Stimulus-independent thought depends on central executive resources

Stimulus-independent thoughts (SITs) are streams of thoughts and images unrelated to immediate sensory input. Four experiments examined the contribution of aspects of working memory to production of SITs. In Experiments 1 and 2, interventions that were targeted on, respectively, phonological and visuospatial components of working memory both interfered with production of SITs, but there was evidence that these tasks also made demands on central executive resources. Experiments 3 and 4 specifically examined the hypothesis that production of SITs and control of nonproceduralized tasks both depend on central executive resources, and so should show mutual interference. In Experiment 3, prior practice on pursuit rotor and memory tasks reduced the interference with SITs from concurrent task performance. In Experiment 4, randomness within a task involving random-number generation was less when SITs were being produced concurrently than it was when they were not. The results suggest that production of SITs depends on central executive resources.     

GUIDED VISUAL SEARCH IS A LEFT-HEMISPHERE PROCESS IN SPLIT-BRAIN PATIENTS

Abstract— Previous research has shown that split-brain (callosotomy) patients search through visual displays twice as fast as normal observers when items are divided evenly between visual hemifields, as though each disconnected hemisphere possessed its own attentional scanning system (Luck, Hillyard, Mangun, & Gazzaniga, 1989, 1994) Results from 3 split-brain patients in the present study indicate that the ability to limit search to a relevant subset of the visual display is lateralized to the left cerebral hemisphere. This ability to perform guided search was not shown in the right hemisphere, even when the search time in that hemisphere was superior to search time in the left Furthermore, guided search was observed for both hemifields in normal control observers. These findings suggest that, as with higher cognitive processes such as language, strategic visuospatial attentional processes are preferentially lateralized to the left cerebral hemisphere. The findings also imply that the callosum mediates guided search in the right hemisphere of normal subjects     

Case study: Examining the relationship between self-initiations of an individual with disabilities and directive behavior of staff persons in a residential setting

This case study examines the relationship between self-initiations of an adult woman with severe disabilities and the directive behavior of staff persons in a community residential setting. Hypotheses generated from functional assessment procedures indicated that (a) Susan's low self-initiations were very likely related to high directive behavior of staff persons, and (b) infrequent problem behaviors during the morning routine were maintained by escape from repeated staff demands. An intervention was implemented to enable Susan to increase self-initiation in choice and sequence of activities and simultaneously decrease staff directives. Results and discussion focus on the need for a contextual approach for addressing problematic situations and an affirmation of the effectiveness of the positive behavioral support technology for increasing adaptive behaviors in individuals with severe disabilities.     

Functional Aspects of Recollective Experience in Face Recognition

This article describes two experiments on awareness in recognition memory for novel faces. Two kinds of awareness, recollective experience and feelings of familiarity in the absence of recollective experience, were measured by "remember" and "know" responses. Experiment 1 showed that "remember" but not "know" responses were reduced by divided attention at study. Experiment 2 showed that massed versus spaced repetition of faces in the study list had the opposite effects on "remember" and "know" responses. Massed repetition increased "know" responses and reduced "remember" responses. Spaced repetition increased "remember" responses and reduced "know" responses. The results of both experiments replicate previous findings from the verbal domain in the domain of face recognition, and hence they increase the ecological validity of this experiential approach to memory and awareness and the generality of its database. These findings are discussed from a rehearsal perspective on factors influencing the two states of awareness and in relation to the alternative "process dissociation" procedure.     

Are microsaccades responsible for the gap effect?

Extinguishing a fixation point shortly before, or concurrently with, the onset of a peripheral visual target reduces the latency of saccades to that target. Saslow (1967) hypothesized that thisgap effect might occur because fixation point offsets reduce the incidence of corrective microsaccades with an associated saccadic refractory period. In the present study, a robust gap effect was obtained. However, using a Purkinje image eyetracker with 1 arcmin of resolution, we found that fixation point offsets had no effect on the occurrence of microsaccades and that the occurrence of microsaccades had no impact on the magnitude of the gap effect. Microsaccades therefore do not appear to play any part in the production of the gap effect.     

Effects of surface texture on weight perception when lifting objects with a precision grip

In this paper, we show that, when lifting an object using a precision grip with the distal pads of the thumb and index finger at its sides, the perceived weight depends on the object’s surface texture. The smoother the surface texture, the greater the perceived weight. We suggest that a smoother object is judged to be heavier because the grip force, normal to the surface, required to prevent it from slipping is greater. The possibility of there being an influence of surface texture per se is excluded by a second experiment that employed a variant of the precision grip in which the thumb supports the weight of the object from underneath. With the grip oriented in this way, there is no need to match grip force to surface texture and, under these conditions, there is no effect of surface texture on weight perception. In the first two experiments, the test and comparison weights were lifted successively by the same hand. In a third experiment, the effect of surface texture was replicated for sequential lifts made with separate hands. Thus, the effect is not restricted to comparisons made with the same hand.     

Audit and family systems consultation: evaluation of practice at a child and family centre

This audit of practice at a child and family centre included a 16-month case note review covering 319 cases, a postal survey of 45 families and an interview survey of ten GPs who typically referred cases to the centre. The audit furnished information from three different perspectives on the referral process, the consultation process, and outcome for clients attending the centre. The referral rate was about one new case per day and peak referral times were the beginning of the autumn and winter school terms. Almost half the referrals came from GPs; the remainder were largely from Paediatrics, Education and Social Services. Most clients were seen within two months. Half of the families referred had serious psychosocial difficulties including multiple problem members, multi-problem children, multi-agency involvement, psycho-educational difficulties, child protection problems or child placement difficulties. The majority of cases received six hours of consultation. Families where child abuse had occurred or families containing a multi-problem adolescent received a more intensive service. Between a half and three-quarters of cases had positive outcomes as rated by staff and parents. The service was viewed by GPs to be highly satisfactory. On the negative side, many parents felt ill-prepared for the consultation process and most children did not enjoy the experience.     

Hiding valuables: A questionnaire study of mnemonically risky behavior

A survey investigated incidences where individuals intentionally hid objects but later forgot the item's location. Surveys from 111 younger and 99 older adults yielded the following prototypical scenario: the person hid the valuable 1 year ago to prevent theft, and waited 1 month before an initial 30-minute search, which included looking in dresser drawers plus 1.5 other locations. The person made three additional searches (total searches = 4) for the missing valuable over a 2 week period. Three-quarters of the hidden valuables were eventually found (usually by accident) about 1 month after hiding the object. About half of the time, the person had already searched the hiding area. Older adults typically hid jewellery from thieves, while younger adults hid money from friends and relatives. Older adults searched more often for longer periods of time for the hidden object, and took longer to eventually find the object, compared with younger adults.