Spatial organisation in passive tactile perception: is there a tactile field?

The perceptual field is a cardinal concept of sensory psychology. 'Field' refers to a representation in which perceptual contents have spatial properties and relations which derive from the spatial properties and relations of corresponding stimuli. It is a matter of debate whether a perceptual field exists in touch analogous to the visual field. To study this issue, we investigated whether tactile stimuli on the palm can be perceived as complex stimulus patterns, according to basic spatial principles. Subjects judged the intensity of a target stimulus to the palm, ignoring two brief preceding touches at nearby flanker locations. We found that the judgements of the target intensity were boosted by flankers when the target lay on the line joining the flankers in comparison to when the target lay away from this line. Therefore, we suggest that a tactile spatial organisation, i.e. a tactile field, exists; the field supports the relation of collinearity; it is automatically and implicitly activated by touch, and it groups spatially coherent perceptual contents.     

Responses to visual,tactile and visual–tactile forward collision warnings while gaze on and off the road

The objective of the current driving simulator study (N = 20) was to assess brake reaction time (BRT) and subjective experiences of visual (V), tactile (T), and visual–tactile (VT) collision warnings when the drivers’ visual orientation was manipulated between four locations (i.e., road and three different mirror locations). V warning was a blinking light in a windscreen, T warning was implemented by a vibrating accelerator pedal, and VT warning was their synchronous combination. The results showed that all the warning stimuli were detected in 100% accuracy in all visual orientations, but T and VT warnings produced significantly faster BRTs when compared to V warning. It was found that BRT to V warning was the slowest while observing the furthermost side mirror. However, BRTs following T and VT warnings remained unaffected by the visual orientations. Both the objective BRT measurements and subjective evaluations indicated a superiority of T and VT warnings against a sole V warning, not only in general terms, but also separately for different visual orientations.     

Do "mudsplashes" induce tactile change blindness?

The phenomenon of change blindness (the surprising inability of people to correctly perceive changes between consecutively presented displays), primarily reported in vision, has recently been shown to occur for positional changes presented in tactile displays as well. Here, we studied people's ability to detect changes in the number of tactile stimuli in successively presented displays composed of one to three stimuli distributed over the body surface. In Experiment 1, a tactile mask consisting of the simultaneous activation of all seven possible tactile stimulators was sometimes presented between the two to-be-discriminated tactile displays. In Experiment 2, a "mudsplash" paradigm was used, with a brief irrelevant tactile distractor presented at the moment of change of the tactile display. Change blindness was demonstrated in both experiments, thus showing that the failure to detect tactile change is not necessarily related to (1) the physical disruption between consecutive events, (2) the effect of masking covering the location of the change, or (3) the erasure or resetting of the information contained within an internal representation of the tactile display. These results are interpreted in terms of a limitation in the number of spatial locations/events that can be consciously accessed at any one time. This limitation appears to constrain change-detection performance, no matter the sensory modality in which the stimuli are presented.     

Do “mudsplashes” induce tactile change blindness?

The phenomenon of change blindness (the surprising inability of people to correctly perceive changes between consecutively presented displays), primarily reported in vision, has recently been shown to occur for positional changes presented in tactile displays as well. Here, we studied people’s ability to detect changes in the number of tactile stimuli in successively presented displays composed of one to three stimuli distributed over the body surface. In Experiment 1, a tactile mask consisting of the simultaneous activation of all seven possible tactile stimulators was sometimes presented between the two to-be-discriminated tactile displays. In Experiment 2, a “mudsplash” paradigm was used, with a brief irrelevant tactile distractor presented at the moment of change of the tactile display. Change blindness was demonstrated in both experiments, thus showing that the failure to detect tactile change is not necessarily related to (1) the physical disruption between consecutive events, (2) the effect of masking covering the location of the change, or (3) the erasure or resetting of the information contained within an internal representation of the tactile display. These results are interpreted in terms of a limitation in the number of spatial locations/events that can be consciously accessed at any one time. This limitation appears to constrain change-detection performance, no matter the sensory modality in which the stimuli are presented.     

To what extent do Gestalt grouping principles influence tactile perception?

Since their formulation by the Gestalt movement more than a century ago, the principles of perceptual grouping have primarily been investigated in the visual modality and, to a lesser extent, in the auditory modality. The present review addresses the question of whether the same grouping principles also affect the perception of tactile stimuli. Although, to date, only a few studies have explicitly investigated the existence of Gestalt grouping principles in the tactile modality, we argue that many more studies have indirectly provided evidence relevant to this topic. Reviewing this body of research, we argue that similar principles to those reported previously in visual and auditory studies also govern the perceptual grouping of tactile stimuli. In particular, we highlight evidence showing that the principles of proximity, similarity, common fate, good continuation, and closure affect tactile perception in both unimodal and crossmodal settings. We also highlight that the grouping of tactile stimuli is often affected by visual and auditory information that happen to be presented simultaneously. Finally, we discuss the theoretical and applied benefits that might pertain to the further study of Gestalt principles operating in both unisensory and multisensory tactile perception.     

Tactile orientation constancy: Do proprioception and attention affect the tactile vertical?1

Abstract: Tactile vertical, defined as the edge orientation that participants perceive to be vertical, was examined in four experiments. In Experiment 1, we touched the participants’ cheek, lips, or hand with an edge and asked them to judge its orientation with regard to gravitational vertical, both when the stimulated body part was upright (or, in the case of the lips, aligned), and when it was tilted (lips, distorted). We found that when the head or hand was tilted forward 30°, or when the lower lip was distorted approximately 38° to the left or right, the tactile vertical shifted in the same direction by only a fraction (8.7, 8.6, and 36.3% for the cheek, lips, and hand, respectively) of the change in orientation of the stimulated region. The results indicated considerable, but usually incomplete, orientation constancy. In Experiment 2, we measured tactile vertical on the hand for forward tilts from 0° to 45°. We found that as the hand was tilted, the tactile vertical increasingly shifted in the same direction as the hand (i.e., a tactile Aubert effect). In Experiment 3, the effect of attentional focus on tactile vertical was examined by comparing the tactile vertical of participants who attended to body‐centered coordinates, and others who attended to gravitation‐centered coordinates. We found that focusing on body‐centered coordinates caused a decrease in orientation constancy. We sought to examine the role of attention further in Experiment 4, measuring tactile vertical on the cheek of persons with temporomandibular disorders. Compared with normal participants, these participants displayed significantly lower constancy. The results were accounted for by a narrowing of attention to painful signals, so that proprioceptive information was attended to less. In conclusion, the degree of tactile orientation constancy that participants demonstrate varies as a function of body site and attentional focus.     

Can tactile stimuli be subitised? An unresolved controversy within the literature on numerosity judgments

There is a growing interest in the question whether the phenomenon of subitising (fast and accurate detection of fewer than 4-5 stimuli presented simultaneously), widely thought to affect numerosity judgments in vision, can also affect the processing of tactile stimuli. In a recent study, in which multiple tactile stimuli were simultaneously presented across the body surface, Gallace et al (2006 Perception 35 247-266) concluded that tactile stimuli cannot be subitised. By contrast, Riggs et al (2006 Psychological Science 17 271 275), who presented tactile stimuli to participants' fingertips, came to precisely the opposite conclusion, arguing instead that subitising does occur in touch. Here, we re-analyse the data from both studies using more powerful statistical procedures. We show that Riggs et al's error data do not offer strong support for the subitising account and, what is more, Gallace et al's data are not entirely compatible with a linear model account of numerosity judgments in humans either. We then report an experiment in which we compare numerosity judgments for stimuli presented on the fingertips with those for stimuli presented on the rest of the body surface. The results show no major differences between the fingers and the rest of the body, and an absence of subitising in either condition. On the basis of these observations, we discuss whether the purported existence of subitisation in touch reflects a genuine cognitive phenomenon, or whether, instead, it may reflect a bias in the interpretation of the particular psychometric functions that happen to have been chosen by researchers to fit their data.     

Lost in the move? Secondary task performance impairs tactile change detection on the body

Change blindness, the surprising inability of people to detect significant changes between consecutively-presented visual displays, has recently been shown to affect tactile perception as well. Visual change blindness has been observed during saccades and eye blinks, conditions under which people’s awareness of visual information is temporarily suppressed. In the present study, we demonstrate change blindness for suprathreshold tactile stimuli resulting from the execution of a secondary task requiring bodily movement. In Experiment 1, the ability of participants to detect changes between two sequentially-presented vibrotactile patterns delivered on their arms and legs was compared while they performed a secondary task consisting of either the execution of a movement with the right arm toward a visual target or the verbal identification of the target side. The results demonstrated that a motor response gave rise to the largest drop in perceptual sensitivity (as measured by changes in d′) in detecting changes to the tactile display. In Experiment 2, we replicated these results under conditions in which the participants had to detect tactile changes while turning a steering wheel instead. These findings are discussed in terms of the role played by bodily movements, sensory suppression, and higher order information processing in modulating people’s awareness of tactile information across the body surface.     

Effectively responding to tactile stimulation: Do homologous cue and effector locations really matter?

We report a study designed to investigate the extent to which speeded behavioral responses following tactile stimulation are influenced by differences in neural conduction latencies at different body sites and/or by the characteristics of the compatibility between the cue and effector. The results showed that it may not be particularly desirable to present tactile cues (e.g., warning signals) to an interface operator's feet if a speeded foot response is required, for even though such an arrangement maximizes the set-level compatibility between the stimulus and the response, it turns out that response latencies are primarily determined by conduction latencies through the peripheral nervous system.     

Within-hemifield posture changes affect tactile–visual exogenous spatial cueing without spatial precision,especially in the dark

We investigated the effects of seen and unseen within-hemifield posture changes on crossmodal visual–tactile links in covert spatial attention. In all experiments, a spatially nonpredictive tactile cue was presented to the left or the right hand, with the two hands placed symmetrically across the midline. Shortly after a tactile cue, a visual target appeared at one of two eccentricities within either of the hemifields. For half of the trial blocks, the hands were aligned with the inner visual target locations, and for the remainder, the hands were aligned with the outer target locations. In Experiments 1 and 2, the inner and outer eccentricities were 17.5º and 52.5º, respectively. In Experiment 1, the arms were completely covered, and visual up–down judgments were better when on the same side as the preceding tactile cue. Cueing effects were not significantly affected by hand or target alignment. In Experiment 2, the arms were in view, and now some target responses were affected by cue alignment: Cueing for outer targets was only significant when the hands were aligned with them. In Experiment 3, we tested whether any unseen posture changes could alter the cueing effects, by widely separating the inner and outer target eccentricities (now 10º and 86º). In this case, hand alignment did affect some of the cueing effects: Cueing for outer targets was now only significant when the hands were in the outer position. Although these results confirm that proprioception can, in some cases, influence tactile–visual links in exogenous spatial attention, they also show that spatial precision is severely limited, especially when posture is unseen.     

Mothers’ and fathers’ early tactile contact behaviors during triadic and dyadic parent-infant interactions immediately after birth and at 3-months postpartum: Implications for early care behaviors and intervention

Mothers’ and fathers’ touch were investigated during their first naturalistic interaction with their newborns, and maternal touch was predicted from newborn to 3-months postpartum during the Still-Face (SF) procedure. Both parents displayed more nurturing types of touch when interacting with their infants for the first time. Maternal touch at newborn predicted maternal touch after, but not before, the SF 3-months later; more touch after birth was associated with more soothing, regulating, types of maternal touch following the SF, suggesting that the nature of these interactive contexts (post-birth, post-SF) may be parallel. To our knowledge, this is the first study to investigate the full range of maternal and paternal touching behaviors during the first hour after birth. It is also one of the only investigations that considers how mothers’ very first touch and physical contact relate to their later touch at 3-months. Our results uniquely contribute by revealing the nurturing and predictive quality of parents’ touch, and underscore touch as a primary means of early contact and communication.