Evidence accumulation in the integrated and primed Stroop tasks

We report distributional analyses of response times (RT) in two variants of the color-word Stroop task using manual keypress responses. In the classic Stroop task, in which the color and word dimensions are integrated into a single stimulus, the Stroop congruence effect increased across the quantiles. In contrast, in the primed Stroop task, in which the distractor word is presented ahead of colored symbols, the Stroop congruence effect was manifested solely as a distributional shift, remaining constant across the quantiles. The distributional-shift pattern mirrors the semantic-priming effect that has been reported in semantic categorization tasks. The results are interpreted within the framework of evidence accumulation, and implications for the roles of task conflict and informational conflict are discussed.     

Lateralized cognition: asymmetrical and complementary strategies of pigeons during discrimination of the "human concept"

This study was aimed at revealing which cognitive processes are lateralized in visual categorizations of "humans" by pigeons. To this end, pigeons were trained to categorize pictures of humans and then tested binocularly or monocularly (left or right eye) on the learned categorization and for transfer to novel exemplars (Experiment 1). Subsequent tests examined whether they relied on memorized features or on a conceptual strategy, using stimuli composed of new combinations of familiar and novel humans and backgrounds (Experiment 2), whether the hemispheres processed global or local information, using pictures with different levels of scrambling (Experiment 3), and whether they attended to configuration, using distorted human figures (Experiment 4). The results suggest that the left hemisphere employs a category strategy and concentrates on local features, while the right hemisphere uses an exemplar strategy and relies on configuration. These cognitive dichotomies of the cerebral hemispheres are largely shared by humans, suggesting that lateralized cognitive systems already defined the neural architecture of the common ancestor of birds and mammals.     

Modulation of regularity and lexicality effects in reading aloud

We examined the question of whether the sizes of the regularity and lexicality effects in naming can be modulated as a function of filler type (nonwords or low-frequency exception words). The lexicality effect was larger in the exception word filler condition than in the nonword filler condition, but the size of the regularity effect was essentially unaffected by filler type. This pattern is at odds with what is generally assumed to be the predictions from dual-route theories of reading aloud. An attempt was next made to determine whether the dual-route cascaded model of Coltheart, Rastle, Perry, Langdon, and Ziegler (2001) could possibly simulate this pattern when changes were introduced to each of the three parameters that affect the contribution of the nonlexical route. We discuss the implications of these results for the idea that reliance on the lexical and nonlexical routes is under strategic control.     

Cross-task strategic effects

When easy and difficult items are mixed together, their reading aloud latencies become more homogeneous relative to their presentation in unmixed ("pure") conditions (Lupker, Brown, & Colombo, 1997). We report two experiments designed to investigate the nature of the mechanism that underlies this list composition, or blocking, effect. In Experiment 1, we replicated Lupker et al.'s (1997) blocking effect in the reading aloud task and extended these findings to the visual lexical decision task. In Experiment 2, we found that blocking effects generalized across tasks: The characteristics of stimuli in a visual lexical decision task influenced reading aloud latencies, and vice versa, when visual lexical decision and reading aloud trials were presented alternately in the same experiment. We discuss implications of these results within time-criterion (Lupker et al., 1997) and strength-of-processing (Kello & Plaut, 2000, 2003) theories of strategic processing in reading.     

Priming and attentional control of lexical and sublexical pathways in naming: a reevaluation

The authors report 3 naming experiments using J. D. Zevin and D. A. Balota's (2000) multiple prime manipulation. They used 2 sets of nonword primes (fast and slow) and low-frequency exception word primes to separate the effects of prime speed from those of prime type. The size of the regularity effect was unaffected by prime type. Relative to the low-frequency exception word prime condition, the frequency effect was reduced in the fast, but not in the slow, nonword prime condition. Lexicality effect size was reduced in both nonword prime conditions, a result consistent with the lexical checking strategy described by S. J. Lupker, P. Brown, and L. Colombo (1997). The authors suggest that these results are better explained in terms of S. J. Lupker et al.'s time-criterion account than J. D. Zevin and D. A. Balota's pathway control hypothesis.     

Two bases of the compatibility effect in the Implicit Association Test (IAT)

Four experiments are reported, investigating the mechanisms underlying the compatibility effect in the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998). All experiments involved two IATs: flower IAT, in which the target categories were flowers and insects, and number IAT, involving even and odd numbers as target categories. In Experiment 1, using the standard IAT procedure, the two IATs produced equal IAT effects, despite large differences in rated valence contrast between flowers and insects and between even and odd numbers. Experiment 2 used a procedure developed by Klauer and Mierke (2005) and produced results consistent with the view that valence plays a role in the flower IAT but not in the number IAT. Experiments 3 and 4 used manipulations similar to those developed by Rothermund and Wentura (2004) and showed that these manipulations affected the flower IAT and number IAT differently. The results provide converging evidence that the two types of IAT effects-one based on valence and one based on familiarity-are empirically dissociable.Experiments 1and 2 reported in this paper were conducted as an honours project by Marie Peek-O'Leary under the supervision of Sachiko Kinoshita. Parts of this paper were presented at the 44th Annual Meeting of the Psychonomic Society held in Vancouver, Canada, in November, 2003.     

Contributors to suicidal ideation among bipolar patients with and without a history of suicide attempts

This study was designed to develop models for vulnerability to suicidal ideation in bipolar patients. Logistic regression models examined correlates of suicidal ideation in patients who had versus had not attempted suicide previously. Of 477 patients assessed, complete data on demographic, illness history, and personality variables were available on 243. The regression models achieved positive predictive values of 55% and 59% for the attempter (N = 92) and nonattempter groups (N = 151), respectively. Depression was cross-sectionally associated with suicidal ideation in both the attempter and nonattempter groups but made a smaller contribution among attempters. Poor psychosocial adaptation and the personality factor "openness" were stronger contributors to suicidal ideation among prior attempters while anxiety and extraversion appeared protective against ideation. Among nonattempters, depression, anxiety, and neuroticism were the predominant influences on suicidal ideation. Bipolar patients with suicidal ideation may benefit from different treatment strategies depending on their prior attempt status.     

Effects of filler type in naming: change in time criterion or attentional control of pathways?

We report two naming experiments examining the effects of filler type on the size of regularity and frequency effects. Low-frequency exception words were used as one filler type in both experiments. Their effects were contrasted with the effects of nonword fillers (Experiment 1) and low-frequency regular word fillers (Experiment 2). In both experiments, the size of the regularity effect was unaffected by the filler type manipulation. In contrast, the frequency effect interacted with filler type such that relative to the low-frequency exception filler environment, the size of the frequency effect was reduced in the environment of low frequency regular word fillers, but not in the environment of nonword fillers. These results appear to be better explained in terms of Lupker, Brown, and Colombo's (1997) flexible time-criterion framework than in terms of a pathway control hypothesis (e.g., Zevin & Balota, 2000).     

Rapid acceleration of the lower arm correlates with agonist EMGs during the initial phase

Fifty-eight healthy subjects made rapid elbow extensions to a target over 54 degrees. Angular acceleration was measured and surface electromyograms (EMGs) were recorded from the antagonistic muscles using monopolar rather than bipolar electrode configurations. Marked individual differences were found in the peak value of the first derivative of acceleration (dAcc/dt_Pk). The dAcc/dt_Pk correlated with both quantitative and qualitative properties of the agonist EMGs, but not with those of the antagonist EMG. The agonist EMGs, integrated until the moment of dAcc/dt_Pk, were positively correlated with dAcc/dt_Pk. The interval between EMG onset and EMG peak decreased with increasing dAcc/dt_Pk. The duration of the initial negative phase in the EMGs, which was considered to index the time required to recruit high-threshold MUs, decreased with increasing dAcc/dt_Pk. The results indicate that the ability to rapidly accelerate the lower arm varies across subjects, probably due in part to individual differences in the neural capacity to drive the agonists.