Practice effects in backward masking.

In two experiments we demonstrate that much larger practice effects occur in a backward masking paradigm where patterned masks are used than in similar visual processing paradigms, such as lateral masking and whole report. In additional experiments we examine four possible explanations for the large practice effects: increased familiarity with the paradigm in general, learning about the targets, learning about the masks, and enhanced sensory processing. Because of failure to observe similar practice effects in related paradigms not involving backward masking and because of the sustained nature of the improvement, we reject the first explanation as a source of practice effect. Experiment 3 allowed us to reject target learning as a source of improvement as well; target sets were switched at the end of training, but no decrement in performance was observed. In Experiment 4, mask sets were switched at the end of training, revealing a significant decrement in performance. Learning about the specific masks, then, does contribute to the observed improvement. However, it is responsible for only about one third of the overall improvement in performance. The final experiment provides evidence that the residual improvement is due to enhanced sensory processing. In that experiment, training on backward masking led to a lowered threshold in a two-flash paradigm but not to a significant change in whole-report performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual signal detectability with two noise components: anomalous masking effects

We measured human observers' detectability of aperiodic signals in noise with two components (white and low-pass Gaussian). The white-noise component ensured that the signal detection task was always noise limited rather than contrast limited (i.e., image noise was always much larger than observer internal noise). The low-pass component can be considered to be a statistically defined background. Contrast threshold elevation was not linearly related to the rms background contrast. Our results gave power-law exponents near 0.6, similar to that found for deterministic masking. The Fisher-Hotelling linear discriminant model assessed by Rolland and Barrett [J. Opt. Soc. Am. A 9, 649 (1992)] and the modified nonprewhitening matched filter model suggested by Burgess [J. Opt. Soc. Am. A 11, 1237 (1994)] for describing signal detection in statistically defined backgrounds did not fit our more precise data. We show that it is not possible to find any nonprewhitening model that can fit our data. We investigated modified Fisher-Hotelling models by using spatial-frequency channels, as suggested by Myers and Barrett [J. Opt. Soc. Am. A 4, 2447 (1987)]. Two of these models did give good fits to our data, which suggests that we may be able to do partial prewhitening of image noise.     

Influence of age on practice effects in longitudinal neurocognitive change.

Objective: Longitudinal comparisons of neurocognitive functioning often reveal stability or age-related increases in performance among adults under about 60 years of age. Because nearly monotonic declines with increasing age are typically evident in cross-sectional comparisons, there is a discrepancy in the inferred age trends based on the two types of comparisons. The current research investigated the role of practice effects in longitudinal comparisons on the discrepancy. Method: Longitudinal data over an average interval of 2.5 years were available on five abilities (i.e., reasoning, spatial visualization, episodic memory, perceptual speed, vocabulary) in a sample of 1,616 adults ranging from 18 to over 80 years of age. Practice effects were estimated from comparisons of the performance of people of the same age tested for either the first or second time, after adjusting for the possibility of selective attrition. Results: Increased age was associated with significantly more negative longitudinal changes with each ability. All of the estimated practice effects were positive, but they varied in magnitude across neurocognitive abilities and as a function of age. After adjusting for practice effects the longitudinal changes were less positive at younger ages and slightly less negative at older ages. Conclusions: It was concluded that some, but not all, of the discrepancy between cross-sectional and longitudinal age trends in neurocognitive functioning is attributable to practice effects positively biasing the longitudinal trends. These results suggest that the neurobiological substrates of neurocognitive functioning may change across different periods in adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast discrimination, non-uniform patterns and change blindness

Change blindness--our inability to detect large changes in natural scenes when saccades, blinks and other transients interrupt visual input--seems to contradict psychophysical evidence for our exquisite sensitivity to contrast changes. Can the type of effects described as 'change blindness' be observed with simple, multi-element stimuli, amenable to psychophysical analysis? Such stimuli, composed of five mixed contrast elements, elicited a striking increase in contrast increment thresholds compared to those for an isolated element. Cue presentation prior to the stimulus substantially reduced thresholds, as for change blindness with natural scenes. On one hand, explanations for change blindness based on abstract and sketchy representations in short-term visual memory seem inappropriate for this low-level image property of contrast where there is ample evidence for exquisite performance on memory tasks. On the other hand, the highly increased thresholds for mixed contrast elements, and the decreased thresholds when a cue is present, argue against any simple early attentional or sensory explanation for change blindness. Thus, psychophysical results for very simple patterns cannot straightforwardly predict results even for the slightly more complicated patterns studied here.     

Contrast, contradiction, and change in psychotherapy.

The experience of contrast not only plays a fundamental role in moment-to-moment construction of reality, but also may function as a common source of change across diverse forms of psychotherapy. This article (1) examines salient sources of contrast associated with psychodynamic, interpersonal, behavioral, cognitive–behavioral, and experiential psychotherapies and (2) proposes a developmental framework for understanding the role of contrast in the process of change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Potential masking effects of salmeterol on airway inflammation in asthma

We hypothesized that regular use of long-acting beta-agonists could delay recognition of ("mask") increasing airway inflammation. We studied steroid-sparing and "masking" effects of salmeterol versus placebo in 13 asthmatic individuals requiring >= 1,500 microgram inhaled corticosteroid daily. Corticosteroid doses were reduced weekly until criteria were met for an exacerbation or the corticosteroid was fully withdrawn. Subjects were restabilized on their original dose of inhaled corticosteroid for 4 wk before crossover to the alternative treatment. Subjects maintained symptom and peak expiratory flow (PEF) diaries, and underwent weekly spirometric, methacholine challenge, sputum eosinophil, and serum eosinophil cationic protein (ECP) measurements. Mean corticosteroid dose was reduced by 87% during salmeterol treatment, versus 69% with placebo (p = 0.04). Sputum eosinophils increased before exacerbation despite stable symptoms, FEV1, and PEF. In the week before clinical exacerbation, sputum eosinophil counts were higher in the salmeterol-treatment arm (19.9 +/- 29.8% [mean +/- SD], versus placebo 9.3 +/- 17.6%; p = 0.006). Five subjects showed > 10% sputum eosinophilia before exacerbation during salmeterol treatment, as compared with two receiving placebo. In this model, salmeterol controlled symptoms and lung function until inflammation became significantly more advanced. We conclude that the bronchodilating and symptom-relieving effects of salmeterol can mask increasing inflammation and delay awareness of worsening asthma.     

On the selective effects of a patterned masking stimulus.

Investigated previous findings which suggest that a patterned masking stimulus, presented immediately following tachistoscopic presentation of letter rows, produces large decrements in the recall of letters from the central positions in the rows but has little effect on recall from either end of the displays. 4 experiments with 92 undergraduate Ss confirm the existence of a selective masking effect. The effect was obtained following exposure durations which varied from 30-200 msec. and with both full- and partial-report techniques. Also the selective masking effect was limited to multiletter displays in that it was shown that single letters were masked equally well across the positions used for an entire row. Results suggest that both ends of multiletter displays are processed and identified before the center positions of the displays are processed. (French summary) (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Combining simultaneous with temporal masking.

Simultaneous and temporal masking are two frequently used techniques in psychology and vision science. Although there are many studies and theories related to each masking technique, there are no systematic investigations of their mutual relationship, even though both techniques are often applied together. Here, the authors show that temporal masking can both undo and enhance the deteriorating effects of simultaneous masking depending on the stimulus onset asynchrony between the simultaneous and temporal masks. For the task and stimuli used in this study, temporal masking was largely unaffected by the properties of the simultaneous mask. In contrast, simultaneous masking seems to depend strongly on spatial grouping and was strongly affected by the properties of the temporal mask. These findings help to identify the nature of both temporal and simultaneous masking and promote understanding of the role of spatial and temporal grouping in visual perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast and accentuation effects in category learning.

This study examines the accentuation of perceived intercategory differences. In Experiment 1, 2 sets of trait adjectives were presented, a neutral set and a set of either favorable traits or unfavorable traits. Ss estimated the mean favorability of each set. The mean favorability of the neutral set was then increased or decreased by adding new traits. As predicted, the estimated mean favorability of the neutral set changed more when the set became more distinct from a contextual set than when it became more similar. In Experiment 2, estimated category means were displaced away from each other (contrast effect), and they moved even farther apart when new information increased the variability of trait favorability (accentuation effect). This change was illusory because the actual category means remained constant. Experiment 3, in which trait adjectives described members of 2 novel groups, replicated Experiment 2. The relevance of contrast and accentuation effects to the development and maintenance of differentiated intergroup perceptions is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast effects in escape conditioning of rats.

In Exp I 39 male Holtzman albino rats ran for 20 trials from an alley where they received .2-, .4-, or .8-ma shocks to a goal box where there was no shock. All Ss were then shifted to .4 ma in the alley for 20 trials. Results show that rapid adjustment of running speeds occurred with shifts in amount of escapable shock. More importantly, however, positive and negative contrast occurred. In Exp I an experimental group (n = 10) received .2 ma on half of the trials and .4 ma on the other half, and 2 control groups (n = 10) received either .4 or .2 ma on all trials. Results show that the experimental group escaped faster on .4-ma trials than the .4-ma control group (positive contrast) and escaped more slowly on .2-ma trials than the .2-ma control (negative contrast). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Persistence of stimulus-response compatibility effects with extended practice.

The influence of extended practice on stimulus–response (S–R) compatibility effects was investigated. Three experiments, each extending over a period of 8 sessions, were conducted. The nature and degree of compatibility were manipulated across experiments. In all experiments, a persistent effect of S–R compatibility on reaction times (RTs) was observed. Thus, the lower bound for RTs appears to be less for compatible assignments than for incompatible assignments. This persistence of S–R compatibility indicates that the initial codings used to perform a novel task continue to exert an influence on later performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Masking by object substitution: Dissociation of masking and cuing effects.

In a newly discovered form of visual masking, a target stimulus is masked by 4 flanking dots if their offset is delayed relative to the target (V. Di Lollo, J. T. Enns, & R. A. Rensink, 2000). In Di Lollo et al. (2000), the dot pattern also cued the relevant target and therefore required deliberate attention. In the present Experiments 2-6, a central arrow cued 1 of 2 letters for an E/F discrimination, with dots flanking both letters. Masking was reduced compared with the mask-cue procedure but was still robust. Delayed-offset dots flanking the nontarget also impaired performance, indicating competition for attention. Masking was unaffected by brightness of the dots relative to the target. Masking was attenuated not only by precuing attention to the target location but also by preview of an uninformative dot mask. Theories of masking by object substitution must therefore accommodate the prior context into which the target stimulus is introduced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast and convergence effects in ratings of foods.

"A set of assumptions was made that led to the hypothesis that preference ratings for poor quality food will be lower when preceded by a good quality food than when preceded by another poor quality item (contrast effects). It was also hypothesized that preference for a good quality food will be higher when preceded by another good quality item than when preceded by a poor quality product (convergence effects). The other predictions were that preference will increase with successive presentations of the same quality item, provided no opposite quality intervenes. The predictions concerning preference for the poor quality foods were clearly confirmed, but those involving the good quality foods were not substantiated." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Backward masking.

In backward masking, perception of a test stimulus is suppressed by masking stimulation that is presented subsequently. Psychophysical studies of this phenomenon have utilized visual, auditory, and cutaneous stimuli. These masking studies are reviewed and their results discussed in terms of possible neural mediating mechanisms. (88 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast effects in spontaneous evaluations: A psychophysical account.

In the affective-priming paradigm, target stimuli are preceded by evaluatively polarized prime stimuli and then are to be classified as either good or bad as fast as possible. The typical and robust finding is assimilation: Primes facilitate the processing of evaluatively consistent targets relative to evaluatively inconsistent targets. Nevertheless, contrast effects have repeatedly been observed. The authors propose a new psychophysical account of normal (assimilative) and reversed (contrastive) priming effects and test new predictions derived from it in 5 studies: In Studies 1 and 2, the authors' account is shown to provide a better explanation of contrastive effects in a priming paradigm with two primes than the traditional attentional account does. Furthermore, as predicted by the new account, contrast effects emerge at an intermediate stimulus-onset asynchrony (SOA, Study 3) and even with short SOAs when target onset takes participants by surprise (Study 4). Finally, the use of extremely valenced primes triggers corrective efforts (Study 5) as predicted. Implications for priming measures of evaluative associations are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Putting judgments of control into context: Contrast effects.

We tested predictions derived from the contrast literature concerning the influence of context on judgments of control. In Experiments 1–3, some Ss 1st completed a judgment of control task in which there was a relatively high degree of response-outcome contingency and then completed a task in which there was a moderate contingency. Other Ss 1st completed a task in which there was response-outcome noncontingency, then one in which there was a moderate contingency. The mean judgment of control rating for the moderate contingency task of the 1st group of Ss was reliably lower than that for the same task of the 2nd group. In Experiment 4, we increased the amount of initial exposure to the high or low contingency tasks. The judgments on the moderate contingency task still showed the same pattern as observed in Experiments 1–3. In Experiment 5, we found that the contrast effects observed in the prior experiments were eliminated when Ss did not complete a judgment scale following the 1st contingency problem (A. Pepitone and M. DiNuble; see record 1976-27744-001). Implications of the findings for existing theories and for future theoretical development are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contrast effects do not underlie effects of preceding liquids on stop-consonant identification by humans.

These experiments explored the claim by A. Lotto and K. Kluender (1998) that frequency contrast explains listeners' compensations for coarticulation in the case of liquid consonants coarticulating with following stops. Evidence of frequency contrast in experiments that tested for it directly was not found, but Lotto and Kluender's finding that high- and low-frequency precursor tones can produce contrastive effects on stop-consonant judgments were replicated. The effect depends on the amplitude relation of the tones to the third formant (F3) of the stops. This implies that the tones mask F3 information in the stop consonants. It is unknown whether liquids and following stops in natural speech are in an appropriate intensity relation for masking of the stop. A final experiment, exploiting the McGurk effect, showed compensation for coarticulation by listeners when neither frequency contrast nor masking can be the source of the compensations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Unwanted drug effects in clinical practice

BACKGROUND AND OBJECTIVE: Unwanted drug reactions (UDR) in routine clinical practice remain largely unrecorded, even though such documentation can significantly contribute to quality assurance in drug therapy. This prospective study was undertaken to ascertain within a defined time period the frequency and significance of UDR in the medical wards of a general hospital (focus on gastroenterology) and find the organisational structures needed for its documentation. PATIENTS AND METHODS: All observed UDRs among a total of 4032 in-patients were recorded on a simple registration form, filled in by doctors assigned to collect the information, which was then analysed in cooperation with the Drug Commission of the German Medical Council (AKdA). RESULTS: UDRs were recorded in 315 patients (7.8%), 135 of them (43%) already present on admission. 101 patients had been admitted because of the UDR. Gastrointestinal disorders, particularly peptic ulcer, and skin rash were the most common UDRs. Individual drugs most frequently responsible were acetylsalicylic acid, cyclophosphamide and digoxin, the most common drug groups were nonsteroid analgesics, antibiotics and cytostatic drugs. The method employed proved to be practicable and cost-effective. CONCLUSIONS: A simple and cost-effective system, integrated into the daily medical routine, can heighten awareness of UDRs among doctors and thus improve drug safety in hospitals, while concomitantly providing an important feature of further medical education.     

Selective forward masking.

Assessed the effects of masking on recall accuracy in 2 experiments with a total of 28 male undergraduates. When a patterned masking stimulus was presented immediately before a centrally-fixated, tachistoscopically-presented 7-letter row (forward masking), a selective effect on recall accuracy was found, as measured by a partial-report technique. There was greater masking of the end letters than of the center letters in the displays. When the masking stimulus was presented immediately after the presentation of a letter row (backward masking), the results confirmed previous findings of greater masking of the center letters than the end letters. These different selective effects of forward and backward masking are consistent with the assumption that the processing of multiletter displays begins at the ends of the letter rows. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)