Academic journal article Attention, Perception and Psychophysics

The Effects of Temporal Delay and Orientation on Haptic Object Recognition

Academic journal article Attention, Perception and Psychophysics

The Effects of Temporal Delay and Orientation on Haptic Object Recognition

Article excerpt

We examined the effects of interstimulus interval (ISI) and orientation changes on the haptic recognition of novel objects, using a sequential shape-matching task. The stimuli consisted of 36 wedge-shaped plastic objects that varied along two shape dimensions (hole/bump and dip/ridge). Two objects were presented at either the same orientation or a different orientation, separated by either a short (3-sec) ISI or a long (15-sec) ISI. In separate conditions, ISI was blocked or randomly intermixed. Participants ignored orientation changes and matched on shape alone. Although performance was better in the mixed condition, there were no other differences between conditions. There was no decline in performance at the long ISI. There were similar, marginally significant benefits to same-orientation matching for short and long ISIs. The results suggest that the perceptual object representations activated from haptic inputs are both stable, being maintained for at least 15 sec, and orientation sensitive.

Comparing objects haptically is something we do more often than we might think. Suppose, late at night, you arrive home and start to search for your front door key. It's too dark to see clearly, so you feel through the keys on your key ring and try a likely one. If it isn't the right one, you keep searching, trying to remember which keys you have already felt and the shape of the key that you are searching for. How effectively can we maintain these haptic memories of object shape over time?

One efficient solution for achieving such a goal might be for the haptic system to share the processes available for visual object recognition. Indeed, in many everyday situations, information from both modalities is combined to guide our actions, particularly when our goals require manipulating objects.

Converging evidence from a variety of methodologies has revealed broad similarities between vision and haptics. There is substantial overlap in the neural architecture invoked during visual and haptic object exploration (e.g., Amedi, Jacobson, Hendler, Malach, & Zohary, 2002; Amedi, Malach, Hendler, Peled, & Zohary, 2001; Miquée et al., 2008), and visual and haptic object recognition are similarly impaired by changes in object orientation (Craddock & Lawson, 2008; Lacey, Peters, & Sathian, 2007; Lawson, 1999, 2009; Newell, Ernst, Tjan, & Bülthoff, 2001) and object size (Craddock & Lawson, 2009a, 2009b).

Nevertheless, inputs from vision and haptics are not equivalent and must first traverse separate pathways; each modality will be subject to different limitations even if, ultimately, they share common perceptual representations. Although haptic object recognition is reasonably fast (e.g., Craddock & Lawson, 2008, 2009a; Klatzky, Lederman, & Metzger, 1985), it is generally slower than vision (e.g., Craddock & Lawson, 2009a). Haptics relies on slower, more sequential exploration than does vision and must, therefore, depend more on working and shortterm memory to maintain and integrate information as it accumulates. The haptic object-processing system should, therefore, be optimized for storing input over many seconds and, so, may be less sensitive to temporal delays than is vision. This was tested in a sequential object-matching study that varied interstimulus interval (ISI).

Previous studies examining the influence of ISI on tactile and haptic memory present somewhat mixed evidence. Nevertheless, there appears to be an important distinction between those experiments examining passive touch and those examining active, haptic exploration. Studies employing passive, tactile tasks reveal steadily declining memory as ISI increases. Three studies testing recall of the location of a tactile stimulus applied to the forearm after delays of 0-60 sec (Gilson & Baddeley, 1969; Miles & Borthwick, 1996; Sullivan & Turvey, 1972) reported worse performance as delay increased. Similarly, Gallace, Tan, Haggard, and Spence (2008) found that memory for tactile stimuli applied to multiple locations on the body simultaneously was worse at longer stimulus-probe delays. …

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