4.1.1. Participants
43 participants (8 male and 12 female in the human cue condition; 9 male and 14 female in the physical cue condition) were recruited from UCL’s participant pool. Two UCL students were recruited to play the speaker role.
These students were blind to purpose of the study. All were paid or given course credit for their participation.
4.1.2. Stimuli and design
Participants were given instructions to move objects around a 3*3 grid as in Figure 2.2 above, where three objects were in common ground between the instructing speaker and hearer and three objects were placed in grid positions so that they were only visible to the hearer (privileged ground).
Except for the training phase where participants were given a turn at being director, all instructions were given by a confederate speaker. These instructions were pre-recorded in a single session with each of the two confederates who worked on the study. Thus each participant in a given set of conditions heard the same pre-recorded instructions.
For each trial, a new set of objects appeared on the display. Each such set contained objects belonging to one of three categories: fruit, animals or geometric shapes. There were ten different pictures for each category and some were paired in the same subtypes. For example, among the fruits, there were two apples, two bananas, and two oranges.
Six pictures were randomly chosen for each trial of the experiment, except for the competitor condition where two pictures from the same subtypes were presented. For instance, competitor condition item might contain a picture of a banana, cherries, grapes, an orange, and two different apples,
while for the matched non-competitor condition one of the twinned objects was replaced by a new object, for example, a strawberry (Fig. 2.3).
A trial consisted of one instruction where the participant was asked to move an object to a location. For example, ‘Move the apple to the bottom middle’. There were 24 critical trials and 24 filler items in each association condition. In 12 critical trials (competitor condition), the privileged objects included one that was the same type as (although not visually identical to) the target in the instruction (an apple). In the other 12 critical trials (non-competitor distractor condition), no privileged object was of the same type as the target object. Figure 2.3 below shows initial set ups for a pair of trials in competitor and non-competitor conditions.
Figure 2. 3. The initial display for the competitor condition (left) and non-competitor condition (right) in Experiment 1.
In this example, the target green apple had competitor with the same subtype, e.g.
a red apple, (competitor condition) or an irrelevant non-competitor, e.g. a strawberry, (non-competitor) in participants' privileged grid.
The 24 filler items involved location-based instructions, ‘Move the one in the bottom left to the middle right’. In a homogeneous association condition, all 48 instructions were targeted at objects in common ground. In a heterogeneous condition, 18 of the 24 location-based filler instructions were targeted at privileged ground objects.
Association was operationalized in two different ways in a between groups cue-type manipulation. In a social-cue condition, two different speakers (one male, one female) gave instructions in the same session.
One speaker gave instructions that referred to common ground objects only (homogeneous condition) and one speaker gave instructions that referred to both common and privileged ground objects (heterogeneous condition). The gender of the speaker in each condition was counterbalanced across the experiment. In a physical-cue condition, one speaker gave all 96 instructions for the session. For half the instructions, the frame showing the speaker had a yellow border and individual instructions were preceded by a ringing sound, while half the instructions had the speaker’s image in a green border and a distinctively different buzzing sound preceded them. One set of these physical cues accompanied homogeneous instructions while the other set accompanied the heterogeneous instructions. These were counterbalanced across the experiment.
To sum up, the experiment had a 2 (competitor) * 2 (association) * 2 (cue type) design. Altogether, each session with a participant involved 96 trials, 48 delivered in the homogeneous and 48 in the heterogeneous condition. The order of presentation of trials was randomised. Cue-type was a between subjects manipulation. So a participant either had instructions from two different people (social-cue condition) or one person but with two sets of colours and sounds (physical cue).
4.1.3. Procedure
In each session, a participant was seated in front of a 17” screen fitted with Tobii X60 eye-tracking equipment in a room with only the experimenter.
They were told that they would be interacting with a person located in another part of the college via a video link. Prior to a training phase, participants were given some initial instructions. All instructions were given verbally by one of the confederate speakers via video appearing on the monitor in front of the participant. The speakers told the participants that they would play a game where they should follow the speaker’s instructions to move objects around a grid. They were then shown how the screen would be set up at the beginning of each trial. See Figure 2.4.a.
In figure 2.4.a, the 3*3 grid appears on the left of the screen. It is empty. On the right there is a shelf which contains three objects. In the training phase at the beginning of a session, the speaker tells the participant that these are their private objects that she/he does not know what they are or care what they are. The speaker instructs the participant that they should move these objects to the private positions on the 3*3 grid and then click on the image of the speaker in the top right hand corner of the screen when they are ready. When the participant has completed this task, they click on the image of the instructor and a bell sound is hear. The instructor then makes three objects appear in common view on the grid.
The visual display now appears as in Figure 2.4.b. The instructor then gives one instruction to move an object to a new location. When this is completed by the participant, they click the ‘NEXT’ button on the bottom right of the screen and the whole procedure begins again for the next trial.
In the next part of the training phase, the participant experienced a few trials from the instructor’s perspective. They saw the empty grid with three blocked-off shelves, as in Figure 2.4c. Then they heard a bell sound and clickd “SHOW”. Then the common objects appear. One object is marked with a red star and one of the empty grid positions is marked with a
blue star. Participants are instructed to tell the other person to move the marked object to the marked empty position. This part of the training procedure ensures that participants understand that the instructor does not see the common objects.
The participant then returns to the role of the listener and the experiment begins. Note that, on each new trial, the three private grid positions appeared in different, randomly assigned locations around the nine frame grid. After every two or three trials, participants had an opportunity to break prior to re-calibration of the eye-tracking equipment.
Note also that the trial order was fixed across both groups. It was constructed using a randomised order except that three location-based fillers were placed among the first ten trials, prior to the occurrence of the first heterogeneous test trial.
a. b.
c.
Figure 2. 4. The initial procedure for each trial in Experiment 1.
Participants were firstly required to move three objects from their private small grid to the three private grey frames in the big grids (a), then three common objects were shown in the transparent frames (b.). A prior training phase involved the participant taking the instructor’s role. They see the grid as in (c) initially prior to hearing a bell sound, at which point they click, ‘SHOW’.