Disrupting feedback processing interferes with rule-based but not information-integration category learning

The effect of a sequentially presented memory scanning task on rule-based and information-integration category learning was investigated. On each trial in the short feedback-processing time condition, memory scanning immediately followed categorization. On each trial in the long feedback-processing time condition, categorization was followed by a 2.5-sec delay and then memory scanning. In the control condition, no memory scanning was required. Rule-based category learning was significantly worse in the short feedback-processing time condition than in the long feedback-processing time condition or control condition, whereas information-integration category learning was equivalent across conditions. In the rule-based condition, a smaller proportion of observers learned the task in the short feedback-processing time condition, and those who learned took longer to reach the performance criterion than did those in the long feedback-processing time or control condition. No differences were observed in the information integration task. These results provide support for a multiple-systems approach to category learning and argue against the validity of single-system approaches.     

Semantic context influences memory for verbs more than memory for nouns

Three experiments revealed that memory for verbs is more dependent on semantic context than is memory for nouns. The participants in Experiment 1 were asked to remember either nouns or verbs from intransitive sentences. A recognition test included verbatim sentences, sentences with an old noun and a new verb, sentences with an old verb and a new noun, and entirely new sentences. Memory for verbs was significantly better when the verb was presented with the same noun at encoding and at retrieval. This contextual effect was much smaller for nouns. Experiments 2 and 3 replicated this effect and provided evidence that context effects reflect facilitation from bringing to mind the same meaning of a verb at encoding and at retrieval. Memory for verbs may be more dependent on semantic context because the meanings of verbs are more variable across semantic contexts than are the meanings of nouns.     

Laboratory measured behavioral impulsivity relates to suicide attempt history

The purpose of this study was to examine the relationship between laboratory behavioral measured impulsivity (using the Immediate and Delayed Memory Tasks) and suicidal attempt histories. Three groups of adults were recruited, those with either: no previous suicide attempts (Control, n = 20), only a single suicide attempt (Single, n = 20), or multiple suicidal attempts (Multiple, n = 10). As hypothesized, impulsive responses increased with the number of suicide attempts (Control < Single < Multiple). This study helps to demonstrate how laboratory behavioral measures of impulsivity can be used to discriminate groups based on suicidal histories among samples not currently exhibiting significant suicidal behaviors.     

Clark's nutcrackers (Nucifraga columbiana) and the effects of goal--landmark distance on overshadowing

Three groups of Clark's nutcrackers (Nucifraga columbiana) were trained to find a goal location defined by an array of 4 landmarks that varied in goal--landmark distance. The arrays for each group differed in the distance of the closest landmark and contained goal--landmark distances that were common across groups, allowing for the examination of the effects of both relative and absolute goal--landmark distance on encoding of a landmark array. All 3 groups readily learned the task and were subsequently tested in probe tests with only single landmarks from the array available. Search error in tests with single landmarks was compared both within and across groups. Results demonstrated that both relative and absolute goal-landmark distances are important in spatial search.     

Auditory attentional capture: effects of singleton distractor sounds

The phenomenon of attentional capture by a unique yet irrelevant singleton distractor has typically been studied in visual search. In this article, the authors examine whether a similar phenomenon occurs in the auditory domain. Participants searched sequences of sounds for targets defined by frequency, intensity, or duration. The presence of a singleton distractor that was unique on an irrelevant dimension (e.g., a low-frequency singleton in search for a target of high intensity) was associated with search costs in both detection and discrimination tasks. However, if the singleton feature coincided with the target item, search was facilitated. These results establish the phenomenon of auditory attentional capture.     

Grammatical language impairment and the specificity of cognitive domains: relations between auditory and language abilities

Grammatical-specific language impairment (G-SLI) in children, arguably, provides evidence for the existence of a specialised grammatical sub-system in the brain, necessary for normal language development. Some researchers challenge this, claiming that domain-general, low-level auditory deficits, particular to rapid processing, cause phonological deficits and thereby SLI. We investigate this possibility by testing the auditory discrimination abilities of G-SLI children for speech and non-speech sounds, at varying presentation rates, and controlling for the effects of age and language on performance. For non-speech formant transitions, 69% of the G-SLI children showed normal auditory processing, whereas for the same acoustic information in speech, only 31% did so. For rapidly presented tones, 46% of the G-SLI children performed normally. Auditory performance with speech and non-speech sounds differentiated the G-SLI children from their age-matched controls, whereas speed of processing did not. The G-SLI children evinced no relationship between their auditory and phonological/grammatical abilities. We found no consistent evidence that a deficit in processing rapid acoustic information causes or maintains G-SLI. The findings, from at least those G-SLI children who do not exhibit any auditory deficits, provide further evidence supporting the existence of a primary domain-specific deficit underlying G-SLI.     

Can semantic information be transferred between hemispheres in the split-brain?

Data from experiments with split-brain patients, who have had their left and right hemispheres disconnected, suggests a remarkable specialization of function within each hemisphere. At the same time, these patients conduct their daily lives with great proficiency. This ability suggests that some information integral to coordinated function between the hemispheres is available in the absence of the corpus callosum. Is information about the semantics of words one type of information that is shared? An experiment by suggests that it may be. Lambert reported that living/nonliving word categorization was delayed when disconnected hemispheres processed words belonging to the same category. Although other interpretations are plausible, Lambert described this effect as having a semantic source. We attempted to replicate the original effect with two additional split-brain patients, J.W. and V.P., and to extend the original design to clarify the source of the putative semantic effect. Our results indicate that any semantic interaction between the split hemispheres is not reliable. As such our study adds to the growing literature indicating that subcortical transfer of semantic information is more illusory than real.