The linear separability effect in color visual search: Ruling out the additive color hypothesis

Bauer, Jolicoeur, and Cowan (1996b, 1996c) demonstrated difficult visual search for color targets that were not linearly separable (in color space) from two distractor colors and easier search for linearly separable targets. This suggested that search is mediated by a chromatically linear discrimination mechanism (see D’Zmura, 1991). However, in those experiments, the targets that were not linearly separable fell midway between the distractor colors and thus corresponded to the admix of the distractor colors. An alternate interpretation of the results of Bauer et al. is that search was more difficult when the target corresponded to the distractor admix than when it did not. We tested this hypothesis in three experiments by contrasting conditions in which a target that was not linearly separable did or did not correspond to the admix of the distractor colors. In all cases, a target that was not linearly separable produced difficult search, demonstrating that linear separability determines search performance.     

The format of representation of recognized words in infants' early receptive lexicon

Eleven-month-olds can recognize a few auditorily presented familiar words in experimental situations where no hints are given by the intonation, the situation, or the presence of possible visual referents. That is, infants of this age (and possibly somewhat younger) can recognize words based on sound patterns alone. The issue addressed in this article is what is the type of mental representations infants use to code words they recognize. The results of a series of experiments with French-learning infants indicate that word representations in 11-month-olds are segmentally underspecified and suggest that they are all the more underspecified when infants engage in recognizing words rather than merely attending to meaningless speech sounds. But underspecification has limits, which were explored here with respect to word-initial consonants. The last two experiments show the way to investigating further these limits for word-initial consonants as well as for segments in other word positions. In French, infants' word representations are flexible enough to allow for structural changes in the voicing or even in the manner of articulation of word-initial consonants. Word-initial consonants must be present, however, for words to be recognized. In conclusion, a parallel is proposed between the emerging capacities to ignore variations that are irrelevant for word recognition in a “lexical mode” and to ignore variations that are phonemically irrelevant in a “neutral mode” of listening to native speech.     

Perceptual versus postperceptual mediation of visual context effects: Evidence from the letter-superiority effect

Two experiments demonstrated letter-context effects that cannot easily be accounted for by post-perceptual theories based on structural redundancy, figural goodness, or memory advantage. In Experiment 1, subjects identified the color of a letter fragment more accurately in letter than in nonletter contexts. In Experiment 2, subjects identified the feature presented in a precued color more accurately in letters than in nonletters. We argue that these effects result from top-down perceptual processing.     

LES DIMENSIONS DE LA DETRESSE PSYCHOLOGIQUE: ANALYSE FACTORIELLE CONFIRMATOIRE DE TYPE HIERARCHIQUE*

The study of the hierarchical organization of psychological distress dimensions is plagued by numerous theoretical and methodological problems. The researcher must take into account the respective value of unidimensional and multidimensional conceptualizations and the complex debates between factor analysis experts. The main purpose of the present study is to demonstrate the construct validity of a hierarchical model of psychological distress. The sample consisted of 150 outpatients of the University of Montreal Psychology Clinic which completed the Psychiatric Symptoms Inventory. The results of first-order and second-order confirmatory factor analyses show the value of a hierarchical conceptualization of psychological distress. However, an examination of normalized residuals, total direct effects and modification indexes reveals the inadequacy of some items from the anxiety and cognitive problems subscales. The theoretical implications of these results are discussed.     

Is the concept of ‘personality’ relevant to the study of animal aggression?

Both theoretical considerations and methodological constraints explain why the experimental study of animal aggression does not often put much emphasis on individual differences and hardly uses the concept of ‘personality’. And yet, if neurobiologists consider those brain mechanisms that underlie the interpretation of a given situation and the anticipation of a method to cope with it, they are led to investigate mechanisms that underlie a number of behaviour dimensions which the psychologist would refer to as ‘personality’. The actual object considered in either case does not essentially differ. This is exemplified more concretely by examining the kind of factors—and the brain mechanisms involved in their very existence or in their processing—that contribute to determine the probability that in the face of a given situation, a given individual will adopt aggressive behaviour as the coping strategy.     

International perspectives in psychological research

The following two papers by (1) Bond and Sabourin and (2) d'Ydewalle and Denis were prepared for the World Social Science Report. They illustrate some of the current scope and diversity of the discipline.     

Cross-modal attentional deficits in processing tactile stimulation

In order to substantiate recent theorization on the possible links between the causes of the attentional blink and the psychological refractory period phenomena (e.g., Jolicoeur, 1999a), four experiments are reported in which two target stimuli, T₁ and T₂, were presented in different modalities at varying stimulus onset asynchronies (SOAs), with each stimulus being associated with a distinct task, Task₁ and Task₂. In Experiment 1, T₁ was a tone, and Task₁ was a speeded vocal response based on pitch. T₂ was a brief press applied to either of two distal fingerpads, and Task₂ was a speeded manual response based on tactile stimulus location. In Experiment 2, the same T₁ as that used in Experiment 1 was presented, and in Task₁ the subject either made a speeded vocal response based on pitch or ignored T₁. T₂ was a masked tactile stimulation, and Task₂ was an unspeeded manual discrimination of the tactile stimulation location. This Task₂ was maintained in Experiments 3 and 4. The auditory T₁ was replaced with a white digit embedded in a rapid serial visualization presentation of a stream of black letters, and in Task₁ the subject either made an unspeeded decision based on T₁ identity or ignored T₁. In all the experiments, the results showed an SOA-locked impairment in Task₂. As SOA was decreased, reaction times in the speeded Task₂ of Experiment 1 increased, and accuracy in the unspeeded Task₂ of Experiments 2–4 decreased. The SOA-locked impairment was almost eliminated when T₁ could be ignored or was absent. The results are discussed in terms of central processing limitations as the cause of such effects.