Géry d'Ydewalle

Perceptual effects of scene context on object identification.

SummaryIn a number of studies the context provided by a real-world scene has been claimed to have a mandatory, perceptual effect on the identification of individual objects in such a scene. This claim has provided a basis for challenging widely accepted data-driven models of visual perception in order to advocate alternative models with an outspoken top-down character. The present paper offers a review of the evidence to demonstrate that the observed scene-context effects may be the product of post-perceptual and task-dependent guessing strategies. A new research paradigm providing an on-line measure of genuine perceptual effects of context on object identification is proposed. First-fixation durations for objects incidentally fixated during the free exploration of real-world scenes are shown to increase when the objects are improbable in the scene or violate certain aspects of their typical spatial appearance in it. These effects of contextual violations are shown to emerge only at later stages of scene exploration, contrary to the notion of schema-driven scene perception effective from the very first scene fixation. In addition, evidence is reported in support of the existence of a facilitatory component in scene-context effects. This is taken to indicate that the context directly affects the ease of perceptual object processing and does not merely serve as a framework for checking the plausibility of the output of perceptual processes. Finally, our findings are situated against other contrasting results. Some future research questions are highlighted.

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.

Watching Subtitled Television Automatic Reading Behavior

When foreign movies are subtitled in the local language, reading subtitles is more or less obligatory. Our previous studies have shown that knowledge of the foreign language or switching off the sound track does not affect the total time spent in the subtitled area. Long-standing familiarity with subtitled movies and processing efficiency have been suggested as explanations. Their effects were tested by comparing American and Dutch-speaking subjects who differ in terms of subtitling familiarity. In Experiment 1, American subjects watched an American movie with English subtitles. Despite their lack of familiarity with subtitles, they spent considerable time in the subtitled area. Accordingly, subtitle reading cannot be due to habit formation from long-term experience. In Experiment 2, a movie in Dutch with Dutch subtitles was shown to Dutch-speaking subjects. They also looked extensively at the subtitles, suggesting that reading subtitles is preferred because of efficiency in following and understanding the movie. However, the same findings can also be explained by the more dominant processing of the visual modality. The proportion of time spent reading subtitles is consistently larger with two-line subtitles than with one-line subtitles. Two explanations are provided for the differences in watching one- and two-line subtitles: (a) the length expectation effect on switching attention between picture and text and (b) the presence of lateral interference within two lines of text.

Incidental foreign-language acquisition by children watching subtitled television programs.

Previous research on adults has demonstrated incidental foreign-language acquisition by watching subtitled television programs in a foreign language. Based on these findings and the literature about the sensitive period for language acquisition, we expected the acquisition to be larger with children. A short subtitled cartoon was presented to Dutch-speaking children (8–12 years old). We varied the channel in which the foreign and native languages were presented (sound track and subtitles); we also looked at the effects of the existing knowledge of the foreign language (due to formal teaching at school) and the linguistic similarity between the native and the foreign language (using Danish and French as foreign languages). We obtained real but limited foreign-language acquisition and in contrast to the sensitive language-acquisition hypothesis, the learning of the children was not superior to that of adults investigated in prior studies. The acquisition here does not profit from the more formal language learning at school. Contrary to the adults, the children tend to acquire more when the foreign language is in the sound track than in the subtitles.

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.

Working memory and everyday conditional reasoning: Retrieval and inhibition of stored counterexamples

Two experiments examined the contribution of working memory (WM) to the retrieval and inhibition of background knowledge about counterexamples (alternatives and disablers, Cummins, 1995) during conditional reasoning. Experiment 1 presented a conditional reasoning task with everyday, causal conditionals to a group of people with high and low WM spans. High spans rejected the logically invalid AC and DA inferences to a greater extent than low spans, whereas low spans accepted the logically valid MP and MT inferences less frequently than high spans. In Experiment 2, an executive-attention-demanding secondary task was imposed during the reasoning task. Findings corroborate that WM resources are used for retrieval of stored counterexamples and that people with high WM spans will use WM resources to inhibit the counterexample activation when the type of counterexample conflicts with the logical validity of the reasoning problem.

A dual-process specification of causal conditional reasoning

There are two accounts describing causal conditional reasoning: the probabilistic and the mental models account. According to the probabilistic account, the tendency to accept a conclusion is related to the probability by which cause and effect covary. According to the mental models account, the tendency to accept a conclusion relates to the availability of counterexamples. These two accounts are brought together in a dual-process theory: It is argued that the probabilistic reasoning process can be considered as a heuristic process whereas the mental models account can be seen as its analytic counterpart. Experiment 1 showed that the two processes differ on a temporal dimension: The variation in fast responses was best predicted by the variation in likelihood information, while the variation in slow responses was best predicted by variation in counterexample information. Experiments 2 and 3 validate the override principle: The likelihood conclusion can be overwritten when specific counterexamples are retrieved in time. In Experiment 2 both accounts were compared based on their difference in input. In Experiment 3 we used a verbal protocol analysis to validate the dual-process idea at the output level. The data of the three experiments provide converging support for framing the two reasoning accounts in a dual-process theory.

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.

Orientational effects and component processes in symmetry detection

In previous research on symmetry detection, factors contributing to orientational effects (axis and virtual lines connecting symmetrically positioned dots) and component processes (axis selection and pointwise evaluation) have always been confounded. The reason is the restriction to bilateral symmetry (BS), with pointwise correspondences being orthogonal to the axis of symmetry. In our experiments, subjects had to discriminate random dot patterns from symmetries defined by combining 12 axis orientations (every 15°) with seven reflection angles (0°, yielding BS, and three clockwise and counterclockwise 15° steps, yielding skewed symmetry, SS). In Experiment 1, with completely randomized trial order, a significant interaction between axis and skewing angle was obtained, indicating that classically observed orientational effects are restricted to BS and that the orientation of the pointwise correspondences is important. These basic findings were replicated in three subsequent experiments, which differed in that they used blocks containing patterns with the same axis (Experiment 2), virtual lines orientation (Experiment 3), or their combination (Experiment 4). Based on a comparison between the results obtained by these manipulations, we suggest a possible reason for the failure of preattentive symmetry detection in the case of dot patterns with SS.

Eye Movements of Children and Adults While Reading Television Subtitles

Abstract. Eye movements of children (Grade 5-6) and adults were monitored while they were watching a foreign language movie with either standard (foreign language soundtrack and native language sub...