Age-related differences and complexity of ongoing activities in time- and event-based prospective memory.

Aging is presumed to disrupt self-initiated processing, and a time-based prospective memory task (i.e., action to be performed at a particular time) entails more self-initiated activities than an event-based prospective memory task (i.e., action to be performed to a critical event). Accordingly, older participants are predicted to be particularly bad in a time-based prospective memory task. However, the prediction is not always confirmed. Self-initiated activities entail central executive functioning. We therefore predicted the age deficit to emerge more clearly when the performance on the ongoing task also involved more central executive functioning. Time-based prospective memory among older adults collapsed when the complexity of the ongoing task increased. However, an age deficit was also obtained when the pacing of the event-based prospective memory task was high because of the general slowing of functioning by older adults.

Revisiting scene primes for object locations.

Sanocki and Epstein (1997) provided evidence that an immediate prior experience of a scene, as a prime, can induce representations of its spatial layout, facilitating the subsequent spatial processing of objects in the target scene. In their experiments, observers responded to target scenes by indicating which of two critical objects was closer in the pictorial space. Reaction times to target scenes that were preceded by same-scene primes without the critical objects were faster than reaction times to target scenes that were preceded by different scene or control primes (geometrical figures). By manipulating the nature of the prime and the interval between prime and target, and by cueing the position of the critical objects, we obtain evidence that the facilitating effect of the same-scene primes can also be explained by the sudden appearance of the critical objects in the target scene. In same-scene conditions, the critical objects cause a local onset, whereas in different-scene and control conditions the entire target scene causes a global onset. As a result, the local onset in the same-scene condition produces a shift of attention towards the critical objects, resulting in faster processing of the critical objects.

The language of uncertainty in genetic risk communication: framing and verbal versus numerical information.

Within a group of 300 medical students, two characteristics of risk communication in the context of a decision regarding prenatal diagnosis for cystic fibrosis are manipulated: verbal versus numerical probabilities and the negative versus positive framing of the problem (having a child with versus without cystic fibrosis). Independently of the manipulations, most students were in favor of prenatal diagnosis. The effect of framing was only significant in the conditions with verbal information: negative framing produced a stronger choice in favor of prenatal diagnosis than positive framing. The framing effect in the verbal conditions and its absence in the numerical conditions are explained by the dominance of the problem-occurrence orientation in health matters as well as a recoding process which is more likely to occur in the numerical (the probability "1-P" switches to its counterpart "P") than in the verbal conditions. The implications for the practice of genetic counseling are discussed.

The influence of semantic context on initial eye landing sites in words.

To determine the role of ongoing processing on eye guidance in reading, two studies examined the effects of semantic context on the eyes' initial landing position in words of different levels of processing difficulty. Results from both studies clearly indicate a shift of the initial fixation location towards the end of the words for words that can be predicted from a prior semantic context. However, shifts occur only in high-frequency words and with prior fixations close to the beginning of the target word. These results suggest that ongoing perceptual and linguistic processes can affect the decision of where to send the eyes next in reading. They are explained in terms of the easiness of processing associated with the target words when located in parafoveal vision. It is concluded that two critical factors might help observing effects of linguistic variables on initial landing sites, namely, the frequency of the target word and the position where the eyes are launched from as regards to the beginning of the target word. Results also provide evidence for an early locus of semantic context effects in reading.

Prospective remembering of Korsakoffs and alcoholics as a function of the prospective-memory and on-going tasks.

Prospective memory is assumed to rely more on the frontal lobes than retrospective memory. Since Korsakoff patients are known to suffer from a general cerebral atrophy and a frontal lobe atrophy in particular, they are expected to show considerably impaired prospective memory. In Experiment 1, the performance of Korsakoff patients on a semantic prospective-memory task (which was embedded in a perceptual on-going task) was particularly bad in Session 1; in Session 2, the Korsakoff patients improved substantially, to reach the performance level of nonamnesic alcoholics. In Experiment 2, prospective memory of the Korsakoff patients and nonamnesic alcoholics was better when the on-going task was more similar to the prospective-memory task; particularly striking was the much better prospective memory in the semantic prospective-memory task when the on-going task requires a semantic analysis than when the on-going task requires perceptual processing. The findings are in agreement with a task-appropriate processing explanation but also in partial agreement with the attention hypothesis of the instance theory of automaticity. Contrary to the frontal lobe hypothesis, prospective memory of the Korsakoff patients was surprisingly good in several aspects of the two experiments.

Eye movement control during reading: foveal load and parafoveal processing.

We tested theories of eye movement control in reading by looking at parafoveal processing. According to attention-processing theories, attention shifts towards word n + 1 only when processing of the fixated word n is finished, so that attended parafoveal processing does not start until the programming of the saccade programming to word n + 1 is initiated (Henderson & Ferreira, 1990; Morrison, 1984), or even later when the processing of word n takes too long (Henderson & Ferreira, 1990). Parafoveal preview benefit should be constant whatever the foveal processing load (Morrison, 1984), or should decrease when processing word n outlasts an eye movement programming deadline (Henderson & Ferreira, 1990). By manipulating the frequency and length of the foveal word n and the visibility of the parafoveal word n + 1, we replicated the finding that the parafoveal preview benefit is smaller with a low-frequency word in foveal vision. Detailed analyses, however, showed that the eye movement programming deadline hypothesis could not account for this finding which was due not to cases where the low-frequency words n had received a long fixation, but to cases of a short fixations less than 240 msec. In addition, there was a spill-over effect of word n to word n + 1, and there was an element of parallel processing of both words. The results are more in line with parallel processing limited by the extent to which the parafoveal word processing on fixation n can be combined with the foveal word processing on fixation n + 1.

Brief foveal masking during scene perception.

In the present experiment, participants were exploring line drawings of scenes in the context of an object-decision task, while eye-contingent display changes manipulated the appearance of the foveal part of the image. Foveal information was replaced by an ovoid noise mask for 83 ms, after a preset delay of 15, 35, 60, or 85 ms following the onset of fixations. In control conditions, a red ellipse appeared for 83 ms, centered around the fixation position, after the same delays as in the noise-mask conditions. It was found that scene exploration was hampered especially when foveal masking occurred early during fixations, replicating earlier findings. Furthermore, fixation durations were shown to increase linearly as the mask delay decreased, which validates the fixation duration as a measure of perceptual processing speed.

Age and interhemispheric transfer time: a failure to replicate.

In a recent study with the Poffenberger paradigm, Brizzolara et al. reported longer estimates of interhemispheric transfer time (IHTT) for children aged 7 years than for adults. They interpreted this finding as evidence for incomplete functional maturity of the corpus callosum in young children. The present study was we were unable to replicate the age effect reported by Brizzolara et al. A closer look at the original study revealed that only 80 observations per child had been collected, which makes it probable that the larger IHTTs in 7-year-olds were caused by stimulus-response compatibility rather than by the lower efficiency of the corpus callosum during childhood years.

Global orientation disrupts the detection of a similar local orientation.

Two experiments were carried out with organised displays in order to examine the role of similarity between global and local orientation in visual search. In both experiments, distractors were organised to form a diagonal line of plus or minus 45 degrees. In experiment 1, target displays were presented tachistoscopically. Participants searched for a target letter 'Q' among distractor letters 'O'. In experiment 2, participants performed a heterogeneity task with target line segments that could have an orientation of either plus or minus 45 degrees. The target appeared partly or completely inside a distractor circle. In both experiments, the target was more difficult to detect when the critical feature aligned with the slope of the global diagonal than when the feature did not align. Taken together, the two experiments suggested a sequential global-to-local processing in which the orientation of the global figure disrupts the detection of a similar local orientation.

A comparison of implicit memory tasks in Korsakoff and alcoholic patients.

Korsakoff patients generally perform at a normal level on implicit memory tasks in contrast to explicit memory tasks. While this difference is sometimes explained in terms of different memory systems underlying the tasks, the different roles of perceptual and conceptual/semantic processes in these tasks have also been emphasized: explicit tasks require mainly conceptual/ semantic processes and implicit tasks are based principally on perceptual processes. However, it has been suggested recently that conceptual/semantic processes may also be involved in some implicit memory tasks (e.g. a Free Association task). Therefore, the performance of Korsakoff and alcoholic patients is here compared in three implicit memory tasks (Stem Completion, Word Identification and Free Association) and one explicit memory task (Cued Recall), allowing us to disentangle what really matters: the nature of the task (implicit or explicit), or the underlying processes (perceptual or conceptual/semantic). The results show only semantic priming in the Free Association and Cued Recall tasks of the alcoholic patients, suggesting that Korsakoff patients have problems particularly with conceptually-driven processing. The implicit or explicit nature of the memory task is not critical.

Mental models and temporal reasoning.

We report five experiments investigating reasoning based on temporal relations, such as: "John takes a shower before he drinks coffee". How individuals make temporal inferences has not been studied hitherto, but we conjectured that they construct mental models of events, and we developed a computer program that reasons in this way. As the program shows, a problem of the form: a before b b before c d while b e while c What is the relation between d and e? where a, b, c, etc. refer to everyday events, calls for just one model, whereas a problem in which the second premise is modified to c before b calls for multiple models because a may occur before c, after c, or at the same time as c. Experiments 1-3 showed that problems requiring one mental model elicited more correct responses than problems requiring multiple models, which in turn elicited more correct answers than multiple model problems with no valid answers. Experiment 4 contrasted the predictions of the model theory with those based on formal rules of inference; its results corroborated the model theory. Experiment 5 confirmed that a premise leading to multiple models took longer to read than the corresponding premise in one-model problems, and that latency to respond correctly was greater for multiple-model problems than for one-model problems. We conclude that the experiments corroborate the mental model theory.

Must reasoning.

The mental model theory of reasoning postulates that individuals reason by constructing models of the situations described by the premises, but the number of explicit models and the information in them is kept to a minimum. The initial models of modal conditionals don't only represent the situations, but they also comment these situations, in terms of permissible and impermissible. The present paper reports three experiments which test the prediction of the mental model theory that a modus tollens inference is easier with a rule that contains the auxiliary verb 'must'. Unlike a normal rule, there is no need to flesh out the models explicitly with a rule containing 'must'. Overall, the results corroborate the prediction of the mental model theory.

Presaccadic attention allocation and express saccades.

Express saccades are visually-guided saccades that are characterized by an extremely short latency of about 100 ms. The present experiments tested the hypothesis that a disengagement of visual attention is necessary for the generation of express saccades. All subjects produced large numbers of express saccades in the gap paradigm, in which the fixation stimulus is removed 200 ms before target onset (Exp. 1), but not in the overlap paradigm, in which the fixation stimulus remained on during the entire trial (Exp. 2). By means of peripheral cues (Exps. 3-5) and central cues (Exps. 6-7), visual attention was directed at the target location for the saccade before the actual appearance of the saccade target. In all experiments, the location cues facilitated rather than abolished express saccades. The generation of express saccades was facilitated even when the currently fixated visual stimulus was not removed before target onset (fixation-overlap; Exps. 5-7). The results are explained by the hypothesis that a disengagement of a separate fixation system is necessary for the generation of express saccades, a hypothesis that is in line with current neurobiological findings.

Comparing color-word and picture-word Stroop-like effects: a test of the Glaser and Glaser (1989) model.

Glaser and Glaser (1989) assume that the processing of colors and pictures is highly similar in that, compared to words, both kinds of stimulis have privileged access to semantic information. This assumption was tested in the present research. In Experiment 1, the season corresponding to the color or to the word of color-word Stroop stimuli had to be named (e.g., green for spring). In Experiment 2, subjects had to name the season corresponding to the picture or the word of a picture-word stimulus (e.g., flower for spring). According to Glaser and Glaser (1989), privileged semantic processing of colors and pictures should be evidenced by a larger interfering power of color and picture distractors than of word distractors. However, the asymmetric pattern of interference was observed only with picture-word stimuli (Experiment 2), but not with color-word stimuli (Experiment 1), suggesting that, unlike pictures, colors do not have privileged access to semantic information. It was also found that word distractors interfered with the semantic processing of pictures, a result that is incompatible with the dominance rule postulated by Glaser and Glaser (1989). From these results, an adapted version of the Glaser and Glaser model is proposed: colors are assumed to have privileged access to a separate color-processing system and the pattern of interference depends upon the relative activation strength of the response alternatives activated by the target and the distractor.

Local and global contextual constraints on the identification of objects in scenes.

Objects likely to appear in a given real-world scene are frequently found to be easier to recognize. Two different sources of contextual information have been proposed as the basis for this effect: global scene background and individual companion objects. The present paper examines the relative importance of these two elements in explaining the context-sensitivity of object identification in full scenes. Specific sequences of object fixations were elicited during free scene exploration, while fixation times on designated target objects were recorded as a measure of ease of target identification. Episodic consistency between the target, the global scene background, and the object fixated just prior to the target (the prime), were manipulated orthogonally. Target fixation times were examined for effects of prime and background. Analyses show effects of both factors, which are modulated by the chronology and spatial extent of scene exploration. The results are discussed in terms of their implications for a model of visual object recognition in the context of real-world scenes.

Effects of multiple reference points in spatial stimulus-response compatibility.

In two experiments, spatial stimulus-response compatibility effects in situations where the stimulus could appear in eight different locations were investigated. The locations were obtained as a result of orthogonal manipulation of hemispace, visual hemifield within hemispace, and relative position within hemifield. In the first experiment, only relative position within hemifield was relevant for selecting one of two responses (left or right). The results showed that both hemifield and relative position formed the basis of compatibility effects. In the second experiment, which was in most respects identical to the first, all spatial information was irrelevant. Only the geometrical shape of the stimulus determined the correct response. The results showed three S-R compatibility effects, based on hemispace, hemifield, and relative position. These results contradict earlier findings, and have implications for models of stimulus-response compatibility.

Detection of symmetry in tachistoscopically presented dot patterns: effects of multiple axes and skewing.

We examined the effects of multiple axes and skewing on the detectability of symmetry in tachistoscopically presented (100-msec) dot patterns to test the role of normal grouping processes based on higher order regularities in element positions. In addition to the first-order regularities of orientational uniformity and midpoint collinearity (Jenkins, 1983), bilateral symmetry (BS) gives rise to second-order relations between two pairs of symmetric elements (represented by correlation quadrangles). We suggest that they allow the regularity (i.e., BS) to emerge simply as a result of the position-based grouping that takes place normally, so that no special symmetry-detection mechanism has to be postulated. In combination with previously investigated variables--number and orientation of axes--we introduced skewing (resulting from orthographic projection of BS) to manipulate the kind and number of higher order regularities. In agreement with our predictions, the data show that the effect of skewing angle (varied at three 15 degrees steps, clockwise and counterclockwise) on the preattentive detectability of symmetry (measured with d') increases as the number of axes decreases. On the basis of some more specific findings, we suggest that it is not as much the number of correlation quadrangles that determines the saliency of a regularity as it is the degree to which they facilitate or "bootstrap" each other.

Hemisphere-specific resource demands of task expectancies.

The hemisphere-specific resource demands of expecting letter- and figure-matching tasks were investigated, using dual-task methodology. Matching task expectancies were induced by blocking trials with respect to stimulus type (letters or geometrical figures). On one third of the trials, the matching stimuli were unexpectedly omitted. The secondary task required a speeded reaction to a laterally presented auditory probe. The side of probe presentation was unpredictable. Probe reaction times were taken as an index of the resource demands imposed by the primary task on the contralateral hemisphere. For both the trials with and without matching stimuli, probe reaction times showed a significant interaction between lateral side of probe presentation and block type (letters or figures). When letters were expected, reaction times were slower in the left-hemisphere probe task. Probe reaction times were equally fast for both sides when figures were expected. Overall, these results indicate that task expectancies primarily demand resources from the hemisphere that is specialized for carrying out the expected task.

Tachistoscopic presentation of verbal stimuli for assessing cerebral dominance: reliability data and some practical recommendations.

Reliability data point to rather high test-retest correlations (greater than or equal to 0.65) for VHF data with four- and five-letter words as stimuli, but replicate previous findings that the first test score correlates poorly with later test scores. The same results are obtained for accuracy and latency data, though small differences exist. All laterality indices lead to the same conclusions and have high intercorrelations. The point-biserial correlation coefficient is, however, a slightly more reliable index of naming latency than the mere difference between LVF and RVF. No such superiority is found for the indices based on accuracy data. The results also point to the need to present a sufficient number of stimuli before firm conclusions can be drawn.