*2.1. Participants*

Participants were recruited between 1996 and 2004 through personal visits to families living in both rural and urban areas of Nicaragua who were recruited via community contacts (see Table 2 for a summary of demographic information; see Gagne (2017) for more detailed information about the homesigners and their linguistic and educational experiences). The participants included eleven deaf homesigners (4 female, 7 male), aged 9 to 35 years at the time of testing. The homesigners had little to no formal education in written or spoken Spanish or Lengua de Señas Nicaragüense (NSL). Homesigners were further classified as either adult homesigners (4 participants, age 26 to 35) or child/adolescent homesigners (7 participants, age 9 to 14).

**Table 2.** Demographic information.


A second set of participants were the 24 communication partners of these deaf homesigners (12 female, 12 male), who were aged 9 to 64 years at the time of testing. Communication partners (CPs) were defined as hearing family members and friends who had regular contact with and communicated frequently with one of the homesigner participants. All of the communication partners were native Spanish speakers who had no experience with any sign language and who were familiar with the homesign system used in their family.

The third set of participants included 8 hearing non-signing adults (4 female, 4 male) aged 20 to 52 at the time of testing. All of the hearing non-signing adults were native Spanish speakers with no regular experience with any sign language or homesign system.

The participants were grouped into 9 homesigning families (each family had only one homesigner), 1 hearing non-signing family made up of 4 members, and 1 group of 4 unrelated hearing non-signers. Note that the hearing non-signers who were from the same family did not have a homesigner in their family; further, none of the unrelated hearing non-signers had a homesigner in their families. Two homesigners who were in the original

study did not have any communication partners to complete this task and therefore were excluded from group analyses.

#### *2.2. Materials and Procedure*

Participants were shown a slideshow consisting of photographs of items and asked to label them. Specifically, participants were shown a slide featuring three exemplars of the same tool, such as a hammer, and then were asked to sign what it was. After the participant had finished responding to the current image, the experimenter would move on to the next slide. All data were collected between 2011 and 2012, and each session was videotaped. All participants were tested individually and signed their responses to the experimenter in order to avoid influencing the responses of other members of their family.

The stimuli presented were 27 images of different tools and instruments: 6 items of clothing (pair of shoes, jacket, sock, hat, glove, pants), 8 grooming/cosmetic items (hairbrush, nail file, mascara, comb, hairdryer, nail polish, toothbrush, lipstick), 3 utensils (fork, spoon, knife), 9 handheld tools (scissors, broom, hammer, paintbrush, rake, screwdriver, vacuum cleaner, handsaw, mop), and 1 other handheld item (cellphone). This set of stimuli was also used in Padden et al. (2015). Every participant was shown the stimuli in the same order via the slideshow.

#### *2.3. Transcription and Response Types*

The participants' signs and gestures were transcribed using ELAN (Wittenburg et al. 2006), a program that facilitates the coding of simultaneous aspects of gesture and sign language production that is aligned with the video content. Each sign was glossed and coded for handshape representation type for both hands. The relevant handshape types were *Handling* (Figure 1a), in which the handshape reflects how one would hold the tool, and *Object* (Figure 1b), in which the handshape depicts the shape or form of the actual tool itself. Other handshape representation types included *Handling–Object-Simultaneous,* in which the participant simultaneously produces a Handling handshape with one hand and an Object handshape with the other hand, and *Handling–Object-Sequential*, in which the handshape sequentially transitions from one representation type to another, which we collapsed into *Handling+Object* (Figure 1c). Signs marked as *Other* (i.e., not specifically in reference to the tool or not iconic) were not included in the analysis.

For each item response, only one handshape type was annotated. If participants made multiple iconic signs/gestures while labeling the item, the response selected for coding was simplified to note just Handling or just Object if all of the signs fell under one type, or Handling+Object if both types of signs were used. Therefore, each participant had a maximum response of 27 handshapes, which we were then able to use to calculate the percentage of iconic handshape types in order to determine preferences.

Finally, we describe the types of responses participants produced. Most people produced single gestures/signs, with the exception of adult homesigners who produced multiple signs more often (Table 3). Although participants were shown all 27 items and asked to label them, a few items were not familiar to the participants (e.g., vacuum cleaner) and they did not produce a response to them. Factoring in all of the participants, the total expected number of responses was 1161. However, we only included a total of 1035 responses, because not every participant produced a response for every item (e.g., some participants did not recognize the vacuum cleaner) or did not produce a relevant iconic response (e.g., the response was a pointing gesture).

**Figure 1.** Examples for responses of iconic handshape types: (**a**) Handling [mop], (**b**) Object [hand saw], and (**c**) Handling+Object [rake]. See supplementary materials to view video clips of responses.

**Table 3.** Percentage of responses that were a single sign/gesture versus multiple signs/gestures for each group. Most common response type for each group is bolded.

