Feature-specific interference in letter identification

It is a well documented finding that letter identification may be impaired by the presence of neighboring characters. There is much less agreement about the exact nature of such lateral interference. Evidence has been obtained for feature-specific interference, and even feature-specific facilitation. Santee and Egeth (1980) suggested that feature-specific interference will mainly be observed in data-limited situations where stimuli are presented for short durations and positional uncertainty is involved. They further suggested that interference would be revealed in accuracy rather than latency measures.In our first experiment, similar exposure conditions were used to those suggested by Santee and Egeth. In a second experiment, however, a longer exposure duration was used, and latency measurements were also collected. In a third experiment, positional uncertainty was removed by foveal presentation, and with this high quality stimulus presentation only latency measurements could be obtained.In all these experiments clear evidence for feature-specific interference was found, both in accuracy and latency data, and these results also held up under the detectability/criterion analysis proposed by Estes (1982). From these findings it can be concluded that feature-specific interference occurs under a wide range of conditions, including those representative of normal reading.     

Preprogramming vs. on-line control in simple movement sequences

In the present experiment the acceleration traces produced during a repetitive arm extension/flexion movement were measured in addition to the RT required to initiate such a movement. The speed at which this task was completed as well as the number of extension/flexion segments were varied to allow for either preprogramming or on-line control. Evidence from the acceleration traces and the RT data suggested that the movements completed as quickly as possible were preprogrammed; whereas, those completed more slowly were controlled on-line. Furthermore, the topologies of the power spectral density functions from the acceleration traces of each type of movement displayed characteristics typical of these forms of control.     

Group psychotherapy in chronic psychiatric outpatients: a Toronto model.

Seventy to 80 chronic psychiatric patients are treated in an aftercare clinic with a goal of tertiary preventive care. The major component of the treatment approach is reality-oriented group psychotherapy with an emphasis on interpersonal relationships. Attention to three factors in group psychotherapy with this population of patients has facilitated our work and outcome. These are the concept of the core group, diagnostic heterogeneity, and staff structure.     

Work-Home Role Conflict,Family Climate,and Domestic Responsibilities Among Men and Women in Dual-earner Families1

Correlates of work-home role conflict for dual-earner couples were examined. Respondents (N= 208) were an equal number of married, employed men and women with children. Data were collected in the northeastern U.S.A. through a survey which measured work-home role conflict, family climate, domestic responsibilities, and activities performed during one's free time. LISREL was used to determine if domestic responsibilities mediate the correlation between gender and work-home conflict. A regression analysis was used to determine the relative effects of domestic responsibilities and family climate on work-home conflict. Results indicate that (a) work-home role conflict is negatively related to family climate for men as well as for women, (b) gender differences in role conflict are partially attributable to gender differences in domestic responsibilities, and (c) domestic responsibilities and family climate each correlate significantly with work-home role conflict. Findings suggest that how one works hard (the conditions under which one lives) may be just as important as how hard one works (the number of tasks one performs).     

INDUCING VARIABILITY IN COMMUNICATIVE GESTURES USED BY SEVERELY RETARDED INDIVIDUALS

Handicapped individuals who have been taught spontaneous gesture requests often use only a small part of their vocabulary. Procedures to recover the unused part of this vocabulary have not been documented. This study was designed to identify procedures for increasing the proportion of gestures used spontaneously. Six mentally handicapped individuals served as subjects. After a baseline phase during which spontaneous gesture requests were reinforced, consequences were withheld for high-rate gesture requests. This led to an increase in different gesture requests. Although gesture requests did not return to baseline levels during a reversal condition, functional control was demonstrated by way of a multiple baseline across subjects. The absence of a reversal effect suggests enduring effects of the procedure.     

Local and global mechanisms of one- and two-dimensional orientation illusions.

One-dimensional (1-D) orientation illusions induced on a test grating by a tilted and surrounding 1-D inducing grating have a well-known angular function that exhibits both repulsion and attraction effects. Two-dimensional (2-D) orientation illusions are those induced on a test grating by 2-D image modulation, such as a pair of superimposed inducing gratings at different orientations, usually orthogonal (a plaid). Given the known angular functions induced by the plaid component gratings, two hypotheses were developed that predicted different plaid-induced illusion functions. Hypothesis 1 states that the 1-D component-induced effects simply add linearly; Hypothesis 2 states that there is an additional mechanism that responds to the virtual axes of mirror symmetry of the plaid and adds to the effect. The data of two experiments were consistent with the predictions from the second hypothesis but not the first. Possible neural substrates of mechanisms that extract axes of symmetry are discussed; it is suggested that such global symmetry axes may underlie the perceived orientation of complex shapes.     

The enhancement of retention induced by vasopressin in mice may be mediated by an activation of central nicotinic cholinergic mechanisms.

Immediate post-training subcutaneous administration of lysine vasopressin (LVP, 0.003-1.00 microgram/kg) enhanced retention, whereas the vasopressin antagonist AAVP (0.01-0.30 microgram/kg) impaired it, in male Swiss mice tested 48 h after training in an inhibitory avoidance task. Both effects were dose-dependent. Neither LVP nor AAVP affected response latencies in mice not given the footshock on the training trial. The simultaneous administration of AAVP at a dose (0.01 microgram/kg) which had no effect on retention shifted the dose-response curve of LVP to the right. Nicotine (1.0-30.0 micrograms/kg, sc), a central nicotinic cholinergic agonist, also facilitated retention in a dose-related manner without affecting the retention performance of unshocked mice. The effect of nicotine was prevented by the central acting nicotinic cholinergic receptor antagonist mecamylamine (5 mg/kg, sc.). In contrast, neither hexamethonium (5 mg/kg, sc), a peripheral acting nicotinic receptor blocker, nor atropine (0.5 mg/kg, sc) or methylatropine (0.5 mg/kg, sc), two anticholinergic drugs which are known to act on muscarinic cholinergic receptors, prevented the effect of post-training nicotine. The effects of LVP and nicotine were time-dependent, suggesting that both treatments enhanced retention by influencing post-training processes involved in memory storage. Low doses of nicotine (1.50 microgram/kg, sc) or the central anticholinesterase physostigmine (35 micrograms/kg, sc) and LVP (0.003 microgram/kg, sc), which had no effect on retention when administered alone, produced a synergistic interaction when given together following training. The influence of LVP (0.03 microgram/kg, sc) on retention was prevented not only by AAVP (0.01 microgram/kg, sc) but also by mecamylamine (5 mg/kg, sc), whereas the effects of nicotine (10.0 micrograms/kg, sc) were prevented only by mecamylamine. These results suggest that the enhancement of retention induced by vasopressin is probably due to an activation of central nicotinic cholinergic mechanisms which are critical for memory formation.     

A note on partitioned determinants

A formula for the determinant of a partitioned matrix, possibly with singular submatrices, is derived and applied to some psychometric and numerical problems.     

Generalized eigenvalue problems with positive semi-definite matrices

In a recent paper in this journal McDonald, Torii, and Nishisato show that generalized eigenvalue problems in which both matrices are singular can sometimes be solved by reducing them to similar problems of smaller order. In this paper a more extensive analysis of such problems is used to sharpen and clarify the results of McDonald, Torii, and Nishisato. Possible extensions are also indicated. The relevant mathematical literature is reviewed briefly.