EXPRESS: Distraction by auditory novelty during reading: Evidence for disruption in saccade planning, but not saccade execution

Novel or unexpected sounds that deviate from an otherwise repetitive sequence of the same sound cause behavioural distraction. Recent work has suggested that distraction also occurs during reading as fixation durations increased when a deviant sound was presented at the fixation onset of words. The present study tested the hypothesis that this increase in fixation durations occurs due to saccadic inhibition. This was done by manipulating the temporal onset of sounds relative to the fixation onset of words in the text. If novel sounds cause saccadic inhibition, they should be more distracting when presented during the second half of fixations when saccade programming usually takes place. Participants read single sentences and heard a 120 ms sound when they fixated five target words in the sentence. On most occasions (p= 0.9), the same sine wave tone was presented (“standard”), while on the remaining occasions (p= 0.1) a new sound was presented (“novel”). Critically, sounds were played either during the first half of the fixation (0 ms delay) or during the second half of the fixation (120 ms delay). Consistent with the saccadic inhibition hypothesis, novel sounds led to longer fixation durations in the 120 ms compared to the 0 ms delay condition. However, novel sounds did not generally influence the execution of the subsequent saccade. These results suggest that unexpected sounds have a rapid influence on saccade planning, but not saccade execution.

The spread of presaccadic attention depends on the spatial configuration of the visual scene

When preparing a saccade, attentional resources are focused at the saccade target and its immediate vicinity. Here we show that this does not hold true when saccades are prepared toward a recently extinguished target. We obtained detailed maps of orientation sensitivity when participants prepared a saccade toward a target that either remained on the screen or disappeared before the eyes moved. We found that attention was mainly focused on the immediate surround of the visible target and spread to more peripheral locations as a function of the distance from the cue and the delay between the target’s disappearance and the saccade. Interestingly, this spread was not accompanied with a spread of the saccade endpoint. These results suggest that presaccadic attention and saccade programming are two distinct processes that can be dissociated as a function of their interaction with the spatial configuration of the visual scene.

Spatial constraints in saccadic inhibition of return

Despite being one of the most prominent and well-known biases in visual orienting, inhibition of return (IOR), a tendency to avoid recently viewed locations, remains a controversial and poorly understood phenomenon. To investigate the characteristics of IOR, participants made rapid alternating saccades between two targets, return saccades, or produced eye movements that followed an “hourglass” pattern in which the same location was only revisited every fourth eye movement. Saccade dwell times and secondary saccade frequency increased when the eye returned immediately to a previously viewed location. Surprisingly, the higher rate of secondary saccades did not contribute directly to the longer dwell times in the return condition. Saccade precision was equivalent between conditions, but saccade gain was smaller for hourglass saccades. Varying the height and width of the hourglass revealed that the magnitude of inhibition of return depended on the angular separation between subsequent saccades and was not characterized by a constant zone around the targets. Even when the angular difference of hourglass saccades, relative to return saccades, was made as small as 3 degrees, significant differences in dwell times and secondary saccade characteristics were observed. The results further explicate constraints on inhibition of return, reveal novel factors guiding secondary saccade programming, and provide insight into motor and attentional constraints governing the rate of sequential eye movements.

The effect of offset cues on saccade programming and covert attention

Salient peripheral events trigger fast, “exogenous” covert orienting. The influential premotor theory of attention argues that covert orienting of attention depends upon planned but unexecuted eye-movements. One problem with this theory is that salient peripheral events, such as offsets, appear to summon attention when used to measure covert attention (e.g., the Posner cueing task) but appear not to elicit oculomotor preparation in tasks that require overt orienting (e.g., the remote distractor paradigm). Here, we examined the effects of peripheral offsets on covert attention and saccade preparation. Experiment 1 suggested that transient offsets summoned attention in a manual detection task without triggering motor preparation planning in a saccadic localisation task, although there were a high proportion of saccadic capture errors on “no-target” trials, where a cue was presented but no target appeared. In Experiment 2, “no-target” trials were removed. Here, transient offsets produced both attentional facilitation and faster saccadic responses on valid cue trials. A third experiment showed that the permanent disappearance of an object also elicited attentional facilitation and faster saccadic reaction times. These experiments demonstrate that offsets trigger both saccade programming and covert attentional orienting, consistent with the idea that exogenous, covert orienting is tightly coupled with oculomotor activation. The finding that no-go trials attenuates oculomotor priming effects offers a way to reconcile the current findings with previous claims of a dissociation between covert attention and oculomotor control in paradigms that utilise a high proportion of catch trials.

Morphological structure influences the initial landing position in words during reading Finnish

The preferred viewing location in words [Rayner, K. (1979). Eye guidance in reading: Fixation locations within words. Perception, 8, 21–30] during reading is near the word centre. Parafoveal word length information is utilized to guide the eyes toward it. A recent study by Yan and colleagues [Yan, M., Zhou, W., Shu, H., Yusupu, R., Miao, D., Krügel, A., & Kliegl, R. (2014). Eye movements guided by morphological structure: Evidence from the Uighur language. Cognition, 132, 181–215] demonstrated that the word’s morphological structure may also be used in saccadic targeting. The study was conducted in a morphologically rich language, Uighur. The present study aimed at replicating their main findings in another morphologically rich language, Finnish. Similarly to Yan et al., it was found that the initial fixation landed closer to the word beginning for morphologically complex than for monomorphemic words. Word frequency, saccade launch site, and word length were also found to influence the initial landing position. It is concluded that in addition to low-level factors (word length and saccade launch site), also higher level factors related to the word’s morphological structure and frequency may be utilized in saccade programming during reading.

Visual attention is not always spatially coupled to subsequent oculomotor program

The premotor theory of attention postulates that spatial attention arises from the activation of saccade areas and that the deployment of attention is the consequence of motor programming. Yet, attentional and oculomotor processes have been shown to be dissociable at the neuronal level in covert attention tasks. To investigate a potential dissociation at the behavioral level, we instructed human participants to saccade towards one of two nearby, competing saccade cues. The spatial distribution of visual attention was determined using oriented Gabor stimuli presented either at the cue locations, between them or at several other equidistant locations. Results demonstrate that accurate saccades towards one of the cues were associated with presaccadic enhancement of visual sensitivity at the respective saccade endpoint compared to the non-saccaded cue location. In contrast, averaging saccades, landing between the two cues, were not associated with attentional facilitation at the saccade endpoint, ruling out an obligatory coupling of attentional deployment to the oculomotor program. Rather, attention before averaging saccades was equally distributed to the two cued locations. Taken together, our results reveal a spatial dissociation of visual attention and saccade programming. They suggest that the oculomotor program depends on the state of attentional selection before saccade onset, and that saccade averaging arises from unresolved attentional selection.

Music sight-reading expertise, visually disrupted score and eye movements

Previous studies have shown that performance at a defined level of music sight reading for pianists (6th Grade) is predictive of eye movement patterns (Waters, 1998) and that such patterns resemble those of text reading experts (Furneaux & Land, 1999; Sloboda, 1974; Truitt, 1997; Wolf, 1976). However, little is known about how expertise might affect eye movement patterns when the score has been visually disrupted using notational features that are unexpected or outside conventional presentation.The current project examined the effect of altering features of the music score on eye movement patterns of expert and non-expert music sight readers. Participants sight read specifically composed musical excerpts, which were then re-presented with the bar-lines removed, altered inter-note spacing and unpredictable beaming directions. Fixation and saccade characteristics were measured and compared between the two performances. It was expected that expert music sight readers would be most affected when the score was disrupted as they would be less capable of grouping notes into familiar, single units for efficient visual processing. Expert sight readers performed significantly faster than non-experts in both conditions: p<0.0001. Saccadic latency increased significantly for experts in the disrupted condition: p=0.0259, while non-experts increased slightly, not reaching significance. This suggests that the disruption of visual expectation was sufficient to cause a lengthening of saccade programming in the experts - an indication of interference with the chunking process. The resultant EM patterns for the non-experts demonstrated heightened non-expert behaviours: increased fixations of shorter duration.