The tickly homunculus and the origins of spontaneous sensations arising on the hands

Activity Resource [Re-mapping the senses workshop]

Materials
A4 Paper with hand printed at half size, Antiseptic gel, Red Dot, or similar 5cm diameter

1- Clean hands with antiseptic gel. Place Red disk and paper on the table. Place one hand on A4 paper and the other hand under a table on the knee.

2- Focus on hand for 10s /  either / or try both …
Convergent focussing [looking at the hand while focussing on the hand]
Divergent focussing [looking at red disk while focussing on the hand]

3 Map any sensations onto a map of the hand. Discuss these and describe as a group.

From original paper discussing the experimental method…
“ Subjects were divided up for the tests into groups of 4–5 in a quiet room with an ambient temperature of 22–26 °C…all subjects were required to spend 15 s cleaning their hands with an antiseptic gel used for medical purposes (AniosgelÒ 85 NPC, 3 ml per participant). … The experimenter placed a sheet of smooth paper (every day, white, 120 g, 21 29.7 cm) and a wooden red disk (5 cm diameter) on each table and announced the beginning of the testing session. Subjects were required to put the disk on one side as referred to their body midline and the sheet of paper on the other side.

The tested hand was placed palm-down on the paper, without any pressure and with the fingers slightly apart. The other hand was placed on their knee.

Two variables were manipulated, the tested hand and the focusing condition. Convergent focusing refers to the condition where subjects were looking at their hand and focusing their attention on it, whilst divergent focusing refers to the condition where they were looking at the red disk while focusing their attention on the tested hand (Fig. 1). Thus, four separate conditions were tested: (a) convergent focusing left hand, (b) convergent focusing right hand, (c) divergent focusing left hand, and (d) divergent focusing right hand. All of the subjects completed all four conditions, which were balanced in a latin-square order.

A trial began with a ‘‘start’’ signal given verbally by the experimenter, following which participants directed their gaze towards their exposed hand or the red disk and kept it in that direction for a period of 10 s. During this time, subjects focused and retained their attention on the tested hand so as to detect and report any sensations that might occur, but were also informed of the possibility that no sensations would occur. The experimenter signalled the end of this period with a ‘‘stop’’ signal.Subjects were then immediately asked to indicate whether or not they had detected any sensations in the tested hand. In the affirmative, they had to (a) map the extent and topography of the sensations by shading the areas where sensations had occurred on a standardized half-size picture of the hand (the distance between the tip of the middle finger and palm/wrist frontier was 12.3 cm), a procedure adapted and expanded from Ochoa and Torebjörk (1983); (b) estimate their overall perceived intensity on a 10-point scale (1 = just perceptible; 10 = very intense but not painful). They were also told that if they could attribute different intensities to different sensations they were free to do so; and (c) identify the sensations using a list of descriptors based on the lists used by Ochoa and Torebjörk (1983), Macefield et al. (1990) and Naveteur et al. (2005), and with the possibility of course of choosing more than one of them: beat/pulse, itch, tickle, numbness, skin stretch, tingle, warming, cooling, muscular stiffness, flutter, and vibration. (Michael and Naveteur 2011)

Michael, G. A. & J. Naveteur (2011) The tickly homunculus and the origins of spontaneous sensations arising on the hands. Conscious Cogn, 20, 603-17.

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