74 BARRETT, EDMONDSON-JONES, HALL level. Loudspeakers were mounted on a flat metal frame (height 150 cm, width 150 cm) supported off the floor by two metal legs. Each loudspeaker was located at an eccentricity of 0°, 17°, and 34° to either side of the fixa- tion point, providing one position on the vertical mid- line, two in the left hemispace, and two in the right. A sheet of white fabric was stretched across the metal frame to cover the loudspeakers and to prevent any visual cues about their position. Participants sat in front of this screen at a viewing distance of 1,100 mm. Visual stimuli were projected from a ceiling-mounted projector (NEC WT610) onto the screen at precisely the same positions as the loudspeakers. Visual targets were the same size as the loudspeakers, and visual and auditory stimuli were pre- sented at exactly the same location in extrapersonal space. A fixation cross was projected immediately below the horizontal midline and remained on the screen throughout each trial. Stimulus presentation was con- trolled using customized software running on a Viglen PC equipped with a standard graphics card and a Motu 24 I/O sound card. Verbal responses were coded and entered into the computer by the experimenter. Procedure Ethical approval for the study was granted by the Not- tingham committee of the National Health Research Ethics Board, and written consent was obtained from all participants. Testing comprised the clinical assessment and the two experimental tasks. Clinical assessments were carried out on the ward while experimental tasks were conducted in a sound-attenuated booth at the Ear, Nose, and Throat department. For the patients, assess- ment and experimental tasks were carried out on consec- utive days with cancellation and visual confrontation tasks repeated on the final day of testing. Controls com- pleted all of their testing within a single session in the sound-attenuated booth. Visual and auditory versions of the extinction and TOJ tasks were presented in separate blocks, with the order counterbalanced across participants. Once the participant was ready, trials were initiated by the experimenter and always started with fixation. In the extinction task, stimuli were presented singly or in a pair for one second. Single-target trials comprised an equal number of each stimulus (e.g., “ah” and “ee”). Dual-target trials always contained one of each stimulus (e.g., a blue square and a red circle) and were always pre- sented to locations separated by an angle of 34° (i.e., with one loudspeaker position between them). Single tar- gets were presented to each of the five horizontal loca- tions. Dual targets were presented to three spatial configurations in which the pair was (a) located in the right hemispace (RH), (b) across the central meridian (CM) or (c) located in the left hemispace (LH; Figure 2). Stimulus type, location, and number of single- and dual- target trials (12 within each spatial configuration) were sampled with equal probability in each task. Trials were presented in a random order. Participants were asked to report the number of targets (one or two), but were not required to identify them. Responses were, therefore, orthogonal to the location of the stimuli in order to negate any confounds associated with a spatially medi- ated response bias. In the TOJ task, the pair of targets (e.g., blue square and red circle) was always presented at an eccentricity of 17° in the left and right hemifields (i.e., separated by a fixed angle of 34°). The stimulus onset asynchrony (SOA) between the two targets could take the following values: 1, 50, 100, 150, 200, 250, 300, and 400 ms. The side and order in which each stimulus type was presented were counterbalanced. Six right- and six left-first target trials occurred at each location for all SOAs. This method of constant stimuli provided a spread of data that was sufficient to plot individual psychometric func- tions. The offset of the pair of targets was simultaneous, and the first stimulus was always presented for a total of one second. Both the SOA and the side on which the tar- get first appeared were randomized. Participants indi- cated verbally which of the two targets appeared first by reporting its identity. Again, participants were required to report a stimulus attribute (identity) that was orthog- onal to the location to which stimuli were presented (Shore & Spence, 2005). Analyses: Extinction task To assess the effect of eccentricity, the proportion of correctly detected single-target trials was entered into contingency tables for each participant. Trial outcome (0 = incorrect, 1 = correct) was entered as the depend- ent variable and eccentricity (–34°, –17°, 0°, 17°, 34°) as Figure 2. The left-hand panel illustrates the dual-target conditions in the extinction task. Dual targets were presented to the left hemis- pace (LH), to the right hemispace (RH), and across the central meridian (CM). Single targets were presented to each of the five loca- tions. The visual angles correspond to the five locations at which stimuli were presented. The right-hand panel presents a schematic of the temporal order judgment (TOJ) task. Two stimuli were always presented at a fixed eccentricity of ±17°. Stimulus onset asynchronies (SOAs) varied between 0 and 400 ms.