3. Staff costs

Included in research and development expenses:

	2017		2016		2015
	(in thousands)
	£		£		£
Wages and salaries		2,391		2,241		1,366
Social security costs		272		205		151
Pension costs and other benefits		119		102		92
Share-based payments		8,868		1,027		709
		11,650		3,575		2,318

Included in administrative expenses:

	2017		2016		2015
	(in thousands)
	£		£		£
Wages and salaries		408		84		108
Social security costs		37		13		52
Pension costs and other benefits		21		7		15
Share-based payments		2,863		105		76
		3,329		209		251
Total employee benefit expense		14,979		3,784		2,569

The average number of staff employed under contracts of service were:

	2017		2016		2015
	(number)
Research and development activities		18		15		11
Administrative activities		2		1		1
		20		16		12

Directors’ remuneration & other benefits

The number of directors who exercised share options in 2017 is nil (2016: 1; 2015: nil).

The above amounts for remuneration include the following in respect of the highest paid director: