## 2 Materials and Methods  
In 2002, scientists discovered a new type of photoreceptor--intrinsically photoreceptive retinal ganglion cells (ipRGCs), which play an important role in the nonvisual responses to light [27]. However, the action spectrum of ipRGCs alone is insufficient to assess the magnitude of nonvisual responses to light because the firing rate of ipRGCs is also influenced by the four other types of photoreceptors--rods, S-cones, M-cones and L-cones. Thus, the International Commission on Illumination (CIE) developed a light measurement system in which the responses of all five photoreceptor types are characterised to assess nonvisual responses to light [28]. The CIE recommended that spectral measurements, in the form of spectral irradiance distributions (SIDs), be carefully collected and recorded for research relating to the circadian effects of light [29]. In this study, SIDs were collected in various interior spaces, including open plan and cellular offices in six commercial buildings, as well as home offices in four residential buildings. In these applications, users typically sit at desks and face computer displays. The environment (e.g., positions of window shading devices, furniture layouts) remained as it was during the typical use of these spaces. Spectral irradiance distributions were measured from a position equivalent to the front of an eye of a seated occupant. To do so, a spectral irradiance meter (Konica Minolta CL-500A) was mounted approximately 30 cm above the desk surface on an adjustable chin rest, which was installed at the edge of each desk. Daylight was measured with the interior electric lights switched off. The measurements were conducted automatically every ten minutes. Measurements of electric lighting were conducted at night, and the window coverings were closed if there was any light from external lighting sources. Because the spectrum of electric light is relatively stable, the SIDs for illumination from electric light were measured three times for each condition. For the spectrally tuneable lighting system, SIDs were collected under three control settings: warm white light (measured 2762 K), neutral white light (measured 3968 K), and cool white light (measured 6253 K). Laptop and desktop computers from different manufacturers were used in this study to generally understand the effects of currently commercially available displays. The spectrum of light emitted from a display is highly dependent on the tasks undertaken on the computer. A variety of different computer tasks were conducted when the SIDs were recorded in five-minute measurement intervals. Typical computer tasks in offices include website browsing, word processing, reading, writing emails, etc. Some industries, such as architectural design, involve the use of design software with default black backgrounds. In home offices, computer displays also commonly perform some recreational activities, such as streaming videos. Thus, the SIDs were measured separately when typical office tasks were simulated, when black-background software was used, and when videos were displayed. To account for changes in the spectrum over time, the measurements of displays were taken for between one and five hours. In total, 394 SIDs at eye height were collected when only daylight was measured, 80 SIDs were collected under solely electric light, and 134 SIDs were recorded of the light solely from computer screens. The \(\alpha\)-optic irradiance was calculated for each measurement condition using Equation (1), as recommended in CIE DIS 026/E:2018 [28],  
\[E_{e,\kappa}=\int E_{e,\lambda}\ (\lambda)S_{\kappa}(\lambda)\ d\lambda \tag{1}\]where \(E_{e\lambda}\left(\lambda\right)\) is the spectral irradiance at a point in space, \(S_{\alpha}(\lambda)\) is the \(\alpha\)-optic action spectrum defined by CIE, and \(E_{e,\alpha}\) is the effective photobiological irradiance at the point in space.