Developmental time course of the acquisition of sequential egocentric and allocentric navigation strategies

Navigation in a complex environment can rely on the use of different spatial strategies. We have focused on the employment of “allocentric” (i.e., encoding interrelationships among environmental cues, movements, and the location of the goal) and “sequential egocentric” (i.e., sequences of body turns associated with specific choice points) strategies during navigation. To investigate the developmental pattern of these two strategies in school-aged children, we used a virtual reality paradigm in which the spontaneous or imposed use of both strategies could be assessed. Our results showed an increase in spontaneous use of the allocentric strategy and also an increase in reliance on environmental landmarks with age. Although a majority of the children spontaneously used the sequential egocentric strategy, all age groups performed above chance when the allocentric strategy was imposed. Altogether, our findings suggest that young children are able to employ an allocentric strategy but that the nature of this allocentric strategy changes progressively in a complex cognitive representation between 5 and 10 years of age.     

Catastrophe theory and its critics

Catastrophe theory has been sharply criticized because it does not seem to have practical applications nor does it seem to allow us to increase our power over Nature. I want to rehabilitate the theory by foregoing the controversy raised by scientists about its practical efficiency. After a short exposition of the theory's mathematical formalism and a detailed analysis of the main objections that have been raised against it, I argue that theory is not only to be judged on its practical results, which are in fact limited, but also on its epistemological and philosophical implications. Catastrophe theory indeed represents a real revolution in science: it announces the coming of a more theoretical, less practical, science, having more to do with understanding reality than with acting on it, and, from that point of view, it may be considered as the modern philosophy of Nature.     

Positive and negative instructions in symbolic paired comparisons with the months of the year

Summary We investigated the semantic interpretation of positive (MORE THAN) and negative (LESS THAN) instructions in a symbolic paired comparison task with an overlearned and finite series of stimuli. French-speaking subjects were asked to indicate which member of month pairs occurred PLUS TOT (earlier), PLUS TARD (later), MOINS TOT (less early), or MOINS TARD (less late) in the year. In Experiment 1, the sign of the comparative instruction (MORE vs. LESS) was kept constant, while its attribute (EARLY vs. LATE) varied. In Experiment 2, the attribute of the instruction was kept constant, while its sign varied. The main results indicate that (1) negative instructions (with adverb LESS) yielded longer response latencies than positive ones (with adverb MORE); this difference was particularly salient on the first experimental session but, on subsequent sessions, it was reduced in Experiment 1 and neutralized in Experiment 2; (2) a symbolic-distance effect was observed on response latency and response accuracy with the four forms of the comparative instruction; (3) violations of monotonicity were noted in the symbolic-distance effect when June was used as a reference month in the analysis; (4) the serial-position effect had the form of a double-bowed curve with three stable anchor points around January, June, and December; and (5) the pattern of semantic-congruity effect with negative instructions was the exact reversal of that obtained with positive instructions; that is, if the month pairs occurred early in the year, response latencies were shorter with the instruction less late than with less early, whereas if the month pairs occurred late in the year response latencies were shorter with instruction "less early than with less late. The theoretical implications of these results for Banks' Semantic-coding model and Holyoak's Reference-point model are discussed.     

Eye position affects audio-visual fusion in darkness

We investigated the frame of reference involved in audio-visual (AV) fusion over space. This multisensory phenomenon refers to the perception of unity resulting from visual and auditory stimuli despite their potential spatial disparity. The extent of this illusion depends on the eccentricity in azimuth of the bimodal stimulus (Godfroy et al, 2003 Perception 32 1233-1245). In a previous study, conducted in a luminous environment, Roumes et al 2004 (Perception 33 Supplement, 142) have shown that variation of AV fusion is gaze-dependent. Here we examine the contribution of ego- or allocentric visual cues by conducting the experiment in total darkness. Auditory and visual stimuli were displayed in synchrony with various spatial disparities. Subjects had to judge their unity ('fusion' or 'no fusion'). Results showed that AV fusion in darkness remains gaze-dependent despite the lack of any allocentric cues and confirmed the hypothesis that the reference frame of the bimodal space is neither head-centred nor eye-centred.     

Edge-induced illusory contours and visual detection: Subthreshold summation or spatial cueing?

Findings that illusory contours can facilitate visual detection of a subthreshold real line (Dresp & Bonnet, 1995) were not replicated, when line-induced instead of edge-induced illusory contour stimuli were used (Salvano-Pardieu et al., 2006). Rather, the results of the latter study supported the importance of spatial cues. The present study was designed to investigate whether spatial cueing might also facilitate detection of targets superimposed on edge-induced illusory contours. In Experiment 1, a target line was superimposed on the illusory contour of a Kanizsa square, presented between dots with a precise or distant location to the target, or on a homogeneous field (control). Detection of the target was poorest for the control, followed by the distant-dots and Kanizsa conditions, whereas it was best for precisely cueing dots. Experiment 2 replicated the conditions in Experiment 1 (Kanizsa, precisely cueing dots, and control) with additional controls for possible luminance effects. The two new conditions matched the Kanizsa condition for overall luminance and preciseness of spatial cueing without generating illusory contours. Performance was best in the dot condition and worst in the control, but the same across the Kanizsa and matched luminance conditions. In Experiments 3 and 4, the stimuli presented were matched more closely to those used by Dresp and Bonnet, but still the results confirmed those obtained in our Experiments 1 and 2. Together, these experiments strongly suggest that detection is also facilitated by spatial cueing rather than subthreshold summation, in the case of edge-induced illusory contours.     

Why Did They Claim Too Much? The Role of Causal Attributions in Explaining Level of Cooperation in Commons and Anticommons Dilemmas

The present study ( N  = 200) investigated participants' attributions for explaining the behavior of noncooperative and cooperative targets in a commons and anticommons dilemma. The attribution dimensions of concern for others, fear, (low levels of) greed, and efficiency were highly related and were interpreted to reflect prosocial orientation. Cooperative targets were judged as more prosocial, but these differences were more pronounced in the commons than in the anticommons dilemma. Crossover interaction effects were obtained for ignorance and fear, revealing higher attribution scores for the noncooperative target in the commons dilemma and the cooperative target in the anticommons dilemma. It is argued that commons and anticommons dilemmas constitute different frames of reference for judging cooperative behavior.