Cesar Galera

Local and global factors of similarity in visual search

Effects of the similarity between target and distractors in a visual search task were investigated in several experiments. Both familiar (numerals and letters) and unfamiliar (connected figures in a 5 × 5 matrix) stimuli were used. The observer had to report on the presence or absence of a target among a variable number of homogeneous distractors as fast and as accurately as possible. It was found that physical difference had the same clear effect on processing time far familiar and for unfamiliar stimuli: processing time decreased monotonically with increasing physical difference. Distractors unrelated to the target and those related to the target by a simple transformation (180° rotation, horizontal or vertical reflection) were also compared, while the physical difference was kept constant. For familiar stimuli, transformational relatedness increased processing time in comparison with that fort unrelated stimulus pairs. It was further shown in a scaling experiment that this effect could be accounted for by the amount of perceived similarity of the target-distractor pairs. For unfamiliar stimuli, transformational relatedness did have a smaller and less pronounced effect. Various comparable unrelated distractors resulted in a full range of processing times. Results from a similarity scaling experiment correlated well with the outcome of the experiments with unfamiliar stimuli. These results are interpreted in terms of an underlying continuum of perceived similarity as the basis of the speed of visual search, rather than a dichotomy of parallel versus serial processing.

Attentive mechanisms in visual search.

Selective attention can be employed to a restricted region in space or to specific objects. Many properties of this attentional window or spotlight are not well understood. In the present study, we examined the question whether the putative shape of the attentional spotlight can be determined by endogenous cueing within a visual search paradigm. Participants searched for a target among distractors, which were arranged within a vertical or horizontal rectangle. The shape of this rectangle was cued endogenously in a valid or invalid way. Response times (RTs) to correct identification of target orientation were recorded. In Experiment 1, the difference between valid and invalid RTs demonstrated that cueing resulted in elongated attentional areas. This was true only for a group of experienced psychophysical participants, whereas a group of inexperienced participants were not able to use cueing in this way. In Experiment 2, the line motion illusion was used to examine the spatial properties of the attended area. The results confirmed for both experienced and inexperienced participants that attention was confined to the cued elongated area only. We present converging evidence for an attentional spotlight whose shape can be adjusted flexibly by appropriate endogenous cueing.

Memória visuo-espacial a curto prazo: os efeitos da supressão articulatória e de uma tarefa aritmética

We investigated the nature of the information stored in visuo-spatial short-term memory in two experiments. In the first experiment, a spatial localization task was performed simultaneously with articulatory suppression and arithmetical subtraction tasks. The articulatory suppression has a negative effect on the performance with letters, but not with visual patterns. Despite that, the recall of the letters is better than the recall of the visual patterns. This result suggests that the storage of the visual patterns does not use the phonological loop, and that the articulatory suppression, even if it inhibits the use of the phonological loop, cannot inhibit the access to the semantic information. In the second experiment we established the effect of the visual similarity on the capacity of memory for the spatial position. The results confirm the use of visual codes and suggest that the storage capacity of the visual stimuli is limited, but not restricted to the recency items.

Atenção visual: estudos comportamentais da seleção baseada no espaço e no objeto

Apesar de intensamente pesquisados nos ultimos trinta anos, os processos cognitivos relacionados a atencao visual humana ainda apresentam varias lacunas e instigam investigacoes sobre os mecanismos de selecao e integracao da informacao relevante contida no ambiente. Basicamente, os esforcos para a compreensao desta arquitetura cognitiva estao centrados em dois grandes modelos teoricos sobre a atencao visual: um baseado na localizacao espacial ocupada pelos objetos no campo visual e outro baseado nas caracteristicas do objeto a ser atendido. A revisao realizada neste artigo busca sistematizar algumas contribuicoes experimentais importantes a respeito desses modelos bem como evidenciar algumas particularidades da natureza dos processos envolvidos na mobilizacao da atencao visual humana.

Memória de trabalho viso-espacial em crianças de 7 a 12 anos

Visuo-spatial working memory in 7-12 year old children. This study aimed to evaluate the mechanisms of visual-spatial memory in children. Seventy eight children took part in an experiment with four factors: children’s age, stimuli spatial position, stimuli visual similarity, stimuli set color. The results have shown that all main factors are statistically meaningful. The oldest children presented a better performance than the youngest ones. Stimuli set formed by low similarity letters were better recollected than the stimuli set formed by high similarity letters. The recall of the spatial position of letters was better in trials where the letters of a set were presented in the same color. The percentage of correct recall changed meaningfully as a function of the spatial position in which the target had been presented. The results were interpreted according to models that emphasize aspects of development of cognitive strategies along with the human development, especially the working memory model.

Memória visuoespacial e cinestésica de curto prazo em crianças de 7 a 10 anos

We investigated the visuo-spatial and kinesthetic short term memory in children aged between 7 and 10 years through the Corsi Block test. The results showed that performance gets better with age that it is affected by sequence extension and by number of crossings paths. The performance is better in the visual modality than in the kinesthetic one; both modalities are affected in the same way by the sequence extension and number of crossing paths. Serial position curves are marked by primacy effect; recency effect is present just in visual modality. In sequences with six and seven blocks, when considered the number of crossing paths, the performance tends to get better in a higher tax for visual modality than for kinesthetic. The results do not support a kinesthetic memory independent of the spatial system, but suggests that both components contribute to the performance in the Corsi block test.

Selecao e analise de estimulos na tarefa de busca visual

The capacity of processing several cognitive stages simultaneously still generates a considerable disagreement among models that try to understand the processing of visual information. Many experimental results suggest two main possibilities for the information flow between information processing stages: a discrete or a continuous flow. Two experiments have in the present study to investigate were designed attentional processing whether the information at first discarded in a pre-attentive state can influence the of selected information in a visual search task. The results show that the stimuli initially discarded in an automatic process of selection do not interfere in the attention all processing of stimuli in a visual search. The results support the models that predict an early selection of the relevant stimuli and a discrete transmission of the information between the cognitive processing stages.

Quantidade e qualidade: duas abordagens da memória visuo-espacial

Neste texto apresentamos alguns aspectos que tem caracterizado diferentes abordagens no estudo da memoria a curto prazo. O enfoque quantitativo, proposto por Ebbinghaus (1885), aborda a memoria em termos de sua capacidade de armazenamento. A memoria e vista como um armazem no qual a informacao e depositada e posteriormente recuperada; sua capacidade e determinada tanto em termos do numero de itens que consegue armazenar, como em termos da duracao dos itens armazenados. O enfoque qualitativo, com bases na tradicao da Gestalt e no trabalho de Bartlett (1932), aborda a memoria como um processo de representacao ou de reconstrucao de eventos passados. Nesta abordagem a memoria e avaliada em termos da correspondencia entre a representacao e aquilo que e representado.

Componentes funcionais da memória visuoespacial

Research on working memory has been focused on fractionating specialized subsystems responsible for storage of verbal, visuospatial and multimodal information. In the present paper, we review the fractionation of visuospatial working memory into separate visual and spatial components. The availability of visual codes in working memory is supported by the effects of visual similarity and irrelevant information. Spatial memory seems to depend on attention resources and its relationship with visual memory is still controversial

Características atentivas reveladas por dicas múltiplas locais e globais

The characteristics of the attentive focus were investigated through the effect of local and global multiple cues, multiple and unitary, on the performance of a visual search task. The results show a gain in the performance of tests with valid multiple local cues; the gain is proportional to the size of the area in which the stimuli are presented. In the tests with valid local tips for the area there is a gain when the stimuli are presented in the larger area and a cost in the smaller area. Global cues do not generate a gain in tests with valid cues but are followed by a cost in tests with invalid cues. There is also a cost in tests where the attentive focus must be expanded or contracted. The results suggest that the model of multiple attentive focuses is more adequate to explain performance in tests with multiple local cues.