Behavioral measures of attention and cognitive control during a new auditory working memory paradigm.

Proactive control is the ability to manipulate and maintain goal-relevant information within working memory (WM), allowing individuals to selectively attend to important information while inhibiting irrelevant distractions. Deficits in proactive control may cause multiple cognitive impairments seen in schizophrenia. However, studies of cognitive control have largely relied on visual tasks, even though the functional deficits in schizophrenia are more frequent and severe in the auditory domain (i.e., hallucinations). Hence, we developed an auditory analogue of a visual ignore/suppress paradigm. Healthy adults (N = 40) listened to a series of four letters (600-ms stimulus onset asynchrony) presented alternately to each ear, followed by a 3.2-s maintenance interval and a probe. Participants were directed either to selectively ignore (I) the to-be-presented letters at one ear, to suppress (S) letters already presented to one ear, or to remember (R) all presented letters. The critical cue was provided either before (I) or after (S) the encoding series, or simultaneously with the probe (R). The probes were encoding items presented to either the attended/not suppressed ear ("valid") or the ignored/suppressed ear ("lure"), or were not presented ("control"). Replicating prior findings during visual ignore/suppress tasks, response sensitivity and latency revealed poorer performance for lure than for control trials, particularly during the suppress condition. Shorter suppress than remember latencies suggested a behavioral advantage when discarding encoded items from WM. The paradigm-related internal consistencies and 1-week test-retest reliabilities (n = 38) were good to excellent. Our findings validate these auditory WM tasks as a reliable manipulation of proactive control and set the stage for studies with schizophrenia patients who experience auditory hallucinations.

Parallel effects of retrieval ease on attributions about the past and the future.

The present study explored the role of task difficulty in judgments about the past and the future. Participants recalled events from childhood and imagined future events. The difficulty of the task was manipulated by asking participants to generate either four or twelve events. Participants then rated how well they could generally remember events from their childhood or how well planned their futures were. Consistent with past research (e.g., Winkielman, Schwarz, & Belli, 1998), participants in the difficult recall group rated their childhood memories as less complete than participants in the easy recall group. A parallel effect was found in participants' judgments of their futures. Participants who were asked to imagine twelve future events rated their future plans as less complete than those who imagined four events. Moreover, there was a negative correlation between the rated difficulty of the task and the degree to which participants found their memories and plans to be complete. We also examined the valence of the generated events. These results showed a strong positivity bias for both types of judgments, and the bias was particularly strong when thinking of future events. The results suggest that similar attributional processes mediate beliefs about the past and the future.

An Event-Related Potential study of letter spacing during visual word recognition.

Increasing spacing between letters in words (e.g., s p a c e vs. space) helps children and adults read more fluidly and with fewer errors. This effect has been demonstrated behaviorally, chiefly through lexical decision reaction time and total paragraph reading time. To date, however, no electrophysiological work has examined the letter spacing effect, resulting in little insight regarding how letter spacing impacts "hidden" levels of processing between apprehension of the word form and the final behavioral outcome. Here, we examined how varying levels of interletter spacing (crowded, standard, and increased) impact ERPs elicited by words and other item types (pseudowords, illegal strings, and a false font). Results indicate that letter spacing does not impact the ERP within the first second after viewing a wordform, but that it does have downstream effects as indicated by data collected using a priming design. Further, the facilitation of downstream processing afforded by increased spacing seems to be greater for more word-like stimuli (e.g., greater for words than for consonant strings, etc). Results are discussed as being somewhat inconsistent with prevalent views of the mechanism of the letter spacing effect (i.e., crowding).

An event-related potential study of the relationship between N170 lateralization and phonological awareness in developing readers.

As reading development progresses, the visual processing of word forms becomes increasingly left-lateralized. This is visible, among other ways, as increased left-lateralization of the N170 ERP component. A primary explanation of this effect, the phonological mapping hypothesis, proposes that the left-lateralization of visual word form processing that accompanies reading development is the result of calling upon left hemisphere auditory language regions to perform the linking of orthography with phonology (phonological mapping). A key, but untested, prediction of the phonological mapping hypothesis is thus that individuals with greater phonological awareness should exhibit more left lateralized visual processing of word forms than individuals with poorer phonological awareness. We set out to test this hypothesis here. We accomplished this by collecting ERPs while children grades 5-6 viewed words, objects, and word/object ambiguous items (e.g., "SMILE" shaped like a smile - hereafter referred to as wobjects). Results revealed that, consistent with the phonological mapping hypothesis, individual phonological awareness (but not other measures of reading development) predicted left-lateralization of the N170 component elicited in response to words (but not item types that were not word-like).

Individual differences in involvement of the visual object recognition system during visual word recognition.

Individuals with dyslexia often evince reduced activation during reading in left hemisphere (LH) language regions. This can be observed along with increased activation in the right hemisphere (RH), especially in areas associated with object recognition - a pattern referred to as RH compensation. The mechanisms of RH compensation are relatively unclear. We hypothesize that RH compensation occurs when the RH object recognition system is called upon to supplement an underperforming LH visual word form recognition system. We tested this by collecting ERPs while participants with a range of reading abilities viewed words, objects, and word/object ambiguous items (e.g., "SMILE" shaped like a smile). Less experienced readers differentiate words, objects, and ambiguous items less strongly, especially over the RH. We suggest that this lack of differentiation may have negative consequences for dyslexic individuals demonstrating RH compensation.