects upon their attitudes. Multiple social networks were used to operationalize individuals' social environments. The results also suggested that job characteristics had an independent main effect upon job satisfaction, in addition to the effects of the social environment. Based on prior research, employees' past experience and self‐monitoring were tested as moderators of the effects of the social environment, and growth need strength was tested as a moderator of the effects of job characteristics upon job satisfaction. Only self‐monitoring was found to have a significant moderating effect on the relationship between information from the social environment and job satisfaction, and growth need strength had no significant moderating effect.     

Increased spreading activation in depression

The dopaminergic system is implicated in depressive disorders and research has also shown that dopamine constricts lexical/semantic networks by reducing spreading activation. Hence, depression, which is linked to reductions of dopamine, may be associated with increased spreading activation. However, research has generally found no effects of depression on spreading activation, using semantic priming paradigms. We used a different paradigm to investigate the relationship between depression and spreading activation, one based on word frequencies. Our sample included 97 undergraduates who completed the BDI-II and the Controlled Oral Word Association test as well as the Animal Naming test. The results indicated that the group scoring within the depressed ranged evidenced greater spreading activation as compared to those who scored within the normal range on the BDI-II. The implications of these results as they relate to creativity in depression is discussed.     

Responding of pigeons under variable-interval schedules of signaled-delayed reinforcement: effects of delay-signal duration.

Two experiments with pigeons examined the relation of the duration of a signal for delay ("delay signal") to rates of key pecking. The first employed a multiple schedule comprised of two components with equal variable-interval 60-s schedules of 27-s delayed food reinforcement. In one component, a short (0.5-s) delay signal, presented immediately following the key peck that began the delay, was increased in duration across phases; in the second component the delay signal initially was equal to the length of the programmed delay (27 s) and was decreased across phases. Response rates prior to delays were an increasing function of delay-signal duration. As the delay signal was decreased in duration, response rates were generally higher than those obtained under identical delay-signal durations as the signal was increased in duration. In Experiment 2 a single variable-interval 60-s schedule of 27-s delayed reinforcement was used. Delay-signal durations were again increased gradually across phases. As in Experiment 1, response rates increased as the delay-signal duration was increased. Following the phase during which the signal lasted the entire delay, shorter delay-signal-duration conditions were introduced abruptly, rather than gradually as in Experiment 1, to determine whether the gradual shortening of the delay signal accounted for the differences observed in response rates under identical delay-signal conditions in Experiment 1. Response rates obtained during the second exposures to the conditions with shorter signals were higher than those observed under identical conditions as the signal duration was increased, as in Experiment 1. In both experiments, rates and patterns of responding during delays varied greatly across subjects and were not systematically related to delay-signal durations. The effects of the delay signal may be related to the signal's role as a discriminative stimulus for adventitiously reinforced intradelay behavior, or the delay signal may have served as a conditioned reinforcer by virtue of the temporal relation between it and presentation of food.