Filling a gap in the semantic gradient: Color associates and response set effects in the Stroop task

In the Stroop task, incongruent color associates (e.g., LAKE) interfere more with color identification than neutral words do (e.g., SEAT). However, color associates have historically been related to colors in the response set. Response set membership is an important factor in Stroop interference, because color words in the response set interfere more than color words not in the response set. It has not been established whether response set membership plays a role in the ability of a colorassociate to interfere with color identification. This issue was addressed in two experiments (one using vocal responses and one using manual responses) by comparing the magnitude of interference caused by color associates related to colors in the response set with that of interference caused by color associates unrelated to colors in the response set. The results of both experiments show that color associates unrelated to colors in the response set interfered with color identification more than neutral words did. However, the amount of interference was less than that from color associates that were related to colors in the response set. In addition, this pattern was consistent across response modalities. These results are discussed with respect to various theoretical accounts of Stroop interference.     

Spatial updating relies on an egocentric representation of space: Effects of the number of objects

Models of spatial updating attempt to explain how representations of spatial relationships between the actor and objects in the environment change as the actor moves. In allocentric models, object locations are encoded in an external reference frame, and only the actor’s position and orientation in that reference frame need to be updated. Thus, spatial updating should be independent of the number of objects in the environment (set size). In egocentric updating models, object locations are encoded relative to the actor, so the location of each object relative to the actor must be updated as the actor moves. Thus, spatial updating efficiency should depend on set size. We examined which model better accounts for human spatial updating by having people reconstruct the locations of varying numbers of virtual objects either from the original study position or from a changed viewing position. In consistency with the egocentric updating model, object localization following a viewpoint change was affected by the number of objects in the environment.     

Amygdala or hippocampus inactivation after retrieval induces temporary memory deficit

The hypothesis that memory is stored through a single stage of consolidation that results in a stable and lasting long-term memory has been challenged by the proposition that reactivation of a memory induces reconsolidation of the memory. The reconsolidation hypothesis is supported by evidence that, under some conditions, post-retrieval treatments affecting amygdala and hippocampus functioning impair subsequent retention performance. We now report that repeated retention testing attenuates the performance impairment induced by post-retrieval reversible inactivation of the amygdala and hippocampus of rats induced by tetrodotoxin. These findings challenge the reconsolidation hypothesis and suggest that the post-retrieval retention performance impairment is best explained as due to temporary retrieval failure.     

Cognitive load of navigating without vision when guided by virtual sound versus spatial language

A vibrotactile N-back task was used to generate cognitive load while participants were guided along virtual paths without vision. As participants stepped in place, they moved along a virtual path of linear segments. Information was provided en route about the direction of the next turning point, by spatial language ("left," "right," or "straight") or virtual sound (i.e., the perceived azimuth of the sound indicated the target direction). The authors hypothesized that virtual sound, being processed at direct perceptual levels, would have lower load than even simple language commands, which require cognitive mediation. As predicted, whereas the guidance modes did not differ significantly in the no-load condition, participants showed shorter distance traveled and less time to complete a path when performing the N-back task while navigating with virtual sound as guidance. Virtual sound also produced better N-back performance than spatial language. By indicating the superiority of virtual sound for guidance when cognitive load is present, as is characteristic of everyday navigation, these results have implications for guidance systems for the visually impaired and others.     

Effects of area and family deprivation on risk factors for teenage pregnancy among 13-15-year-old girls

Information is needed about how the effects of socio-economic deprivation on teenage pregnancy are mediated by proximal risk factors, in order to target area-wide and family interventions more effectively. Using a 2x2 factorial design, we tested the separate and interacting effects of area deprivation and family deprivation on six specific proximal risk factors for teenage pregnancy: early sexual activity, life expectations, knowledge and beliefs about contraceptives, attitude to abortion, beliefs about love, and use of local sexual health services. Data were collected from 201 13-15-year-old girls in deprived and non-deprived families living in deprived and more affluent areas of the United Kingdom. Area deprivation significantly increased early sexual activity, and both area and family deprivation significantly reduced life expectations. Significant interactions between area and family deprivation showed that the impact of living in a deprived area depends to some extent on family circumstances, with implications for targeting different types of intervention. Living in a deprived area increased early sexual activity much more markedly among girls in deprived families, so interventions to reduce early sexual activity could target individually deprived girls living in deprived areas. Living in a more affluent area increased life expectations, but only among girls in non-deprived families, so both area-wide and individually targeted interventions would be needed to raise life expectations among girls most at risk of teenage pregnancy.     

Redundant food searches by capuchin monkeys (Cebus apella): a failure of metacognition?

This study investigated capuchin monkeys' understanding of their own visual search behavior as a means to gather information. Five monkeys were presented with three tubes that could be visually searched to determine the location of a bait. The bait's visibility was experimentally manipulated, and the monkeys' spontaneous visual searches before tube selection were analyzed. In Experiment 1, three monkeys selected the baited tube significantly above chance; however, the monkeys also searched transparent tubes. In Experiment 2, a bent tube in which food was never visible was introduced. When the bent tube was baited, the monkeys failed to deduce the bait location and responded randomly. They also continued to look into the bent tube despite not gaining any pertinent information from it. The capuchin monkeys' behavior contrasts with the efficient employment of visual search behavior reported in humans, apes and macaques. This difference is consistent with species-related variations in metacognitive abilities, although other explanations are also possible.