The role of inhibition in a spreading-activation model of language production. II. The simulational perspective

This is the second part of a project aimed at establishing the role of lateral inhibition in spreading-activation models of language production. While the first part (Berg &; Schade, 1992) reviewed the psycholinguistic evidence for inhibition and established that indeed inhibition takes place, this paper addresses the issue from the implementational perspective. A series of computer simulations are reported in which spreading-activation models with or without inhibition are directly contrasted. The performance of the competing models is evaluated against two sets of criteria. On the more technical side, the “heat death” and the selection problems have to be solved. That is, the target must have a high and the nontarget units a low level of activation. Additionally, there are certain empirical effects from the production literature which may serve as test cases for deciding between the rival models. The results of the simulations indicate that only the inhibition-based model proves capable of meeting all challenges. All inhibitionless variants fail in one or more respects. It is further shown that the need for the inhibitory component increases with the size of the processing network and that one well-known production model can do without lateral inhibition only at the expense of introducing a concept which resembles inhibition in its effect but cannot replace it.     

Single and combined effects of methylphenidate and behavior therapy on the classroom performance of children with attention-deficit hyperactivity disorder

Twenty-four boys with attention deficit-hyperactivity disorder (ADHD) participating in an intensive summer treatment program each received b.i.d. placebo and two doses of methylphenidate (MPH, 0.3 mg/kg and 0.6 mg/kg) crossed with two classroom settings: a behavior modification classroom including a token economy system, time out and daily home report card, and a regular classroom setting not using these procedures. Dependent variables included classroom observations of on-task and disruptive behavior, academic work completion and accuracy, and daily self-ratings of performance. Both MPH and behavior modification alone significantly improved children's classroom behavior, but only MPH improved children's academic productivity and accuracy. Singly, behavior therapy and 0.3 mg/kg PMH produced roughly equivalent improvements in classroom behavior. Further, the combination of behavior therapy and 0.3 mg/kg MPH resulted in maximal behavioral improvements, which were nearly identical to those obtained with 0.6 mg/kg MPH alone.The authors gratefully acknowledge the assistance of Patricia Donovan, Michelle Berry, Mary Ingram, Patricia Wells, Beth Gnagy, Karen Greenslade, Mary Hamilton, and the entire staff of the Western Psychiatric Institute and Clinic ADHD Summer Treatment Program.     

Computer-Assisted Careers Guidance Systems and Organisational Change

This article describes a study conducted to identify the range of potential influences that a computer-assisted careers guidance system (PROSPECT (HE)) had on the functioning of organisations (careers services in higher education). Data from six institutions indicated that use of PROSPECT (HE) was associated with important and varied change within the organisations. It appears that when a careers service seeks opportunities for change, CACG systems can be an important catalyst for change in two respects: by providing a focal point for achieving previously established goals; or, as a consequence of system use, by making staff aware of the potential for new organisational goals.     

The tunnel effect,Gibson's perception theory,and reflective seeing

Summary Subjects can have continuous visual experience of an object's movement across a display though the movement's middle phase takes place behind an opaque screen. The present article considers explanatory issues pertaining to this so-called, tunnel effect, with special reference to Gibson' s perception theory and the visual activity that I have been calling reflective seeing. Among the issues discussed are the following. (a) In the tunnel experiments, I suggest, there occur both persisting perception, as Michotte held, and persistence perception, as Gibson held. The subjects pick up stimulus information that allows visually experiencing the object's going out of sight at one edge of the screen and coming back into sight at another edge of the screen; the subjects have visual experience of the continued existence and movement of the object while it is out of sight. Moreover, persistence of perceptual experience is involved: when the object goes out of sight, the subjects' visual experience of its movement goes on. (b) I also argue that the tunnel effect is a phenomenon of both straightforward and reflective seeing. Adopting a phenomenal attitude, as one does when reporting one's perceptual experience, one still sees movement taking place on the other side of the screen, as one does in straightforward seeing. However, whereas straightforward seeing does not give inner awareness of visual experience, the subjects in the tunnel experiments report visually experiencing the object's movement while also visually experiencing the opaque screen in front of it as opaque. I argue that these reports, and those about the object's going out of and coming back into sight, must be based on the kind of visual experience that is part and product of reflective seeing.     

A PRESCRIPTION FOR GENERATING A NEW PARADIGM IN THE CONTEXT OF SCIENCE AND THEOLOGY

Abstract. Many centers are now active in the study of the interaction between science on the one hand and theology on the other. Suggestions are made as to how such study might be furthered. The central proposal in this paper is based on the author's experience in founding and, over many years, operating the Neurosciences Research Program (NRP). The "faculty" of this group were highly competent in many fields of science and were able to deal with many of the major issues. It is here further suggested that if an NRP-like organization were established, capable of productively interacting with both science and theology, it might well generate new concepts and possibly a new paradigm in this context.     

Family reunions: Visionary encounters with the departed in a modern-day psychomanteum

A poignant feature of many near-death experiences is a visionary encounter with deceased loved ones. Over the centuries, researchers have sought safe ways to replicate near-death and related experiences, hoping to induce the powerful aftereffects of these events. The ancient Greeks contructed psychomanteums, or oracles of the dead, where seekers could consult spirits of the deceased. I describe a modern attempt to recreate the psychomanteum. Like near-death experiences, visionary encounters in this modern psychomanteum are experienced as real and not as hallucinatory, and have profound personal aftereffects. This novel experimental technique may permit the scientific study of phenomena that previously occurred only spontaneously and under uncontrolled circumstances.     

Neighborhood frequency effects and letter visibility in visual word recognition

Two experiments are described that measured lexical decision latencies and errors to five-letter French words with a single higher frequency orthographic neighbor and control words with no higher frequency neighbors. The higher frequency neighbor differed from the stimulus word by either the second letter (e.g.,astre-autre) or the fourth letter (chope-chose). Neighborhood frequency effects were found to interact with this factor, and significant interference was observed only tochope-type words. The effects of neighborhood frequency were also found to interact with the position of initial fixation in the stimulus word (either the second letter or the fourth letter). Interference was greatly reduced when the initial fixation was on the critical disambiguating letter (i.e., the letterp inchope). Moreover, word recognition was improved when subjects initially fixated the second letter relative to when they initially fixated the fourth letter of a five-letter word, but this second-letter advantage practically disappeared when the stimulus differed from a more frequent word by its fourth letter. The results are interpreted in terms of the interaction between visual and lexical factors in visual word recognition.