Knowledge that Transforms

During search of the environment, the inhibition of the return (IOR) of attention to already-examined information ensures that the target will ultimately be detected. Until now, inhibition was assumed to support search of information during one processing episode. However, in some situations search may have to be completed long after it was begun. We therefore propose that inhibition can be associated with an episode encoded into memory such that later retrieval reinstates inhibitory processing and encourages examination of new information. In two experiments in which attention was drawn to face stimuli with an exogenous cue, we demonstrated for the first time the existence of long-term IOR. Interestingly. this was the case only for faces in the left visual field, perhaps because more efficient processing of faces in the right hemisphere than the left hemisphere results in richer, more retrievable memory representations.

To understand negative numbers, must we refer to positive number representations (the phylogenetic hypothesis), or do we acquire a negative mental number line (the ontogenetic hypothesis)? In the experiment reported here, participants made lateralized button responses to indicate the larger of two digits from the range -9 to 9. Digit pairs were displayed spatially congruent or incongruent with either a phylogenetic or an ontogenetic mental number line. The pattern of decision latencies suggests that negative numbers become associated with left space, thus supporting the ontogenetic view.

How does sleepiness affect selective attention? We studied the effect of circadian phase and time awake on visual search. The generalized-cognitive-slowing hypothesis predicts that search rate will be slower, feature guidance less effective, and response time (RT) lengthened when observers are sleepy. Observers performed spatial-configuration (finding a 5 among 2s) and conjunction (finding red vertical among red horizontal and green vertical) search tasks during 38 hr of wakefulness under constant conditions. Adverse circadian phases and elapsed time awake did lead to increased RT (corrected for errors). However, contrary to the hypothesis, search rates (indexed by RT x Set Size slopes) were constant across the protocol. This was true for conjunction as well as for spatial-configuration search, indicating that feature guidance was also insensitive to sleepiness. The locus of sleepiness effects on search is probably downstream from the bottleneck of attentional selection. Observers did trade accuracy for speed when sleepy. This implicates decision-stage impairments.

In four studies, we examined the spontaneous activation of specific attitudes related to social categories. These studies investigated whether priming participants with concepts associated with the elderly and skinheads influenced participants' attitudes. The results consistently demonstrated that priming a social category can influence people's attitudes such that they become more similar to those of people in the primed category. After participants were primed with the elderly category, their attitudes became more conservative; after participants were primed with the skinhead category, their attitudes became more prejudiced. We also found that these effects can occur without awareness and intention and are specific to the participants' own attitudes. The theoretical and practical implications of these findings are considered.

Research has demonstrated that oculomotor visual search is guided by memory for which items or locations within a display have already been inspected. In the study reported here, we used a gaze-contingent search paradigm to examine properties of this memory. Data revealed a memory buffer for search history of three to four items. This buffer was effected in part by a space-based trace attached to a location independently of whether the object that had been seen at that position remained visible, and was subject to interference from other stimuli seen in the course of a trial.

Here we describe the development of serial expertise in 4 experimentally naive rhesus monkeys that learned, by trial and error, the correct order in which to respond to 3-, 4-, and 7-item lists of arbitrarily selected photographs. The probabilities of guessing the correct sequence on 3-, 4-, and 7-item lists were, respectively, 1/6, 1/24, and 1/5,040. Each monkey became progressively more efficient at determining the correct order in which to respond on new lists. During subsequent testing, the subjects were presented with all possible pairs of the 28 items used to construct the four 7-item lists (excluding pairs of items that occupied the same ordinal position in different lists). Subjects responded to pairs from different lists in the correct order 91% of the time on the first trials on which these pairs were presented. These features of subjects' performance, which cannot be attributed to procedural memory, satisfy two criteria of declarative memory: rapid acquisition of new knowledge and flexible application of existing knowledge to a new problem.

Investigations of memory deficits in older individuals have concentrated on their increased likelihood of forgetting events or details of events that were actually encountered (errors of omission). However, mounting evidence demonstrates that normal cognitive aging also is associated with an increased propensity for errors of commission--shown in false alarms or false recognition. The present study examined the origins of this age difference. Older and younger adults each performed three types of memory tasks in which details of encountered items might influence performance. Although older adults showed greater false recognition of related lures on a standard (identical) old/new episodic recognition task, older and younger adults showed parallel effects of detail on repetition priming and meaning-based episodic recognition (decreased priming and decreased meaning-based recognition for different relative to same exemplars). The results suggest that the older adults encoded details but used them less effectively than the younger adults in the recognition context requiring their deliberate, controlled use.

A theory of object recognition requires a theory of shape. Despite considerable empirical and theoretical research, however, a definition of object shape has proved elusive. Two experiments provide new insights by showing that children's object recognition changes dramatically during the period between 17 and 25 months. During this time, children develop the ability to recognize stylized three-dimensional caricatures of known and novel objects. This ability is linked to the number of object names in children's vocabularies, suggesting that category learning may be a driving force behind the developmental changes.

A large body of research has shown that when people are reminded of their mortality, their defense of their cultural worldview intensifies. Although some psychological defenses seem to be instigated by negative affective responses to threat, mortality salience does not appear to arouse such affect. Terror management theory posits that the potential to experience anxiety, rather than the actual experience of anxiety, underlies these effects of mortality salience. If this is correct, then mortality-salience effects should be reduced when participants believe they are not capable of reacting to the reminder of mortality with anxiety. In a test of this hypothesis, participants consumed a placebo purported to either block anxiety or enhance memory. Then we manipulated mortality salience, and participants evaluated pro- and anti-American essays as a measure of worldview defense. Although mortality salience intensified worldview defense in the memory-enhancer condition, this effect was completely eliminated in the anxiety-blocker condition. The results suggest that some psychological defenses serve to avert the experience of anxiety rather than to ameliorate actually experienced anxiety.

Recent research in vision science, infant cognition, and word learning suggests a special role for the processing of discrete objects. But what counts as an object? Answers to this question often depend on contrasting object-based processing with the processing of spatial areas or unbound visual features. In infant cognition and word learning, though, another salient contrast has been between rigid cohesive objects and nonsolid substances. Whereas objects may move from one location to another, a nonsolid substance must pour from one location to another. In the study reported here, we explored whether attentive tracking processes are sensitive to dynamic information of this type. Using a multiple-object tracking task, we found that subjects could easily track four items in a display of eight identical unpredictably moving entities that moved as discrete objects from one location to another, but could not track similar entities that noncohesively "poured" from one location to another-even when the items in both conditions followed the same trajectories at the same speeds. Other conditions revealed that this inability to track multiple "substances" stemmed not from violations of rigidity or cohesiveness per se, because subjects were able to track multiple noncohesive collections and multiple nonrigid deforming objects. Rather, the impairment was due to the dynamic extension and contraction during the substancelike motion, which rendered the location of the entity ambiguous. These results demonstrate a convergence between processes of midlevel adult vision and infant cognition, and in general help to clarify what can count as a persisting dynamic object of attention.