Selective attention: effects of cuing on the processing of different types of compound stimuli

Pigeons in a matching-to-sample experiment received (a) element samples (one of two colors or vertical or horizontal white lines), (b) separated compound samples (a color and a line element presented together), and (c) unified compound samples (vertical or horizontal colored lines). In Phase I, test stimuli were the two elements from one dimension; the dimension tested varied randomly when the sample was a compound. Element samples were matched better than unified samples, which were matched better than separated samples. In Phase II, two samples preceded the tests. On EC trials, the first sample (S1) was an element, and the second sample (S2) was a compound; on CE trials this order was reversed. One element of the compound sample was always the one appearing as the element sample on that trial (e.g., S1 = red, S2 = red-vertical). This element also served as the correct test alternative (e.g., test = red+ vs. green) except on probe trials when the correct test was the other element appearing in the compound (e.g., test = vertical+ vs. horizontal). Accuracy varied as a function of sample sequence when the compound was separated (EC greater than CE on nonprobe trials and CE greater than EC on prove trials). This pattern was not observed when the compound was unified. The data suggest that the element in EC trials served as a cue that increased processing of the cued dimension and decreased processing of the noncued dimension of separated compounds. However, both dimensions of unified compounds seem to have been processed regardless of cuing.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effects of stimuli followed by response-independent shock on shock-avoidance behavior

Four rhesus monkeys were trained on a non-discriminated shock-avoidance schedule (baseline). Stimuli followed by response-independent shock were then presented with the avoidance baseline no longer in effect. The main portion of the experiment consisted of superimposing (independently of responding) the stimuli followed by response-independent shock on the avoidance baseline. Different temporal values of stimulus duration and delay of shock (produced by an avoidance response) were presented successively, using each subject as his own control. When the stimulus duration was short or the delay of shock was long, so that avoidance rate during the stimulus could assume any value without resulting in baseline (avoidable) shocks during the stimulus, a lowered or "suppressed" rate of responding developed during the stimulus. When the stimulus duration was long or the delay of shock was brief, so that avoidable shocks resulted from a response decrement during the stimulus, high or "facilitated" rates of responding developed for a large proportion of the time that the stimulus was present.     

The effects of redundant communications on listeners: Why different types may have different effects

Much of our communication is redundant in that we say more than necessary to be informative. How listeners respond to verbal redundancy is important because of its frequency of occurrence and because such knowledge should enable us to increase our understanding of the development of listening skills. Previous research indicated qualitative developmental differences in how listeners respond to differentiating redundancy (several distinguishing features of a referent are mentioned). The present research compared performance with two forms of redundancy: differentiating and structured (e.g., mentioning a distinguishing referential feature and a feature shared by several contiguous stimuli) and investigated causes of differences in responding to the two forms. First- and fifth-graders participated in a referential communication paradigm. Results were discussed in terms of a processing capacity model: Redundancy should facilitate performance only if it decreases processing demands on a listener. Which processing demands will be affected will depend on the specific redundancy and the specific task.I am indebted to the children and staff from Taken Elementary School in Smithtown, New York, and from Bedford, Campfield, and Westchester Elementary Schools and Pilgrim Christian Day School in Baltimore County, Maryland, for participating in this study. The first experiment was part of my doctoral dissertation at SUNY at Stony Brook. I am grateful to the members of my committee, especially Russ Whitehurst, for their guidance and advice. I also wish to thank Linda Baker for reading a preliminary draft of the paper, and Amy Gorback for running some of the subjects.     

The types of stimuli loaded in memory can modulate its effects on visual search

The effects of memory load in visual search (VS) have shown a diversity of results from the absence through beneficial and detrimental effects of a concurrent memory load in VS performance. One of the hypotheses intended to explain the heterogeneity of results follows the idea proposed by certain models in the context of VS that the contents of working memory (WM) can modulate the attentional processes involved in VS (Desimone & Duncan, 1995; Duncan & Humphreys, 1989). In four experiments, we manipulated the similarity of information maintained in WM and those materials playing the role of target and distractors in the VS task. The results showed a beneficial effect in the first two experiments, where the materials in WM matched the target in VS. However, when they matched the distractors in the attentional task there is no effect in the slope of the search function. Present results strengthen those theories supporting that visual working memory is fractionated to allow for maintenance of items not essential to the attentional task (Downing & Dodds, 2004).     

Proactive behavioral effects of theta-blocking septal stimulation in the rat

The induction of hippocampal theta rhythm using low-frequency septal stimulation has been shown to proactively (1) facilitate the acquisition and (2) increase resistance to extinction of a food-rewarded fixed-ratio (FR) bar-press response (Holt & Gray, Quarterly Journal of Experimental Psychology, 35B, 97-118, 1983). Both (1) and (2) are also seen after septal lesions. This suggests that Holt and Gray's (1983) results may have been due either to stimulation-produced theta waves (the "theta" hypothesis), or a small septal lesion produced by the stimulating current (the "lesion" hypothesis). Both hypotheses were tested in the present experiment using high-frequency septal stimulation. In one of two treatment conditions male Sprague-Dawley rats, chronically implanted with a bilateral septal stimulating electrode and a unilateral bipolar hippocampal recording electrode, received (1) trains of continuous pulses at 77 Hz which blocked the hippocampal theta rhythm, or (2) trains of pulses at 100 Hz interrupted by a 30-msec interval at a frequency of 7.7 Hz. Control animals were implanted but not stimulated. Acquisition of a discrete-trial bar-press response on a fixed ratio 5 reinforcement schedule immediately followed the treatment phase. After 15 days' acquisition all animals were extinguished over the subsequent 12 days. Results indicated that both types of septal stimulation reduced resistance to extinction of barpressing; theta-blocking stimulation produced the greater effect. Theta-blocking stimulation retarded the acquisition of bar-pressing in the early stages of training. These overall results are exactly opposite to those produced by low-frequency (7.7 Hz) theta-driving septal stimulation (Holt & Gray, 1983) and contrary to the predictions of the lesion hypothesis. Furthermore, these findings support the idea that long-term changes in behavior may depend on stimulation-produced changes in the hippocampal theta rhythm.     

The effects of different exercise types on visuospatial attention in the elderly

While the capability of visuospatial attention decreases with advanced aging, exercise is an effective primary prevention strategy to ward off the progression of such cognitive declines among the elderly. However, no studies have yet been conducted on the relationship between exercise type and visuospatial attention in the elderly. This study was thus carried out to explore the effects of open- and closed-skill exercise modes on visuospatial attention in the elderly using behavioral and cognitive electrophysiological measurements. Sixty elderly participants were divided into open-skill (n = 20), closed-skill (n = 20), or control (n = 20) groups according to their exercise-participation experience in the previous 24 months, and performed a visuospatial attention task with concomitant electrophysiological recording. The results showed that the two exercise groups (i.e., open- and closed-skill) exhibited shorter reaction times (RTs) and larger P3 amplitudes across conditions compared with the control group. Although the open- and closed-skill groups only showed approaching between-group significance on the RTs in the invalid condition and on the P3 amplitudes across conditions, only the open-skill group showed better inhibitory control of attention relative to the control group. These findings reveal the presence of neurocognitive effects on the visuospatial attention task in the two exercise groups, with significantly better performances in the open-skill group, demonstrating that regularly participating in such an exercise mode, as compared to the closed-skill one, could have more beneficial effects on visuospatial attention.     

提取干扰对不同类型内隐记忆的影响

以往研究关于提取阶段的干扰是否会影响内隐记忆存在着异义,其中一个重要因素可能源于所采用的内隐记忆测验类型的差异。本研究采用学习-测验范式,通过4个实验,分别考察了提取干扰对识别式知觉内隐测验、识别式概念内隐测验、产生式知觉内隐测验和产生式概念内隐测验的影响,以期对提取干扰和内隐记忆之间的关系有着更全面的了解。结果表明:(1)词汇判断任务(识别式知觉)和语义分类任务(识别式概念)的启动效应在提取干扰下消失了,(2)而产生式词汇判断任务(产生式知觉)和产生式语义分类任务(产生式概念)在提取干扰下仍发现了明显的启动效应,但与无干扰条件相比,启动效应量也有着明显的减少。由此可见,不同类型的内隐记忆都会受到提取干扰的影响,相比于产生式启动,识别式启动更容易受到提取干扰的破坏。     

Combining stimuli signalling response-dependent food and shock

Three rats were exposed to a multiple schedule in which separate presentations of light and tone alternated with periods during which light and tone were absent. In Phase 1, light and tone each signalled identical variable-interval schedules of food delivery. In Phase 2, light and tone signalled separate but concurrent variable-interval schedules of food and shock delivery. In both phases, the absence of light and tone was associated with the differential reinforcement of other behavior. Test presentations of light, tone, and a light-plus-tone combination indicated that in both phases, light-plus-tone controlled higher response rates than either light or tone alone. The combination continued to control enhanced responding even when the test stimuli signalled variable-interval schedules of food and fixed-ratio schedules of shock. In these latter sessions, enhanced control by the combination increased shock frequency with no corresponding change in food frequency. Apparently, the level of behavior controlled by the absence of two single stimuli may be more important than the consequences of responding in determining the effects of combined-stimulus presentations.     

The effects of different types of noise on semantic processing and syntactic reasoning

The results of four experiments showed that there was no effect of continuous noise on semantic processing and syntactic reasoning tests. However, performance on both tests was impaired when conglomerate noise, consisting of typewriting, music and unattended speech was played. It is suggested that this represents a distraction effect similar to those already reported in the literature, and this result also emphasises the importance of considering the effects of meaningful noise rather than just examining white noise of different intensities. Performance on the semantic processing test was impaired by intermittent, unpredictable noise, but this noise had no effect on the syntactic reasoning test. Possible reasons for the different effects of the intermittent noise on the two tests are put forward.