Learning to produce and transcribe cardinal vowels: speech and language therapy students’ perception of task difficulty

Figures & data

Table 1. PDP and PDT counts and percent by CV and CV articulatory classification used in the logistic regression modelling.

CV		Front	Open	Lips	CVSet	PDP	%PDP	PDT	%PDT
1	[i]	FRONT	CLOSE	SPREAD	PRIMARY	0	0%	4	3%
2	[e]	FRONT	CLOSE-MID	SPREAD	PRIMARY	39	28%	50	36%
3	[ɛ]	FRONT	OPEN-MID	NEUTRAL	PRIMARY	19	14%	43	31%
4	[a]	FRONT	OPEN	NEUTRAL	PRIMARY	4	3%	15	11%
5	[ɑ]	BACK	OPEN	NEUTRAL	PRIMARY	14	10%	20	14%
6	[ɔ]	BACK	OPEN-MID	ROUNDED	PRIMARY	32	23%	51	37%
7	[o]	BACK	CLOSE-MID	ROUNDED	PRIMARY	37	27%	58	42%
8	[u]	BACK	CLOSE	ROUNDED	PRIMARY	12	9%	18	13%
9	[y]	FRONT	CLOSE	ROUNDED	SECONDARY	34	24%	24	17%
10	[ø]	FRONT	CLOSE-MID	ROUNDED	SECONDARY	70	50%	73	53%
11	[œ]	FRONT	OPEN-MID	ROUNDED	SECONDARY	65	47%	66	47%
16	[ɯ]	BACK	CLOSE	SPREAD	SECONDARY	74	53%	26	19%

Figure 1. Mean PDP for production for each CV in decreasing order. The pareto line shows cumulative PD.

Figure 2. Boxplots of PDP by articulatory classification: (a) frontness, (b) openness, (c) lip posture and (d) CVSet.

Figure 3. Odds ratio plot illustrating the effect of CV features on PDP in the full model. FRT = front, BCK = back, CL = close, CM = close-mid, OM = open-mid, OP = open, SPR = spread, NTR = neutral, RND = rounded, PRM = primary CV, SCD = secondary CV.

Table 2. Output of logistic regression full model for PDP. The intercept is the front close spread CV1 [i].

	Log Odds (β)	Odds Ratio (e^β)	SE	z-value	p-value
Intercept	−2.85	0.06	0.29	−12.44	<0.001
Front-BACK	0.95	2.59	0.16	6.08	<0.001
Open-CLOSE-MID	1.59	4.90	0.19	8.20	<0.001
Open-OPEN-MID	1.29	3.63	0.21	6.13	<0.001
Open-OPEN	−0.11	0.90	0.41	−0.26	0.79
Lips-NEUTRAL	−0.29	0.74	0.35	−0.83	0.41
Lips-ROUNDED	−0.61	0.54	0.17	−3.57	<0.001
CVSet-SECONDARY	2.05	7.77	0.17	12.18	<0.001

Table 3. Comparison of null model, simplified model and full model for PDP.

	AIC	LogLik	dF	χ^2 p-value	VIF
Null model	1839.7	−918.83	N/A	<0.001	N/A
Full model	1565.5	−774.77	7	<0.001	Front 1.49 Open 4.27 Lips 3.77 CVSet 1.78
Simplified model	1575.1	−781.54	5	<0.001	Front 1.35 Open 1.38 CVSet 1.51

Figure 4. Mean PDT for production for each CV in decreasing order. The pareto line shows cumulative PDT.

Figure 5. Boxplots of PDT by articulatory classification: (a) frontness, (b) openness, (c) lip posture, and (d) CVSet.

Figure 6. Odds ratio plot illustrating the effect of CV features on PDT in the full model. FRT = front, BCK = back, CL = close, CM = close-mid, OM = open-mid, OP = open, SPR = spread, NTR = neutral, RND = rounded, PRM = primary CV, SCD = secondary CV.

Table 4. Output of logistic regression full model for PDT. The intercept is the front close spread CV1 [i].

	Log Odds (β)	Odds Ratio (e^β)	SE	z-value	p-value
Intercept	−2.61	0.07	0.21	−12.54	<0.001
Front-BACK	0.35	1.42	0.15	2.30	0.02
Open-CLOSE-MID	1.86	6.42	0.18	10.10	<0.001
Open-OPEN-MID	1.58	4.85	0.20	7.81	<0.001
Open-OPEN	0.26	3.53	0.33	0.78	0.43
Lips-NEUTRAL	0.23	1.26	0.29	0.80	0.42
Lips-ROUNDED	0.14	1.15	0.18	0.80	0.42
CVSet-SECONDARY	0.79	2.20	0.17	4.68	<0.001

Table 5. Comparison of null model, simplified model, and full model for PDT.

	AIC	LL	df	χ^2 p-value	VIF
Null model		−970.52	N/A	<0.001	N/A
Full model	1747.4	−865.70	7	<0.001	Front 1.65 Open 3.87 Lips 4.33 CVSet 1.90
Simplified model	1744.3	−866.14	5	<0.001	Front 1.22 Open 1.25 CVSet 1.34

Figure 7. Cluster dendrogram.

Data availability statement

The data that support the findings of this study are available from the author upon reasonable request.