Experimental context modulates warning signal effects

Abstract

Previous studies have shown that saccadic eye responses but not manual responses were sensitive to the kind of warning signal used, with visual onsets producing longer saccadic latencies compared to visual offsets. The aim of the present study was to determine the effects of distinct warning signals on manual latencies and to test the premise that the onset interference, in fact, does not occur for manual responses. A second objective was to determine if the magnitude of the warning effects could be modulated by contextual procedures. Three experimental conditions based on the kind of warning signal used (visual onset, visual offset and auditory warning) were run in two different contexts (blocked and non-blocked). Eighteen participants were asked to respond to the imperative stimulus that would occur some milliseconds (0, 250, 500 or 750 ms) after the warning signal. The experiment consisted in three experimental sessions of 240 trials, where all the variables were counterbalanced. The data showed that visual onsets produced longer manual latencies than visual offsets in the nonblocked context (275 vs 261 ms; P < 0.001). This interference was obtained, however, only for short intervals between the warning and the stimulus, and was abolished when the blocked context was used (256 vs 255 ms; P = 0.789). These results are discussed in terms of bottom-up and top-down interactions, mainly those related to the role of attentional processing in canceling out competitive interactions and suppressive influences of a distractor on the relevant stimulus. Key wordsThere has been general agreement that reaction times are reduced when a warning signal (WS) precedes the onset of a subsequent stimulus -the imperative stimulus (IS) -to which a response must be given. Nevertheless, some studies have shown that the facilitation induced by the WS can be modulated by the kind of WS employed; for example, visual onset, visual offset or auditory warning. In two classical papers, Ross and Ross (1,2) showed that visual onset and visual offset used as WS produced different effects on saccade latency: saccadic reaction times obtained after visual offset were shorter

Looking for the GAP effect in manual responses and the role of contextual influences in reaction time experiments

“…Examples of such contextual influences are found in experiments that employ a "blocked" (maintaining conditions or variables constant within a block of trials) or "non-blocked" (randomizing conditions or variables within a block of trials) organization. We have recently found that visual onset and visual offset used as WS produced different effects on manual latencies, and more important, those influences were modulated by the experimental context (blocked vs non-blocked) adopted (15). Since the visual offset represents the critical condition for any study related to the GAP effect, our results suggest that the facilitation induced by the visual offset -the GAP effect, could also be modulated by changes in the experimental context.…”

Influência da atenção temporal em tarefas de discriminação visual e auditiva

“…No caso dos estímulos visuais, uma via dorsal, que inclui as áreas V2 (bandas largas), V3 e V5 e atinge o córtex parietal posterior, está envolvida com a codificação das características espaciais, enquanto que uma via ventral, que inclui as áreas V2 (bandas finas e regiões entre bandas) e V4 e atinge o córtex temporal inferior, está envolvida com a codificação das características não-espaciais do E2 visual (Haxby et al, 1991;Mishkin et al, 1983). -Pinheiro et al, 2004).…”

“…Os indivíduos são capazes de prever a duração da AIE e se preparar temporalmente para o momento de chegada do E2 devido às expectativas temporais automáticas (Nobre et al, 2007). Com a redução da incerteza sobre o momento de ocorrência deste evento, o desempenho é otimizado (Bausenhart et al, 2008;Machado-Pinheiro et al, 2004;Müller-Gethmann, Ulrich, & Rinkenauer, 2003;Rolke & Hofmann, 2007). Por conseqüência, a variabilidade temporal e a incerteza entre os eventos são menores do que nas tarefas que empregam AIE randomizadas (Niemi & Näätänen, 1981).…”

“…Informações sobre intervalos de tempo permitiriam estimar o período que precede o surgimento do evento significativo (Niemi & Näätänen, 1981). Além disso, a facilitação do E1 sobre o TR poderia diferir de acordo como a AIE é manipulada num bloco de tentativas (Machado-Pinheiro, Faria Jr., Gawryszewski, & Ribeiro do Valle, 2004).…”

“…Pinheiro et al, 2004). Esperávamos efeitos atencionais progressivamente maiores da AIE de 50 ms à AIE de 400 ms, uma vez que a interação competitiva entre estímulos de modalidades sensoriais diferentes seria menor.…”