Table 1.

Studies on the effects of chewing on attention.

Study	Cognitive tests and psychological rating scales	Chewing objects	Summary of results (compared with nonchewing condition unless stated)	Attributes of effects on attention
Wilkinson et al. (2002) [10]	15 tests on memory and attention	Sugar-free spearmint gum	Improvements of scores on episode and working memory and simple reaction time. Elevation of heart rate. No significant differences in attention.	Not significant
Tucha et al. (2004) [11]	12 tests on memory and attention	Sugar-free spearmint gum and sugar-free tasteless gum	Shortening of reaction time on sustained attention, prolongation of reaction time on alertness, and increase of number of errors on flexibility. No significant differences in memory and pulse rate.	Positive or negative depending on task
Stephens and Tunney (2004) [37]	8 tests on memory and attention	Sugar-free mint flavored gum	Improvements of scores on episode and working memory, attention, and processing speed. No significant differences in executive function.	Positive
Kohler et al. (2006) [36]	Psychomotor vigilance, tracking, and grammatical reasoning and alertness	Parafilm (sugar-free, tasteless)	Not significant or detrition of performance of speed and accuracy on simple and complex cognitive tasks except for a simple motor tracking task early during the period of sleep deprivation. No significant differences in alertness, heart rate, and root mean square of successive differences in R-R intervals.	Positive or negative depending on task and time
Sakamoto et al. (2009) [15]	Reaction time	Odorless and tasteless gum base	Shortening of reaction time and the peak latencies of event-related potentials (P300 and N100) in second and third session after chewing.	Positive
Smith (2009) [16]	Mood, alertness, intelligence test, and short term and working memory	Volunteer's preferred gum	Improvement of intelligence test. No significant difference in memory. Increased alertness at the end of the test session.	Positive
Scholey et al. (2009) [21]	4 tests including memory, attention, and mood	Volunteer's preferred gum	Overall better performance on the cognitive tasks. Increase of alertness and reduction of stress and salivary cortisol.	Positive
Smith (2009) [18]	5 tests on alertness and mood	Caffeinated gum or placebo gum	More positive mood after chewing and at the end of the study regardless of caffeine. Higher alertness after chewing. No significant difference in alertness without caffeine.	Not significant
Sakamoto et al. (2009) [14]	Reaction time	Odorless and tasteless gum base	Shortened reaction time at third trials after chewing. Increased contingent negative variation (CNV) at second and third trials after chewing. No significant differences in movement-related control potentials.	Positive
Tänzer et al. (2009) [30]	16-minute concentration test	Sugar-free fruit gum	Improvement of concentration performance with time in 8-9-year-olds.	Positive
Smith (2010) [17]	10 tests on memory, attention, and mood	Spearmint or fruit gum	Improvement of alertness and selective and sustained attention. Shortened reaction time; this effect became bigger as the task became more difficult. Increase of heart rate and saliva cortisol.	Positive
Tucha et al. (2010) [42]	Vigilance and sustained attention	Sugar-free spearmint gum	Deterioration of vigilance performance in both healthy children and children with ADHD (mean age 10.8 years). No significant difference in sustained attention.	Negative
Tucha and Simpson (2011) [29]	Sustained attention	Sugar-free spearmint gum	Detriment on sustained attention in earlier stages of 30-minute task and benefit on sustained attention at later stages.	Negative early to positive later within 30-min period
Johnson et al. (2011) [25]	4 tasks including memory and attention, mood, and alertness	Regular chewing gum	Increase of self-rated alertness and stress. No significant differences in task performance and saliva cortisol.	Positive
Onyper et al. (2011) [41]	5 tasks including memory and attention	Spearmint or doublemint gum with or without sugar	Improvements of performance of several tasks in chewing for 5 minutes prior to testing. No significant differences in chewing throughout testing.	Positive in chewing prior to testing
Sketchley-Kaye et al. (2011) [26]	Acute stress task, mood, anxiety, and alertness	Regular chewing gum	Attenuation of state anxiety and increase of alertness under condition of acute social stress task. No significant differences in contentedness or calmness.	Positive
Allen and Smith (2012) [31]	4 tasks on attention and mood	Volunteer's preferred gum	Increased alertness, mood, and performance of attention test and shortened reaction time. Initial extended vigilance reaction times were shortened after trials.	Positive, but some tests showed negative effects initially
Allen and Smith (2012) [38]	4 tasks on attention and mood	Volunteer's preferred gum	Increased reported alertness for positive and neutral demand characteristics. Improved selective attention. Reduced performances of two attention tasks only at specific time of trials. Better response organization on categoric search task when demand characteristics and pretest attitudes to gum were both negative.	Positive, but some tests showed negative effects at specific time of trials
Hirano et al. (2013) [12]	Alerting and executive control	Odorless and tasteless gum base	Shortened reaction time. No significant differences in alerting and conflict effects. Higher activations in the anterior cingulate cortex and left frontal gyrus for the executive network and motor-related regions for both attentional networks	Positive
Johnson et al. (2013) [28]	Sustained attention, alertness, and mood	Cool Breeze gum	Improved attentional task performance. Higher alertness and mood. Shortened response times. No time-on-task effect.	Positive
Morgan et al. (2014) [32]	Short-term memory, vigilance, and mood	Sugar-free spearmint gum	Attenuated time-dependent decrement on both performance and subjective alertness. Shorter correct reaction time in the latter stage of the task.	Positive, especially in the latter stage of the task
Allen et al. (2014) [35]	Vigilance and mood	Gum base	Shortened reaction time and increased rate of hits. Heightened heart rate during chewing. Increased EEG beta power at F7 and T3 immediately after chewing.	Positive