Fitts’ Law as a Function of System Dynamics and Target Uncertainty

Fitts’ law was found to hold for discrete movements executed by subjects controlling the velocity of a cursor with a control stick. The slope of movement time versus index of difficulty was approximately twice as large as for a comparable position control system. Target uncertainty also increased the slope of total time versus index of difficulty, and this effect is interpreted in terms of adaptive tuning of the human movement system.     

Tolerance for distorted faces: Challenges to a configural processing account of familiar face recognition

Face recognition is widely held to rely on ‘configural processing’, an analysis of spatial relations between facial features. We present three experiments in which viewers were shown distorted faces, and asked to resize these to their correct shape. Based on configural theories appealing to metric distances between features, we reason that this should be an easier task for familiar than unfamiliar faces (whose subtle arrangements of features are unknown). In fact, participants were inaccurate at this task, making between 8% and 13% errors across experiments. Importantly, we observed no advantage for familiar faces: in one experiment participants were more accurate with unfamiliars, and in two experiments there was no difference. These findings were not due to general task difficulty – participants were able to resize blocks of colour to target shapes (squares) more accurately. We also found an advantage of familiarity for resizing other stimuli (brand logos). If configural processing does underlie face recognition, these results place constraints on the definition of ‘configural’. Alternatively, familiar face recognition might rely on more complex criteria – based on tolerance to within-person variation rather than highly specific measurement.     

Hemispheric asymmetries in processing L1 and L2 idioms: effects of salience and context

This study investigates the contribution of the left and right hemispheres to the comprehension of bilingual figurative language and the joint effects of salience and context on the differential cerebral involvement in idiom processing. The divided visual field and the lexical decision priming paradigms were employed to examine the activation of salient and nonsalient ambiguous idiom interpretations (i.e., literal vs. non-literal) in the two hemispheres. Literally plausible ambiguous idioms, L1 (Polish) and L2 (English), were embedded in unconstraining ambiguous (e.g., I knew he kept an ace up his sleeve) or constraining unambiguous context clearly favoring their conventional idiomatic interpretation (e.g., The debating president kept an ace up his sleeve). Idioms were presented centrally, followed by laterally presented targets related to the figurative (e.g., GAIN) or literal (e.g., SHIRT) meaning of the idiom and displayed at Interstimulus Intervals (ISIs) of 0 ms (Experiment 1), 300 ms (Experiment 2), and 800 ms (Experiment 3). Results indicate that context and salience effects are significantly modulated by the language (native vs. nonnative) of the stimulus materials being presented to each hemisphere. Literal facilitation was found for L2 idioms in all three ISI conditions, which supports the notion of the special status that literal meanings of L2 idioms enjoy in the course of their processing by nonnative language users. No significant differences were found between the right and left hemispheres in regards to their sensitivity to contextual constraints. Results are discussed in terms of the Graded Salience Hypothesis and the Fine/Coarse Coding Theory.     

Causes of Allais common consequence paradoxes: An experimental dissection

The common consequence paradox of Allais can be decomposed into three simpler principles: transitivity, coalescing, and restricted branch independence. Different theories attribute such paradoxes to violations of restricted branch independence only, to coalescing only, or to both. This study separates tests of these two properties in order to compare these theories. Although rank-dependent utility (RDU) theories, including cumulative prospect theory (CPT), violate branch independence, the empirical pattern of violations is opposite that required by RDU theories to account for Allais paradoxes. Data also show systematic violations of coalescing, which refute RDU theories. The findings contradict both original and CPTs with or without their editing principles of combination and cancellation. Modal choices were well predicted by Birnbaum's RAM and TAX models with parameters estimated from previous data. The effects of event framing on these tests were also assessed and found to be negligible.     

Evidence for dissociable neural mechanisms underlying inference generation in familiar and less-familiar scenarios

In this study, we investigated whether the left and right hemispheres are differentially involved in causal inference generation. Participants read short inference-promoting texts that described either familiar or less-familiar scenarios. After each text, they performed a lexical decision on a letter string (which sometimes constituted an inference-related word) presented directly to the left or right hemisphere. Response-time results indicated that hemisphere of direct presentation interacted with type of inference scenario. When test stimuli were presented directly to the left hemisphere, lexical decisions were facilitated following familiar but not following less-familiar inference scenarios, whereas when test stimuli were presented directly to the right hemisphere, facilitation was observed in both familiar and less-familiar conditions. Thus, inferences may be generated in different ways depending on which of two dissociable neural subsystems underlies the activation of background information.     

A critical boundary to the left-hemisphere advantage in visual-word processing

Two experiments explored boundary conditions for the ubiquitous left-hemisphere advantage in visual-word recognition. Subjects perceptually identified words presented directly to the left or right hemisphere. Strong left-hemisphere advantages were observed for UPPERCASE and lowercase words. However, only a weak effect was observed for AlTeRnAtInG-cAsE words, and a numerical reversal of the typical left-hemisphere advantage was observed for words in a visual prototype font (a very unfamiliar word format). Results support the theory that dissociable abstract and specific neural subsystems underlie visual-form recognition and fail to support the theory that a visual lexicon operates in the left hemisphere.     

Hemispheric processing of anaphoric inferences: the activation of multiple antecedents

This research investigates the hemispheric processing of anaphors when readers activate multiple antecedents. Participants read texts promoting an anaphoric inference and performed a lexical decision task to inference-related target words that were consistent (Experiment 1) or inconsistent (Experiment 2) with the text. These targets were preceded by constrained or less constraining text and were presented to participants' right visual field-left hemisphere or to their left visual field-right hemisphere. In Experiment 1, both hemispheres showed facilitation for consistent antecedents and the right hemisphere showed an advantage over the left hemisphere in processing antecedents when preceded by less constrained text. In Experiment 2, the left hemisphere only showed negative facilitation for inconsistent antecedents. When readers comprehend text with multiple antecedents: both hemispheres process consistent information, the left hemisphere inhibits inconsistent information, and the right hemisphere processes less constrained information.     

Interfering with memory for faces: The cost of doing two things at once

We inferred the processes critical for episodic retrieval of faces by measuring susceptibility to memory interference from different distracting tasks. Experiment 1 examined recognition of studied faces under full attention (FA) or each of two divided attention (DA) conditions requiring concurrent decisions to auditorily presented letters. Memory was disrupted in both DA relative to FA conditions, a result contrary to a material-specific account of interference effects. Experiment 2 investigated whether the magnitude of interference depended on competition between concurrent tasks for common processing resources. Studied faces were presented either upright (configurally processed) or inverted (featurally processed). Recognition was completed under FA, or DA with one of two face-based distracting tasks requiring either featural or configural processing. We found an interaction: memory for upright faces was lower under DA when the distracting task required configural than featural processing, while the reverse was true for memory of inverted faces. Across experiments, the magnitude of memory interference was similar (a 19% or 20% decline from FA) regardless of whether the materials in the distracting task overlapped with the to-be-remembered information. Importantly, interference was significantly larger (42%) when the processing demands of the distracting and target retrieval task overlapped, suggesting a processing-specific account of memory interference.     

Functional lateralization, interhemispheric transfer and position bias in serial reversal learning in pigeons (Columba livia)

In the present study we investigated lateralization of color reversal learning in pigeons. After monocular acquisition of a simple color discrimination with either the left or right eye, birds were tested in a serial reversal procedure. While there was only a slight and non-significant difference in choice accuracy during original color discrimination, a stable superiority of birds using the right eye emerged in serial reversals. Both groups showed a characteristic ‘learning-to-learn’ effect, but right-eyed subjects improved faster and reached a lower asymptotic error rate. Subsequent testing for interocular transfer demonstrated a difference between pre- and post-shift choice accuracy in pigeons switching from right to left eye but not vice versa. This can be accounted for by differences in maximum performance using either the left or right eye along with an equally efficient but incomplete interocular transfer in both directions. Detailed analysis of the birds’ response patterns during serial reversals revealed a preference for the right of two response keys in both groups. This bias was most pronounced at the beginning of a session. It decreased within sessions, but became more pronounced in late reversals, thus indicating a successful strategy for mastering the serial reversal task. Interocular transfer of response patterns revealed an unexpected asymmetry. Birds switching from right to left eye continued to prefer the right side, whereas pigeons shifting from left to right eye were now biased towards the left side. The results suggest that lateralized performance during reversal learning in pigeons rests on a complex interplay of learning about individual stimuli, stimulus dimensions, and lateralized response strategies. Received: 4 June 1999 / Accepted after revision: 18 August 1999     

Mediation and Causality at the Individual Level

Within a person-oriented research paradigm the focus is on individuals characterized by patterns of information that are regarded as indivisible wholes. It is then not sufficient to carry out standard variable-oriented mediation analysis. The procedure suggested by von Eye, Mun, and Mair (2009) for pattern-oriented mediation analysis is much better aligned to this person-oriented framework. An important new feature in their approach is that it can detect mediator configurations that prohibit predictor and outcome connections at a pattern level. Two extensions of their procedure are suggested, namely (1) the use of cluster analysis to arrive at the categories and (2) the use of other models for estimating the expected frequencies. It is pointed out that in their context a functional relations perspective might be more relevant than the standard causality perspective.