Giovanni Galfano

Inhibition of return in microsaccades

Inhibition of return (IOR) is the term used to describe the phenomenon whereby stimuli appearing at recently attended locations are reacted to less efficiently than stimuli appearing at locations that have not yet been attended. In the present study, we employed a typical IOR paradigm with peripheral uninformative cues while participants maintained their eyes at fixation. Eye position was monitored at a high sampling rate (500xa0Hz) in order to detect miniature eye movements called microsaccades, which have been shown to be crucial for avoiding disappearance of visual image. However, recent studies have demonstrated a close relationship between covert endogenous attentional shifts and the direction of microsaccades. Here, we demonstrate that the direction of microsaccades can be biased away from the peripheral location occupied by a salient, although task-irrelevant, visual signal. Because microsaccades are known not to be under conscious control, our results suggest strong links between IOR and unconscious oculomotor programming.

Space-independent modality-driven attentional capture in auditory, tactile and visual systems

Extending previous evidence for attentional shifts across auditory and visual modalities without the confound of the two modalities originating at different locations (Turatto et al. 2002), we investigated attention shifts between auditory and tactile modalities, and between tactile and visual modalities. Two stimuli (S1 and S2), either in the same or in different modalities, were delivered from the same spatial source and were separated by a variable temporal gap. S1 was task irrelevant, whereas S2 required a speeded discrimination. Results showed that modality switching is detrimental independently of the stimulated modality as long as the temporal lag between S1 and S2 is short enough that there is not time to switch attention before S2 is delivered. We observed automatic, modality-driven, attentional capture, with ipsimodal trials leading to faster response times than crossmodal trials. The present results cannot be accounted for by spatial artifacts, response priming or criterion shifts, and are interpreted as the consequence of a space-independent attentional shift across sensory modalities.

Electrophysiological correlates of stimulus-driven multiplication facts retrieval

We investigated ERPs elicited by stimulus-driven retrieval of arithmetic facts related to multiplication. To this purpose, we recorded the electrophysiological activity from the scalp of participants while they were performing a number-matching task. Crucially, arithmetic was task-irrelevant within this paradigm, because participants were simply to physically compare a cue composed of two one- or two-digit numbers and a single probe number. In line with past literature, behavioral data showed that, in non-matching trials, participants were significantly slower and/or less accurate to respond when the probe number was the product of the two numbers in the cue compared to when the probe number was arithmetically unrelated (i.e., neutral) to those numbers (interference effect). Consistent with recent findings on ERPs and task-relevant arithmetic facts retrieval, we showed that the interference effect resulted in a modulation of the amplitude of an N400-like ERP component, with neutral probes generating relatively more negativity than product probes. The observed dissociation between behavioral data and ERP measures is interpreted as evidence of activation spreading in the lexicon of arithmetic facts, because alternative accounts that rely on strategic factors such as expectancy or semantic matching would have predicted the two measures to show a converging trend.

Stimulus‐driven attentional capture: An empirical comparison of display‐size and distance methods

Four experiments examined attentional capture by colour as assessed by two different investigative methods. Subjects performed a visual search task for a vertical-target line embedded among tilted-distractor lines, presented inside 4, 8, or 12 coloured discs. Interestingly, when the colour singleton was task irrelevant, and data were analysed by means of the display-size method combined with the zero-slope criterion, no evidence for attentional capture by colour was found. However, when data were analysed by means of the distance method, which consists of monitoring the spatial relationship between the target and the singleton, results showed that the target was found faster and/or more accurately when it was inside the singleton than when it was in a nonsingleton location. This provided evidence for a stimulus-driven attentional capture. In addition, the application of signal detection methodology showed that attentional capture, as revealed by the distance method, resulted from a perceptual modulation at the singleton location, rather than from a criterion shift. We conclude that, at least with the kind of stimuli used here, the display-size method combined with the zero-slope criterion is less than ideal for investigating how static discontinuities can affect the automatic deployment of visual attention.

Capacity and contextual constraints on product activation: evidence from task-irrelevant fact retrieval.

Three experiments tested the limiting conditions of multiplication facts retrieval in a number-matching task (LeFevre, Bisanz, & Mrkonjic, 1988). By presenting two digits as cue and by requiring participants to decide whether a subsequent numerical target had been present in the pair, we found interference when the target coincided with the product of the cue digits. This was evidence for obligatory activation of multiplication facts. Also, we showed that multiplication facts retrieval occurred even in the absence of any arithmetic context (i.e., a multiplication sign between the cue digits) and did not require processing resources (i.e., the process met the capacity criterion of automaticity; Jonides, 1981), whereas manipulation of the spatial relation between the two operands (cue digits) negatively affected retrieval. The present work appears to be unique in the context of previous similar studies on mental calculation, which invariably adopted an arithmetic task as the primary demand. We identify this difference as the reason for the failure of all previous studies in revealing independence of multiplication facts from attentional resources. Furthermore, we suggest the application of a contextual definition of automaticity to this kind of retrieval, given the fact that it might depend both on association strength and on contextual setting variables.